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Color-code multiple sessions defined within a Local network gateway automatically reconnect if showing where to. Some of the you to set a worm which can use our access CentralDispatch on without built-in PXE if you do. By continuing your limited by what and will continue a range of command line with.

Now jump to electronics You have a bunch of inverters connected in series. From data sheet you see time to change. Again using simple numbers, change takes You can still change input faster then this total delay, you just have to stay in the limits of a inverter. Now Your input changes fast, Inverter output might change faster or slower on output.

After inverters your nice fast square wave could look line a sign wave. A while back, lan. M talked about Schmitt input on logic. If the above inverters have Schmitt inputs, each would be doing it's little part in making that logic change faster. The sign wave output happens at a higher frequency.

Now replace the inverters with a non inverting buffer. You still have the delay! If you draw the clock signal the inverter input or buffer on paper and then make a copy on a transparency. You could number the changes see that current input is x newer then output Now the has a delay! As you add more clk inputs to 's the shout gets smaller.

One way to make shout work better is to do it when peak should happen on data input. First you have when a bit happens on output. Think of your first output chip replaced with a You would have to shift out bits for all output chips before getting to bits.

You would not do this as to update outputs you would also have to send 8 more bits after the output bits to get output bits in proper position. The design of chips have all shift registers stepping at same time. But always a but your input signal times must be good. If you add buffers in series you have to think about delays as shown in Inverters in series above. Now what could you do? With a big loop where you have buffer delays going out and the all the way back, you have a problem.

The cure is easy if you use clock out to sample the input bits. A SPI Master only has a send clock and not a send clock and receive clock. A SPI Slave only has a receive clock. The master generates the clock that the slave uses after delay. A simple step that removes OUT delay from picture. The timing at the SPI Master will be good, but you have to allow for the buffer delays working back.

Think of many transparencies stacked. The nice thing is that a slower clock rate removes the transparencies. Think of a computer reading memory. Data needs to be at computer to read. A miss of 10ns gives computer garbage. Speeding up memory or slowing computer by 15ns gives a 5ns safety margin and working computer.

Now to lan. M In is posts to this thread in answering your questions and making suggestions are a LOT of important details. I would suggest reading this thread many times and ask your self "why did he say that" I really like this one Quote. The following users thanked this post: Ian. I am going to work through the reply's one by one and over some time as I am researching all the valuable points made by each contributor.

Screen Shot at Edit: Thanks ilium, for switching to attached images. Preserved for posterity: First, for images less than the attachment size limits, its best to host them here as attachments. Otherwise anyone who wants to download or view the full sized image without the forum resizing it to fit the page has to wrestle with the external image hoisting site.

If you need to post an image inline to refer to it, attach it, post the post, then go back and edit the post IN A NEW TAB, so you can easily copy the link URLs of the non-expanded attachment thumbnails from the original tab, for inclusion in the IMG tags in your post.

Please don't inline large filesize images as it chews through Dave's hosting bandwidth and the user's download bandwidth every time someone opens that page of the topic. Them as wants to see them can simply click the attachment. Partial schematics are fine. When you draw the final one, for repeated stuff like inputs and relay circuits you can simply draw one channel in a block and indicate its repeated N times. The points each instance connects to should be named with a name that includes the instance number so you can see which connections 'belong' together.

Your first schematic is OK if the switches are on the same board as the CMOS chip and they have gold or carbon loaded elastomer contacts. If they have silver or other metal contacts, decrease R6 to 1K t get at least a few mA wetting current. If they are on a front panel, a 10K resistor between the board input and the top end of R6 and the CMOS input fpr at least minimal protection against transients and over-voltage. For the second circuit, if it isn't a Gold, mercury wetted or carbon loaded elastomer contact switch, you need that 1K resistor from the left end of R5 to ground to provide the wetting current.

That gives you a low pass filter with a 3dB corner frequency of 16KHz which should be enough to keep radio signals out of your inputs. If you are experiencing severe EMI issues, you could increase the capacitor to 10nF without any issues. With those mods, its designed to protect against the high impulse voltages that are commonly found around your layout. Now lets consider schematic three. The relays are switching motor power, not low current control signals. They do not need and should not have gold plated contacts as the plating wont stand up to high current arcing during opening or closing.

Solid Silver alloy contacts would probably be the most durable, though appropriately rated base metal contacts would come close. As they are switching significant current and voltage, they don't need any resistors for extra wetting current though RC snubbers which need to be calculated for the expected load current or 20V bidirectional TVS diodes across each contact pair would probably be advisable to reduce arcing and prolong the relay contact life.

It's probably worth putting a rightangle header on the Polulu motor driver board and a mating rightangle connector at the edge of your MCU board so they can plug directly together to minimise wiring. The driver output to the relays and the track wiring should use twisted pair of adequate gauge for the maximum current to minimise EMI so the motor PWM doesn't get into everything else. I would suggest using socketed relays mounted off-board - they'll be easier to wire and if one goes bad it will be cheap and easy to replace.

If you turn off the motor drive PWM before switching the relays you can get away with 5A ones. Edit: you missed the third image relays. I still had it cached so here it is. OK thanks - I'll fix up the image links. Looking at the other points made as well. I'm not sure what would happen if I were to only draw one of them. The voltage divider on 12V would supply 7. The pushbutton switches will connect to a front panel away from the input board. I think I will implement the voltage divider pending confirmation my 7.

I'm not a Kicad user, but it looks like you need to use hierarchical sheets to hold the block that you want to repeat. The Multiplying that by 2. M on November 25, , am. That's looking good apart from C8. Also, as a matter of style, please move the SER data in pin to the center of the left edge of the 74HC symbol. Then they will daisy-chain more clearly with the MCU board at the right hand end. That means the SPI control signals are breaking convention and going right to left, but its preferable to having the data flow backwards.

Its a pity the parallel input names don't include the bit number. I suggest annotating the symbol at the two end inputs with 'b0' and 'b7' SPI is transmitted MSB first, so get it the right way round! I did question myself when I put that cap there.

All I need to do now is find some appropriate poly fuses and get them on the diagram. It may or may not be of interest but here is Dads train layout and some of the very detailed Queensland Rail locos I am building this for!

Motor driver control of track blocks You have a computer so you could get real fancy if you can create correct code. You could control inputs of motor controller using logic. Using relays to control outputs You can find some relay boards that have single pole double throw relays SPDT Using these you could stop the train but un switched track side would still be swinging. Using DPDT you can switch both sides of track.

Now you could put a motor controller in place of Track in above example. Think of a checker board Horizontal rows are track blocks. Vertical rows columns are motor controller Using the relays you can increase the rows. The R1 prototype was useful to make and it's now the main board in one of my printers, but hand soldering the boards takes a while that's why only 5 people in the world have one :D.

Okay progress surprisingly faster than expected I finally got it sending one word at a time. The clock here isn't configured to run fast as it make things easier to debug. The remaining issue in this is that the WS clock should go high at the end of the word transmission to latch the shift registers. I tried to add some delay to the WS signal but from the looks of it it's limited to 3 cycles. One approach would be to send the right channel first so it's high and be able to set the idle state of the WS line to high.

EDIT: Using the gpio matrix we can invert the logic but it's still not right, as the data will be latched at the beginning and at the end of the transmission I have some ideas and you are much more skilled in programing than I. About the word clock. You could trigger it from the DMA state. The "old" word clock is just thrown away We are still getting 32 outputs out of four. Why not use the old word clock as an "Stepper is Running" pwm'ed status led?

About one word transfer: 3; Can we get the DMA to act as an ring buffer and just have "pushing" the data to the shift registers in the ring buffer all time as an loop. By doing it that way we will lose some time resolution but any "timer" triggered event for the stepper drive will just be a write to that ring buffer. A size of the buffer larger than a 32 bit word will add extra delay but should get more cpu cycles for other task and the delay will be constant and not add any time resolution jitter.

The optocouplers was not matched with the right resistors and that made them extremely slow. But that could also add some extra feature as we can "delay" a signal by using different resistors on the transistor output side. Opto coupling the outputs to the stepper driver would be nice anyway as then we are opening the usage for bigger stepper drivers and I might replace LinuxCNC with Marlin.

I hope that I can ramp up the DRV to 2 Amps and mill a new controller for my beefier stepper drivers. More progress on this end, and it's getting about close enough to be added to the HAL! So the plan for now is to keep it quite simple and use I2S pretty much as a GPIO expander simply allowing to toggle extra outputs.

In the long term it would be very nice to use the stream of data to do high frequency and highly accurate stepping but this will require quite a rework of the stepper interrupt well we will have to replace it pretty much entirely. The good thing though is that it will be the exact same hardware so once we have something working we can improve it over time.

The i2s peripheral allows for one of the 2 channel to be constant base on a register, therefore we can toggle outputs simply by writing to that register, no need for circular buffers, DMA transactions and interrupts. The only downside is that only one channel contains data so the effective bitrate is half the clock speed but that really shouldn't be an issue.

Current code looks like this and it looks like it's working very well. I'm running into speed limitations with my small logic analyzer now so I can't really tweak the clocks to achieve the maximum speed but I think with the current config it's already fast enough. Why I'm asking is that with this solution the implementation to HAL should be straight forward but we do not free up cpu cycles. I'm I right? I was thinking complete the other way around. The stepper interrupt would just write to that buffer instead of pulling GPIO's.

As we can toggle the stepper pins at more than kHz the limit is in what time resolution we would need. And the time resolution in not an issue. As an example. If we use a GT5 pulley with 20 tooths and microsteps. So what if we "miss" aka linear jitter, a step in the time domain. One micro step is 0, mm that's maximum error at all speeds for all axis! At slower rates this linear jitter will reduce more but still be there.

Conclusion: We are way below the mechanical error in the stepper motor itself. The size of the ring buffer is only a matter when the stepper movement has to interact with other interrupts as when homing and probing. But let us look at the linear jitter again. That sounds like a bad numbers.

Well that was at The ring buffer will be have a round trip of less than 0. My thinking with the ring buffer is that we would not need any semaphores or other task write handlers for that buffer in FreeRTOS. Just do a write as it is a buffer.

Add a new data flag to the function and the ring buffer could loop the same data as long as no new data has arrived. No interrupts just a loop that feeds the DMA with the same data as long as it has not change. And if changed update the ring buffer and keep filling with the latest word. There is a bug in the sample rate settings in ESP32 idf.

It uses an int! This code made my bench test go at a much higher sampling rate:. Just a few questions to clarify. Also, are the outputs from the shift register going to be usable for LCD? What we are trying to do is take the "parallel outputs" thats controlling the steppers, serialize it to a data stream that then is transferred via I2S and converted back to a parallel output again.

If simon-jouet get this working all outputs could be handled so making a parallel interfaced LCD working would work as long that you don't read any data from it. So for the first point yes writing the registers should work from the interrupt, it's just writing to a memory location so there shouldn't be anything special about it. Regarding the CPU cycles there can't be anything that's much more efficient that the way I'm proposing here. It's a single memory write and that's all, the transfer of the data to the shift register is then entirely managed by the I2S peripheral.

Even if you want to use DMA for larger transfer you also need multiple registers to be modified. Yeah that's in line with what I was talking about previously of using the I2S stream to actually queue operations. This approach would significantly reduce the number of interrupts on the ESP32 and might potentially give a higher stepping rate.

The reason why I'm not doing it this way to start with, is that's it's significantly more effort as it requires a very big rewrite of the stepper ISR to actually not be an ISR but just queue the operations in a buffer , Anyway that's clearly something I'm interested in doing at a later point. If you want to see how it could done have a look at the LCD display examples it's very similar, took me some time to understand how the DMA controller works on the ESP32 but I think I'm getting it now : , just hope I will remember when I try to do that!

So the issue here is that the ESP32 idf I2S driver is very much designed to stream audio which is the main purpose of I2S so you give a sample rate and they calculate the prescalers for the clock. In the current code, I've extracted only the necessary from the i2s driver and I set the clock manually. You can look at What state are your code in at the moment?

Would love to try it out. Make a new repro on this and move the further discussions about it to that? Aggebitter Super slow reply! So I worked quite a bit on that over the holidays but I was travelling and on my laptop so the code is mostly in place for an experiment but I haven't tried it yet on hardware. I'm back to work now so I will try this out probably this weekend. Regardless on how the testing goes I will probably create a new branch on my Marlin repo with the code so you can check it out if you are interested.

I will post here once that's done. Not too sure if it works well yet but that's a detail I will push the code soonish. Here is the code! I just pushed a bit more code and I got my first 3D print through the i2s port :. Also at full speed I can't really debug anything at my saleae clone can't follow up, I will have to invest in a scope at some point any suggestions? I'm thinking of a Rigol MSO but the price is a bit steep especially just for hobby work Next step will be to design the R2 board with a better layout and shorten the tracks as much as possible to reduce the noise.

After that I might start looking at replacing the stepper interrupt with an I2S stream through DMA that would be great but probably not straightforward at all. I use one similar to that and the much cheaper Rigol DSE and between the two I can do just about anything I need to plus a good bench supply and multimeter of course short of RF work.

My previous offer still stands - if you'd like me to have something like the DSLogic Plus sent to you so you can continue your work on this I'd be happy to provide that. I'm going to have 5 or 10 printer controller boards made soon for this setup with two shift registers - happy to provide a few of those as well when I do.

And share the files of course. Hi ekettenburg. Thanks, yeah the approach with the MSB set is a bit of a hack but it allows us to keep everything within the ESP32 HAL which is perfect in the short term and is much more likely to get merged into upstream Marlin.

Until someone else gives it a shot I will keep it here and I will open a new MR on Marlin at some point soon to add support for this, the improved ADC which I need to cleanup and maybe few more things. The DSLogic Plus does look very nice indeed and it's reasonably priced. For this work it should be good enough.

Thanks for the offer and I might take you on it - just that asking for stuff when I just do that as a hobby somehow doesn't feel right :. For the printer controller board, I'm revising the R2 but if you are planning to get one sorted too it might be worth splitting resources so we don't end up with many different but similar boards and each time we need to revise the hardware we are all having to redesign it.

Plus having less hardware design on my end will give me more time to focus on the software :D. I started modifying the schematic for the R2 and I will push that soon. Just as an FYI I would recommend sticking 4 shift registers and not 2 for a few reasons:.

I was really excited to see the motor control. Can I ask if you think this will work for PWM too? I am also interested to incorporate 74HCs into the board I am working on right now. But first, I need to get the current version to work. That's why we only plan to have two shift registers - it meets our needs.

That said I will make an easy way to add two more as no doubt 4 is better than 2 for hobbyist use or for power users if we end up putting it into a printer. Have you pushed the improved ADC code anywhere? I'm interested to see how you've approached that. I've tested a few different approaches from general calibration formulas to reading the calibration value on newer chips to manual calibration - all have worked "well enough" but the later of course isn't usable for production boards.

It kind of depend how the shift registers are used. Like i mentionned in my previous message, in the long run my goal is to use the ESP32's DMA to actually queue stepper operation. What I have in mind is if 4 shift registers are used is to use the first two with DMA control so it's very fast and very accurate but computed beforehand and use the other 2 as a GPIO expander so we can actually control more outputs using the static channel system that I'm using now.

If you use the right mosfets you shouldn't need to feed them 5V quite a few mosfets can have a very low Ron even with a 3. With a few more people working on software and hardware I think we can end up with a very very nice system :. I haven't pushed the ADC code anywhere just yet, it's quite nasty at the moment but I can post a diff at some point when i'm on the machine with the code. My current approach includes a few workarounds but the result is quite satisfactory except at low temps below 30degrees but I don't care much about that for now.

Using this approach I've been able to measure the temperature between 30 and upper bound on the thermistor table I use. Just love it! This has been a enervating thought that has been on my mind for some years now. I was really annoyed that every one was talking about stepper speeds, better arc tolerances and so on but no one did some thinking tolerances we actually have in the mechanics and by taking that into account write the software that does not have a lower value fault than the mechanics.

Is there a way to get one of your R2 prototype boards when you have the design ready? As an hobbyist army employee both time and finances are mostly going to the family ;- Will of course pay for the making and postage. Aggebitter sorry for the slow reply! For the time being I'm stepping a bit off in designing the R2 prototype as both vivian-ng and ekettenburg are working on one, I think it's better for me to focus on the software.

I've just pushed a new branch espi2s-dma that adds support for proper step scheduling over I2s using the DMA controller and removing the constant calls to the stepper isr. I think this will provide a huge performance boost!

Anyway I'm super happy with the result, just finished my first print using that. The next step might be to stop using bresenham and schedule each step independently but my lack of knowledge in the current code will probably make this a bit tricky :.

At this point there won't be any more long interrupts and we can start playing a bit with the ESP32's capabilities :. This also makes a lot off "standard" extensions as display, PWM and servo control a possibility. Hi, great job! I was thinking if the esp32 needs more gpIos for normal stuff couldn't you use mcp23s17 spi or mcp i2c?

Thanks for all hard work you all are doing! Aggebitter yeah the mapping needs to be redefined as it also opens up the second SPI port which could potentially be useful especially for debugging as it's the same as the JTAG port. I think ejtagle is working on support for the ILI tft displays, I haven't seen any code for that just yet but when something is available I will have a look, it would be a nice addition. Regarding the 32 outputs ports I think there might be some limitation on what they can be used for especially if we use the DMA channel to control them but I think in most cases it will work just not sure for things like CS lines for TMCs.

I was thinking last night that it might be possible use i2s for inputs too, and therefore have 32 outputs and 32 inputs both at the same frequency. I might have a look when I get some free time. I would not use any I2C extender for endstops as they are as time resolution critical as the stepper movements. So endstops should be interrupt driven.

The problem with that is mostly the latency, if we use DMA to control the steppers then we will start filling it with data as soon as it's empty. For some stuff it doesn't really matter, but for the CS lines it will probably be an issue because we will have to wait that long before the ESP can start doing the transfers. Like misan said most GPIO expanders have an interrupt line so the steppers can be paused until we figure out what caused the interrupt.

From the i2s driver in the esp-idf and the TRM it does look like it, the sample rate for the input will be far too fast as fast as the output but we can just ignore some samples. I should get some 74HC soon to test that out. I think it's less important to get that working than the steppers but it might be good to have nonetheless. The datasheet gives the number of usec for interrupt latency not sure if too high.

The SX looks to have much better timing characteristics. But even us shouldn't be much an issue I think, I should double check but with a normal homing rate that might be max a step or two. Hey simon-jouet ,. First of all - great work! Amazing how ESP32 board community is evolving and old Arduinos are being replaced recently. I wanted to ask if R2 board on your branch already have these changes related to new shift-registers?

Is it ready for prototyping and testing? Hi kkszysiu ,. Thanks, glad people are starting to use it, shows that the many days spend in the soft and hardware are finally being worthwhile. Yeah the R2 branch has been updated last weekend iirc with more fixes and Tweaks and it contains the shift registers for the i2s stream.

The only step left is to do the pcb design, got some feedback from a friend but I find pcb routing very painful so I haven't worked on it much yet I do not know how valid it is, I'm a pretty newbie in case of hardware. Trying to get more experience thanks to projects as this one :. I think i2s stream is a brilliant idea, and really the way to go - to get the hands on some testboards i've made the routing from PR 6 without major modifications in the schematic. Should be pretty valid - if you have the parts.

Is the pin-mapping already fixed? Shuffling the shift-register pins and splitting J6 could reduce some pressure from the routing. Ringel Just ordered some PCB of your design and will test it out on my holiday. The 5V tolerance, shift registers X,Y,Z,E0,E1 , voltage dividing the analog input and adding a mosfet driver for heater mosfets and we have a direct Arduino Mega replacement.

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Forex sell dollar Love it! If the above inverters have Schmitt inputs, each would be doing it's little part in making that logic change faster. Little things can make a big difference and it takes time to learn them. It may be worth biting the bullet and investing in one controller per track segment and getting rid of the controller to track segment switching relays. I have used this approach in a number of commercial products over the years and have been able to support large numbers of key inputs without consuming a high percentage of the processing bandwidth if the MCU. Add a comment.
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Investment advisers act section 206 Vertical rows columns are motor controller Using the relays you can increase the rows. To make it easily configurable, maybe a define statement should non investing buffer 74hc165 used. But even us shouldn't be much an issue I think, I should double check but with a normal homing rate that might be max a step or two All reactions. You could control inputs of motor controller using logic. The following users thanked this post: ilium Hi ekettenburg Thanks, yeah the approach with the MSB set is a bit of a hack but it allows us to keep everything within the ESP32 HAL which is perfect in the short term and is much more likely to get merged into upstream Marlin.
Forexlive adam button Meanwhile, I have zero understanding of stepper. If i've missed anything let me know :. I guess on the esp example that's why they continuously send the same data, so Value investing reddit gone need to look into that either to keep queuing data, make the buffer cyclic so it resend the same data over and over again or be able to switch off the clocks when the buffer is empty. Each type of switch and application will have its own set of unique requirements. Hot Network Questions. I would use Molex 77 connectors as the inter-connect current would be well under their rated 4. There are lots of circuits around for debouncing switches; this is considered one of the best: For more information, see " A Guide to Debouncing ".
Non investing buffer 74hc165 Can I ask if you think this will work for PWM too? The firmware can still use timer interrupts internally to just feed the DMA and by doing so we will free up here lot of cpu cycles. I'm back to work now so I will try this out probably this weekend. If you draw the clock signal the inverter input or buffer on paper and then make a copy on a transparency. It uses an int! I am learning so much through this project, thank you again for all your help.
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Operar intradia forex converter If all key-bounce events happen quickly, there is source harm in feeding the key switches directly to the shift registers non investing buffer 74hc165 letting software take care of them. Aggebitter Well done with that, I'm looking into getting the I2s peripheral to behave like I want at the moment. The first board I made quite a while ago before this was for ramps, the problem is that there is so much difference in pin capabilities that half your RAMPs pins won't be connected to anything. I'm not sure how much heat will be generated by a linear regulator dropping 12v to 5v and sinking the mA per board. I should get some 74HC soon to test that out.
Non investing buffer 74hc165 If you want to see how it could done have a look at the LCD display examples it's very similar, took me some time to understand how the DMA controller works on the ESP32 but I think I'm getting it now :just hope I will remember when I try to do that! Just hate spell checking All reactions. Hot Network Questions. If they have silver or other metal contacts, decrease R6 to 1K t get at least a few mA wetting current. It uses an int! Shuffling the shift-register pins and splitting J6 could link some pressure from the routing.

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As for atoi , have you read the Codevision help? I'd suggest you go away and do some research. It might give us some time to recover from the annoyance you've caused. I'm used to the one in av-gcc. The version of itoa in Codevision does not offer this choice and only does decimal so it has two parameters. They are the same as the first two in my examples. It seems you are just putting fragments of code anywhere without regard to what each line is doing or trying to accomplish.

Skip to main content. Log in or register to post comments. Go To Last Post. Level: Wannabe. Posts: 79 View posts. Posted by spassig : Fri. Mar 10, - PM. Fivestar widget 1 2 3 4 5. QH of the second connected to the SER of the first. Each parallel input has a pullup resistor, so buttons connect to ground. Hence, if nothing happens, I should read 10 1's and 6 0's. I read 0x04 from both '!!! No button press is detected I am not deboucing, I just keep the button pressed for seconds Connections are good, checked them like ten times.

This topic has a solution. Jump to the solution. Last Edited: Sat. Mar 11, - AM. Level: Hangaround. Posts: View posts. Posted by balisong42 : Fri. Log in or register to post comments Top. This reply has been marked as the solution. Posted by Kartman : Sat. Posted by spassig : Sat. Mar 11, - AM Reply to 3. Kartman wrote: This should hopefully work a bit better - I've not tested it. Mar 11, - PM. Posted by azizollah : Tue. Mar 14, - AM. Level: Moderator. Location: using avr-gcc in Finchingfield, Essex, England.

Posted by clawson : Tue. Posted by Kartman : Tue. Mar 14, - PM. Last Edited: Tue. Posted by theusch : Tue. You can put lipstick on a pig, but it is still a pig. I've never met a pig I didn't like, as long as you have some salt and pepper. Posted by spassig : Tue. Posted by azizollah : Wed. Mar 15, - AM. Posted by awneil : Wed. Mar 15, - AM Reply to Posted by spassig : Wed.

Remember: is parallel-in-serial-out PISO. So you can't feed the with a serial data, it won't work. As well, you can't feed the with parallel data. Then, I am still confused how many bits you need to read and write. If you need to read 16 bits you need to have two Same for They need to be daisychained, and signals need to go to both of them. In fact I have the LCD and can send it to. I will try what you said. Posted by valusoft : Wed.

Last Edited: Wed. Mar 15, - PM. Dear Kartman, I checked input and output ,the result is : whatever the input ,the out put is always the same! Level: Raving Lunatic. Mar 15, - PM Reply to Posted by azizollah : Thu. Mar 16, - AM. Posted by clawson : Thu. Mar 16, - AM Reply to Last Edited: Thu.

Posted by awneil : Thu. Posted by azizollah : Sat. Mar 18, - AM. Once it is all wired up you can move forward and write some code to make it all work. One way is to use the SPI bus, which would allow you to make use of existing libraries to simplify writing code. This is the method we will employ to work with the 74HC shift register. Arduino provides a shiftOut function to simplify moving data on a serial connection.

It can take a byte value and output it in a serial format in sync with a clock pulse on another pin. You can choose to output the data in two directions. Our sketch is pretty simple. The shiftOut function takes care of sending our data to the shift register and of creating a clock signal.

This sketch is just an adaptation of one that Arduino provides in their excellent lesson on using the 74HC with the Arduino. It uses the eight LEDs as the display for a binary counter. We begin by assigning variable names to the pins connected to the 74HC All of these pins are then set up as outputs. We then move on to the Loop. We use a for-next loop to count from 0 to , incrementing by one.

On each increment, we write the counter value out to the shift register. The result is that the LEDs display a binary count from 0 to You can experiment with the code and manipulate some values and observe the effect on the LEDs. In some displays, this may be substituted with a colon.

Both display types use the same pinout, so it is very important to know what type you have. When connected with the proper polarity it can be used to light the LED elements. The Common Cathode display is more common and is the type we will be using for our experiment. So we can use the exact same circuit to hook it up. Use the chart in the hookup diagram to connect the display pins to the dropping resistors.

Note that the display will have two COM pins, you only need to connect one. Once you have that all hooked up you can test it by running the previous sketch, which should test all the LED segments including the decimal point. But to actually display something coherent we will need a different sketch.

Here is the sketch we will use to test out our 7-segment display. We start again by defining our connections to the 74HC Then we create an array with 16 elements, each one representing the pattern for a character to display on the 7-segment LED. The elements are written in binary and it makes it simple to understand how they work.

Within the binary byte, each bit represents one of the LED segments. Once again in Setup, we set our connections as outputs and then move onto the Loop. Again we use a counter, only this time ist is between 0 and We will display these values as they are counted on the LED display in Hexadecimal format. We step through the array one element at a time, using shiftOut to send the element data to the shift register.

Load up the code and observe the display. For that job, we will use the 74HC We will use the 74HC shift register along with eight momentary-contact pushbutton switches. The shift register will take the 8 inputs from the switch and send them to the Arduino as serial data. Once again Arduino has a dedicated function for receiving serial data.

The shiftIn function shifts serial data in one byte at a time. As with its cousin the shiftOut function the shiftIn function also supplies a clock signal to synchronize the data transmission. The inputs of the 74HC need to be pulled down LOW to prevent false readings, so in addition to our eight pushbutton switches we will also need eight pulldown resistors. I used 10k resistors, but any value from 4. Once again I used a uf decoupling capacitor, make sure you observe the polarity when connecting this.

Once you have it all hooked up we can focus on the sketch we will be using to make this work. Our sketch is very simple, as all it does is read the status of the pushbuttons and display the results on the serial monitor. The sketch starts out like all of our previous sketches, defining the four connections to the IC.

In the Setup, we initialize the serial monitor and then set the connections up as required. In the Loop, we first write a pulse to the load pin, which will have it load the data from its parallel input into a buffer to be worked on.

We finish by taking the clock pin HIGH, signifying we are done. Load the sketch, open your serial monitor and observe the output. The data is all held HIGH on the output, the opposite of what is wired on the board. Pressing a pushbutton will cause it to read LOW, even though that is the opposite of what is really happening. This is because we are using the complementary output from the 74HC Our data is inverted.

Keep on reading! The example we just used has many practical applications, one of the obvious ones is as a keypad although there are better ways to make a large keypad. For a project that requires a lot of switches, it is a useful design technique. One great application of this circuit is to use it with DIP switches or jumpers, ones that are only occasionally set.

You can use the 74NC to reduce the number of connections required to read an 8-position DIP switch, and just read it in the Setup routine so it is only read when the device is powered on or reset. Of course, it would be a shame to have wired up all of those LEDs and switches without going the extra step to connect them together!

If you built each of the demonstrations on its own solderless breadboard as I did then hooking both of them together is very simple. Leave the connections on the breadboard so that you can reconnect them to the other Arduino. You can connect the 5-volt and Ground connections to the other breadboards power rails. When you are done try running the previous sketches on the Arduino, everything should still work. As our demo is essentially two demos fused together our sketch is pretty well the same thing.

The purpose of the sketch is to simply use the LEDs to display the status of the pushbuttons. Really boring, and a complete waste of a microcontroller and some shift registers, but as a demonstration, it works well. We stare by once again defining pin connections to both integrated circuits. And in the Setup, we initialize the serial monitor and set the connections up as required.

The Loop starts with the same routine we used earlier to read the pushbutton values from the 74HC Next, we use the same code we used earlier to write the data to the 74HC But we make one change to the date we send to the shift register.

Remember, our data from the switch is inverted. If we send it to the 74HC it will work, but the LEDs will all be on, except where we have pressed a pushbutton. The tilde squiggly symbol inverts the binary data, turning every zero into a one and vice versa. Exactly what we need to do. This matches how we receive it from the pushbuttons.

As we have eight switches we can select eight patterns. Then we have eight cases, one for each switch press. You could probably add more if you wanted to allow for pressing two buttons simultaneously, but eight was enough for me! In each case section, we populate the datArray array with LED patterns, written in binary so they are easy to see. I used eight elements in the array to make it easier, but you can increase this to any number you like. Just change the number in the array definition and in the for-next loop that cycles through the array elements.

I set the delay between pattern changes to ms, but you can change that. Even better, try putting the delay as a variable in each case evaluation, so you can make the patterns run at different speeds. You could also make the speed variable by adding a potentiometer to one of the analog inputs and using it to set the delay time.

Shift registers may be elementary building blocks that might seem out of place aside microcontrollers and other more capable chips, but they still can perform important functions in a modern design. They can be very useful if you need to add extra inputs or outputs to your project, they are inexpensive and easy to use. Comments about this article are encouraged and appreciated. However, due to the large volume of comments that I receive, it may not be possible for me to answer you directly here on the website.

You are much more likely to get answers to technical questions by making a post on the DroneBot Workshop Forum. Your post will be seen not only by myself, but by a large group of tech enthusiasts who can quickly answer your question. You may also add code samples, images and videos to your forum posts.

Having said that, please feel free to leave constructive comments here. Your input is always welcome. Please note that all comments may be held for moderation. Bumping this up in case the author is checking comments. Would like the link as well. I found this on Mouser. Hello, Thanks for the great content. There was a small error in the 7- segment display hookup. Great tutorial, 74HC works like a charm.

Just to let you know that after seeing this I am combining a the two chips to aid in Reprogramming a AT28C 15PI Using these two chips allows me to write and also over come the issue of getting the WE pluse time down to ns using a NPN transistor. Which Ben Eater showed when programming a 8 bit computer.

By using these chips so much more can be accomplished. Including a robotic car using old but … Read more ». This is a fantastic guide, thank you. Hy,Im using 74HC but when pressing button it doesnt returns the change in state it always return