Multiplexing high-current, high-voltage 7-segment - Page 1
Forum section: electronics / beginners

author: Peabody
author_rank: Super Contributor
timestamp: September 30, 2024, 04:25:26 pm
content: I'm participating in a thread over on the Arduino forum, but I'm just a hobbyist, and need some expert advice from the EEs here. The OP wants to build a display of up to 11 digits of what I assume are large 7-segments. I don't have a link, but he describes them as CC having Vf = 7.8V, Imax = 60mA. The special requirement is that the display has to show up properly on video as well as in still pictures. Ouch.Originally he planned to have continuous drive, with one high-current, high-voltage 595 equivalent on each digit. But those steroidal 595s are expensive, and I wondered if it would be possible to multiplex the display using one such suped-up 595 driving all the digits in common, and two similar chips sinking the 11 common cathodes one at a time.I've worked out software that runs a timer interrupt at 100us, and for a Nano or Uno at 16MHz it takes up about 1/3 of the time in servicing the interrupts. I've tried it with a normal digit, and pictures taken at 1/1000 sec look pretty good. But what concerns me is whether it's reasonable to be switching maybe 50mA at 10V or so at a speed of 10KHz over a distance of something in excess of one foot. Actually, it's a bit worse than that because during the ISR, current is shut down while the changes are taking place so as to prevent ghosting. So in the case of two adjacent digits both having the same segment turned on, current would be switched off, then back on, over just a few microseconds.I've never done anything like this, and just don't have a feel for whether it is at all reasonable. It may be that 11 digits with this much current and voltage, at this distance, is just a bridge too far for multiplex. Any opinions would be appreciated. Is it "no problem", or "no chance"?

author: Andy Chee
author_rank: Super Contributor
timestamp: September 30, 2024, 04:34:18 pm
content: As long as the average current remains within spec, LEDs can generally take a fair amount of punishment when being pulsed with high currents.As for the 595 driver, you will have to buffer it with something like the ULN2003.

author: MathWizard
author_rank: Super Contributor
timestamp: September 30, 2024, 05:21:48 pm
content: What about just making some higher voltage BJT drivers for the LED's ? Just some 2N2222/2N3904/BC547, anything like those would be plenty fast for switching LED's up to the kiloHertz or whatever you would need to be picked up by a camera.

author: pqass
author_rank: Super Contributor
timestamp: September 30, 2024, 08:19:42 pm
content: 10KHz?You only need 60Hz per digit, so an 11 digit multiplex is 660Hz, or an interrupt every 1.5ms.However, you should probably make it an odd rate like, say, 83Hz per digit or 913Hz total, or an interrupt every 1.1ms.That way it won't coincide with any standard shutter rate.ISR-time should be minimized; just be sending out the display buffer and not execute complex calculations.I've successfully multiplexed 16 digits; sending out one byte via SPI every ISR call (1600Hz, or every 625us).The common cathodes were driven from two ULN2803s via two cascaded CD4017 counters.The cascade arrangement was such the Q1..Q8 of each counter enabled a single cathode in sequence.The first counter would stop at Q9. The second counter would count only after the first was stopped then reset both at its Q9.Q0 of the first counter would signal the MCU via MISO when the count was just before the first digit (to re-synchronize if necessary).The counter clocks were driven from the MCU device select/reg. load pin for the '595 (low-high-low on RCLK).

author: Peabody
author_rank: Super Contributor
timestamp: September 30, 2024, 09:43:15 pm
content: Thanks very much for all the comments.We're looking at the MIC5891 for the anodes. That's a 595-type shift register, which handles much higher voltage and current. Its outputs are open emitter darlingtons, so I was hoping there would be no need for a ULN2003. And besides, I thought the ULN2003 could only sink - it has a common emitter and open collectors. His displays are common cathode, so we need to source high current into the individual segments. I don't know of a cheap 7-gate darlington array with open emitters.Then he already has the TPIC6C595 on hand, which would be on the low side, with one input connected to the CC output of each digit. He would need two of them to handle 11 digits.QuoteI don't know what it's for, but I have the same question about brightness. But these days LEDs are so efficient that it might work. However, it might be possible to split up the digits into 6 and 5, and drive each half with its own MIC5891. The two TPIC6C595's would still be enough since there are still only 11 digits. That would effectively double the brightness on the same current since each segment would be lit for twice as long. So it would be 60/6 = 10mA average current. But that's still better than 11 MIC5891's at $3 a piece.QuoteI don't think there is a problem generating the current. The MIC5891 has darlington outputs, which should be good enough. What I was concerned about was switching the current at 10KHz - I don't know what could go wrong doing that - reflections, or spikes, or whatever things professionals know to watch out for, but hobbyists like me don't.QuoteFor video, perhaps, but still pictures are the complication. What if the shutter speed is 1/1000 sec? This requirement is the biggest obstacle to this working easily, but he was pretty clear about needing it, and it's why he was planning to make it continuous. I was just hoping there was a better way using multiplexing.Well, I'm still not clear about whether switching the currents will cause problems. I know that as lines get longer the frequency that can be supported reduces. And presumably the same as currents get bigger. I just don't know at what point that starts to be a practical problem. I mean, 10KHz is not exactly RF.

author: amyk
author_rank: Super Contributor
timestamp: September 30, 2024, 10:15:36 pm
content: Quote from: Peabody on September 30, 2024, 04:25:26 pmAre these LEDs or incandescent bulbs? LEDs react near instantaneously to current.

author: Peabody
author_rank: Super Contributor
timestamp: September 30, 2024, 10:17:15 pm
content: Quote from: amyk on September 30, 2024, 10:15:36 pmThey are 7-segment LED displays. Just bigger than normal.

author: Benta
author_rank: Super Contributor
timestamp: September 30, 2024, 10:19:18 pm
content: What is the supply voltage? And is it stable and fixed/defined?

author: Peabody
author_rank: Super Contributor
timestamp: September 30, 2024, 10:47:41 pm
content: Quote from: Benta on September 30, 2024, 10:19:18 pmI don't know. Of course something greater than 7.8V, but I don't know what he will be using.

author: pqass
author_rank: Super Contributor
timestamp: September 30, 2024, 10:51:42 pm
content: If you're multiplexing then you would only need one MIC5891 (like anodes across all 7-seg displays; all a-segs connected, all b-segs, ... g-segs, dp-segs) and two ULN2003+74xx595 or two TPIC6C595 where each output drives one display's common cathode. And every ISR call, you'd be sending 3 bytes. However, the TPIC6C595 has a max of 100mA per output yet each display segment can be 60mA? The ULN2003 can support up to 500mA per output (which is >8segs*60mA/seg).For 1/1000s stills you'd have to drive all segments full-time. This can bepossible, cheaply,if you employ a common VFD display circuit design; discrete PNP or PFET per segment driven by a '595 output (times 11 displays) but with a negative common cathode. See attached (simulationhere).

author: Peabody
author_rank: Super Contributor
timestamp: October 01, 2024, 04:55:45 am
content: Quote from: pqass on September 30, 2024, 10:51:42 pmExactly.QuoteWell, he would be sending one full byte to the MIC5891, but on the cathode side he only has to shift one bit on each interrupt. So the On bit would move across the register, activating one display at a time. The latch would be permanently On. So he would just toggle the serial clock pin, and serial data would always be low except when it rolls around to the first digit.QuoteI don't read the datsheet that way. 100mA is the continuous current limit per output. I think the 250mA is a pulse current limit per output. Now of course 250mA isn't 420mA, so the TPIC6B595 would be a better choice. But he already has the 6C, and they might work ok if there aren't too many "8" and "0" values. But in the worst case, I think he could double up the 6Cs, even soldering two of them together piggyback.QuoteI think you're probably right about the 1/1000s stills, but it might be worth just trying it out on one digit that's turned on 1/11th of the time. It probably won't be bright enough, but I think it's worth a try. Attached is such a 1/1000s picture that looks ok, but that's using my super-efficient red display, not whatever he's using. But it also used 220R resistors, so it could have been brighter.

author: BennoG
author_rank: Frequent Contributor
timestamp: October 01, 2024, 05:18:53 am
content: I would skip multiplexing.Modern film/photo camera have shutter times in the 1/10000 s (on a sunny day), so if you want do do multiplexing and don't see it on the camera you need to multiplex (every segment at least 1 time on) at least 50kHz.Benno

author: pqass
author_rank: Super Contributor
timestamp: October 01, 2024, 05:29:46 am
content: QuoteIt doesn't work that way. RCK only works on the rising edge (see description8.3.1 on page 12).It's not a transparent latch like C on the'373.

author: Peabody
author_rank: Super Contributor
timestamp: October 01, 2024, 01:43:09 pm
content: Quote from: pqass on October 01, 2024, 05:29:46 amYou're right. I was looking at the MIC5891, which is level triggered, and just assumed it was the same. So I would toggle the serial clock once, then toggle the latch clock.

author: mikerj
author_rank: Super Contributor
timestamp: October 01, 2024, 02:06:14 pm
content: A boat load of shift registers and transistors seems like the lowest cost solution without resorting to very high speed multiplexing. This will also take negligible CPU time, just load a buffer up with the next display data and let the SPI peripheral squirt it out, just once very fast interrupt per byte.The TLC6C598 will directly drive LEDs up to 50mA and even in 10s quantity is quite reasonably priced ~$0.60

author: Peabody
author_rank: Super Contributor
timestamp: October 01, 2024, 04:46:00 pm
content: Quote from: mikerj on October 01, 2024, 02:06:14 pmWell, again, the TLC6C598 is open drain. It won't work with his common cathode display. He would need something similar, but which can source current into the segment anodes. The MIC5891 was all I could find that does that at 9V, but it's not cheap.

author: Benta
author_rank: Super Contributor
timestamp: October 01, 2024, 11:14:36 pm
content: CC 7-segment displays are always a pain with a lot of level shifting involved. Best would be to switch to a CA type instead.If not possible, here's a completely different approach:A floating "HV" display supply that will have its positive voltage referenced to the controller's positive voltage. That will bring all output switching and current control for the LEDs into the low-voltage realm of the controller.The cathode voltage will be "dangling" down there somewhere, but who cares? all the rest is 3.3 or 5.0 V circuitry.This is what I mean:(Nice is that it's constant-currnet drive at 25...30 mA per segment)

author: Peabody
author_rank: Super Contributor
timestamp: October 02, 2024, 01:07:03 am
content: Yes, @pqass also proposed that method in reply #9. I'll pass that along.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 02, 2024, 01:31:27 am
content: Well, switching on and off depends on the speed of the drivers doing it, and ringing depends on the impedance of the route.60mA isn't extreme; the peak current from a 5V CMOS logic chip into a 70 ohm trace is ~30mA. The voltage here is higher, and the current is higher; in EM terms, it's basically the same.Microseconds aren't important: for feet of wire, you're looking at whole nanoseconds; a bit more including LED and driver capacitances. Microseconds are basically DC, handled in the nearby bypass cap (or even a fairly distant one).As a general rule, only use what bandwidth you need. This might not be optimal, as you're starting with the risetime of the Arduino, and the driver IC(s), and so filtering would be needed -- a tedious parts cost. Otherwise, construct it with good enough signal quality and shielding to behave: ground plane most important of all, perhaps source termination resistors and/or ferrite beads on longer signals, etc..The same applies to the (3.3/5V?) SPI signals, if using shift registers; or even just GPIOs really. Newer AVRs, and most(?) anything ARM, have drive strength or slew rate control which can help ease things, and source termination is about all you need for signal quality on CMOS lines (small capacitance load at far end). SPI ran over long cables should be shielded, keep the shield connection short and well connected to ground plane.Tim

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 02, 2024, 01:32:49 am
content: Grab any generic PNP transistor for each anode.Most logic won't handle 7V, use a ul2003 or a bunch of NPNs to drive them.

author: Psi
author_rank: Super Contributor
timestamp: October 02, 2024, 01:41:10 am
content: Quote from: BennoG on October 01, 2024, 05:18:53 am+1 for this.If it has to look good on video drive each segment with DC only.This obviously means you cant use matrix LEDs but normally 7 segments are just common'ed, so totally fine to drive with DC from a latched shift register or something

author: ArdWar
author_rank: Frequent Contributor
timestamp: October 02, 2024, 02:16:13 am
content: You can try TBD62783 for the high side switch and drive it with normal 595. No need for additional rail.Otherwise, yeah, bunch of discrete transistors is probably still the cheapest option here. Sourcing (high side) driver is so uncommon that any monolithic solution will be at a premium.

author: Peabody
author_rank: Super Contributor
timestamp: October 02, 2024, 04:48:43 pm
content: Quote from: T3sl4co1l on October 02, 2024, 01:31:27 amThanks very much for the reply. Looking at the continuous option first, since an HV 595 would be right next to each digit, and the cathodes will be grounded, there shouldn't be any problem with the load lines. But the Uno would be directly driving the SPI lines, and the serial clock in particular would be fanned out to each of the 11 chips, at varying distances. I've seen schematics of button boards and such where this is done, but don't know if it actually works. Serial data would only go to the first chip, and is then refreshed going to the next chip in the cascade. But I guess if the clock line is a problem, a single-gate buffer of some kind could solve that.In the multiplex option the SPI lines would be quite short, and only going to one chip. But the load current lines would fan out over some distance. I figured out a way to avoid having to power down those lines during changes (to avoid ghosting) by triggering all the latch pins from a single GPIO pin so both the anodes and cathodes change state at the same instant. That means that if the refresh period is 100us, that's the maximum speed at which the load lines would change state. If I understand what you've said, that's not likely to cause a problem so long as the layout done properly.QuoteSorry, you've lost me.QuoteIn multiplexing, the SPI transfer would be initiated toward the end of the timer ISR, and only needs to complete before the next interrupt. The slowest you can run SPI on the Uno is at 1/128th the speed of the 16MHz system clock, which would be 125KHz. I think the ISR will be fairly short, so that should work timing-wise. I just don't know how good the GPIOs would be in driving these lines.

author: Peabody
author_rank: Super Contributor
timestamp: October 02, 2024, 05:01:26 pm
content: Quote from: Psi on October 02, 2024, 01:41:10 amIt seems to me that video is the lesser problem. The frame rate will likely be either 30fps or 60fps, and if multiplexing is fast enough that should be doable. But stills is another matter, particularly if shooting outside.I'm finishing up some test code that he can run with one digit to test brightness and photogenicity.Edit: One thing I haven't considered is the effect of rolling shutter in CMOS sensors. I don't know if that makes things better or worse.

author: Peabody
author_rank: Super Contributor
timestamp: October 02, 2024, 05:07:14 pm
content: Quote from: ArdWar on October 02, 2024, 02:16:13 amThanks very much for that find.QuoteYes, that appears to be the case. A good reason to use common anode displays I guess.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 02, 2024, 06:20:48 pm
content: Quote from: Peabody on October 02, 2024, 04:48:43 pmThat's normal, CMOS fanout is quite large. If there's a lot of distance (delay) between chips, you can end up with indeterminate or ringing clock waveforms and get inconsistent and lost data (multiple shifts per edge). This is due to the characteristic of a source-terminated transmission line, that the voltage level on the line, at a middle position, is Vstep/2 after the incident wave, until the reflected wave passes.If everything fits on a breadboard like pictured, it's likely that delay is less than the risetime, and the clock will be well-behaved.QuoteYou'll still get a faintly visible ghost image, actually. The load switches won't turn on/off at exactly the same time, plus the one column's capacitance has to discharge through the newly activated rows (or, even if there's a pulldown resistor to discharge it, some charge will take the LED route). Probably nothing that would be visible daytime, but indoors or dim conditions perhaps.But yeah, nothing wrong with that at all.QuoteBandwidth is not just the clock rate, but the edge rate too. You might only be toggling columns at some kHz, but the MCU or driver's risetime might be a few ns, thus the bandwidth extends into the low 100s of MHz. You need a scope of at least as much bandwidth to properly resolve the risetime of such a signal, and you need a medium of such bandwidth to transport it (bandwidth, usually in terms of attenuation per distance vs. frequency, is a characteristic of a real transmission line).Filtering components can be added to slow that down (give or take clock pin specs -- in the extreme case, a schmitt trigger might be needed to honor maximum risetime spec), and thus avoid activating any signal quality and EMI issues in the corresponding frequency bands: can't be an EMI problem if you aren't operating in that frequency range to begin with. Conversely, filtering makes your circuit more immune to interference in the cutoff range.QuoteI mean, they're made to do it. And a heck of a lot faster than that; GPIOs typically have a toggle rate equal to peripheral clock (which is trivial on ATMEGA, but most ARMs for example, the CPU can run much faster than the peripherals).Average HC/LV family CMOS pins (and by association, most CMOS ASICs -- but not guaranteed, always check the datasheet!) have a source resistance of 30-70 ohms (depending on type, supply voltage, temperature, manufacturing variation, and polarity -- pull-up (PMOS) is usually weaker), typical trace/cable impedances are 40-120 ohms, so a direct connection, or with a small source termination resistor taking up the remainder (typ. 15-47 ohm), achieves a source termination condition, and good signal quality will be had at the far end of the transmission line.Note datasheets don't spec pin resistance per se, let alone the output V(I) curve; you have to infer it from the VOH/IOH and -L parameters, which are usually given as worst-case, and the average case might be 2-3x better than that.MCU GPIOs can be stronger; they may be made to drive LEDs or other loads directly, i.e. spec'd for 20mA output, or even more, at low voltage drop; again, check the datasheet. That's simply solved by choosing an appropriate source termination resistor.Mind, I'm just going off the cuff here, responding to comments as they come. If this isn't making sense, you might want to raise some more pointed questions -- what is a transmission line, signal quality, etc.? Have you done reflection (ladder/lattice) diagrams before, do you understand how reflections propagate on a TL? Do you know about logic pin equivalent circuits, and how they interact with TLs?Tim

author: LinuxHata
author_rank: Frequent Contributor
timestamp: October 02, 2024, 08:43:47 pm
content: There are dedicated chips used in LED matrix display panels with higher voltage, higher current, anti-ghosting, built in memory and so on.Check Macroblock MBI5026 datasheet as a starting point.

author: Peabody
author_rank: Super Contributor
timestamp: October 02, 2024, 10:36:16 pm
content: QuoteI should have said that under the multiplex option each load line will have a series resistor that will be used to set the current. Does that make things worse, or better?QuoteNo, I'm just a hobbyist. I don't know what any of that stuff is. What I know about transmission lines is that if I make them short enough, I don't have to worry about them. But I don't know what happens if you make them long, other than things I've read about reflections, ringing, overshoots, or whatever. So as a result, I don't have a "feel" for whether this wide-area multiplex system will work at all. Which is why I posted.On another idea, I think it would be possible to divide the 11 digits into groups of 6 and 5, and multiplex both groups simultaneously. A second MIC5891 would be needed, but no additional TPIC6C595s. And seven more resistors. :-)At the end of each servicing interrupt the Uno would initiate sending the first of two bytes, one for each 5891 in sequence. At the end of the first byte transmission, SPI would generate an interrupt, at which point the second byte transmission would be intiated. That would require a faster SPI rate, like fSYS/32 = 500KHz. so that the two bytes are in place before the next interrupt occurs, at which point the latch on both chips will be toggled.Then on the cathode side I already had two TPICs grounding one CC at a time by shifting one On bit through the chips. All I would have to change is to shift through two On bits, 6 bits apart.There is one issue with the TPIC6C595, and that's it's low current spec per line. The 6B would have been better. Anyway, I could add a third TPIC, which would then provide enough pins to have two per digit, for double the current. Then I would just shift through two pairs of adjacent On bits, 12 bits apart.That option would essentially double the brightness on the same current per segment.

author: Benta
author_rank: Super Contributor
timestamp: October 02, 2024, 10:54:23 pm
content: I turned this one over in my mind once more. I'm talking about static drive here.Before seeking out exotic drivers (eg, the TD62783, which is obsolete), why not keep it simple and break away from "everything connects to ground".Why not justfloatthe LED/power stage?That would keep the controller (Arduino?) safe, and solve a lot of other problems.Here's a suggestion using one (cheap) PNP transistor plus one resistor per segment. Current-controlled at 25...30 mA.Each digit is controlled by a 74HC595.The digits are SPI-wise series connected as 11 digits = 11 x 8-bits.The whole shebang is powered from some source that's free to choose, eg, a 15 V PSU or a laptop 19 V supply that's available from the dumpster.The only thing you need to watch out for is the power dissipation in the PNP transistors.I don't see how it can be done much simpler and cheaper.

author: Peabody
author_rank: Super Contributor
timestamp: October 03, 2024, 12:18:52 am
content: I agree that connecting everything to V+ instead of ground makes a lot of sense for the static continuous drive. But he has 11 digits, so that's 77 transistors. And he's actually wanting to make three of these displays. So I suspect he would use arrays for the transistors and resistors if he decides to do it that way. I was really more interested in the multiplex version since it greatly reduces the parts count. But your method could also apply to that version. I just don't know what he plans to do about power.I am a bit curious about the emitter resistors in your circuit. Is there no chance that the voltage drop across them would be large enough that the PNPs would no longer be turned on fully by the 595s? I guess the alternative would be using collector and base resistors instead, which would be yet more resistors.

author: Benta
author_rank: Super Contributor
timestamp: October 03, 2024, 12:47:55 am
content: Quote from: Peabody on October 03, 2024, 12:18:52 amI think you need to find a "Transistors 101" somewhere. Just joking.The PNP plus emitter resistor is a wonderful current source that will provide a constant collector current to the load.Provided that the base voltage is constant. And it is: it's -3.3 V from the 'HC595.There is absolutely no need to use more resistors.BTW: decoupling caps etc. are not shown in my circuit. You'll need to add them.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 03, 2024, 01:53:58 am
content: Quote from: Peabody on October 02, 2024, 10:36:16 pmOk, well that's much easier then -- just do it! Don't sweat the small stuff. Make something, and if you see spooky behavior, come back with schematics, drawings, photos, etc., and we can probably spot the issue pretty quick. Maybe it needs a lot of rework (bad board layout?), but most likely it's just some resistors and capacitors in places. CMOS logic is pretty well conceived, it's hard to get wrong.Tim

author: BennoG
author_rank: Frequent Contributor
timestamp: October 03, 2024, 05:15:15 am
content: Quote from: Peabody on October 02, 2024, 05:01:26 pmThe shutter time can be short on stills at 30fps you you still have the problem.total frame rate can be 30 or 60 Hz, but the shutter at this frame rate can be 1/10000 that is where you thinking is going wrong.Benno

author: Psi
author_rank: Super Contributor
timestamp: October 03, 2024, 10:30:44 am
content: Quote from: Peabody on October 02, 2024, 05:01:26 pmYou still get pulsing at the beat frequency unless you're careful. It can be annoying and sometimes easier to just not deal with it at all and use DC.

author: Peabody
author_rank: Super Contributor
timestamp: October 03, 2024, 02:07:02 pm
content: Quote from: BennoG on October 03, 2024, 05:15:15 amOk, yes, I see what you mean. So indoors it might be ok, but in bright light it wouldn't, both at the same fps. Thanks for setting me straight on that.

author: Peabody
author_rank: Super Contributor
timestamp: October 03, 2024, 02:16:30 pm
content: Quote from: Benta on October 03, 2024, 12:47:55 amI'm usually the one teaching that course to rank beginners, and in fact have used the NPN version many times. But for some reason yesterday I just didn't recognize the Australian version. I was concerned that it would pinch off the current at a certain level, which of course is exactly what it does. Getting old, I guess.Anyway, while I think some form of multiplexing is completely workable here, it finally got through to me that it's not going to work for video and stills, at least not reliably. So, time to put the breadboard away. Thanks to everyone for all the comments and suggestions.

author: Peabody
author_rank: Super Contributor
timestamp: October 06, 2024, 03:58:10 pm
content: For the benefit of any future readers, it turns out that for common anode displays, the TLC5916 is the one to use. It can be controlled by a 3.3V MCU, and has a constant current driver on each pin cadjusted by a single resistor to ground on pin 15, so you don't even need to use individual segment resistors, and can adjust brightness with a pot. You can also adjust brightness via software, but either way, there's no flicker. About a dollar at Digikey/Mouser.

author: Benta
author_rank: Super Contributor
timestamp: October 06, 2024, 09:45:40 pm
content: Quote from: Peabody on October 06, 2024, 03:58:10 pmErm... it's a sink driver. Those are like sand on the beach. Do tell how it works with a CC display.

author: Peabody
author_rank: Super Contributor
timestamp: October 06, 2024, 09:55:30 pm
content: It's a sink driver with adjustable constant current output, which means you don't have to mess with the seven resistors. That feature is not common as far as I know. And as I said in my post, "for common anode displays..." So of course it doesn't work with CC. Not unless there's a CC version of this chip, which I haven't found.

author: Benta
author_rank: Super Contributor
timestamp: October 06, 2024, 10:10:17 pm
content: So:nota solution to this thread.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: October 07, 2024, 05:13:56 am
content: As I said above, industry of color led panels has special chips for any possible config you can imagine.