RGB LED PCB Help

HeroXLazer · 02 Mar 2017, 03:36

So, I want to use a LED driver with RGB LEDs, and I want to use SMD RGB LEDs that only have four pins. They have a R pin, a G pin, a B pin, and a VCC pin. The driver I'm going to use uses Charlieplexing, and I'm confused on how to Charlieplex with single pins. I figured out to do it if you have two pins on each LED, but not with one pin. Could someone please explain how to wire it to the driver?
MCU: http://www.atmel.com/Images/Atmel-7766-...ummary.pdf LED Driver: http://www.issi.com/WW/pdf/31FL3731C.pdf RGB in LED Driver Example: http://www.issi.com/WW/pdf/31FL3732.pdf RGB LEDs: http://www.lumex.com/sml-lx0404siupgusb

anorak · 02 Mar 2017, 08:55

Looks like LEDs with common anode. Should be no problem to wire them as in the documentation. Just think of the one VCC pin as three pins.

You can have a look at this schema: https://github.com/anorak-47/keyboard_p ... orak_91tkl
It uses an 31FL3733 and 4-pin LEDs. Beware, it is completely untestet!

HeroXLazer · 02 Mar 2017, 15:39

Thank you very, very much.

HeroXLazer · 02 Mar 2017, 15:49

anorak wrote: Looks like LEDs with common anode. Should be no problem to wire them as in the documentation. Just think of the one VCC pin as three pins.

You can have a look at this schema: https://github.com/anorak-47/keyboard_p ... orak_91tkl
It uses an 31FL3733 and 4-pin LEDs. Beware, it is completely untestet!

But, each of the LEDs is a single pin, so what about that?

anorak · 02 Mar 2017, 18:50

For my PCB with RGB LED support, I plan to use throug-hole-LEDs like those available from Zeal PC (https://zealpc.net/collections/accessor ... rough-hole). They have 4 pins, a common anode, and a cathode for each color. That is the same pinout as for the smd RGB LED from the datasheet you linked.

So, you want to use a ISSI IS31FL3731 for driving the RGB LEDS. Hope you are aware that you can only drive 32 RGB LEDs per IS31FL3731, as noted in the application note for the 3171 (http://www.issi.com/WW/pdf/31FL3731_App_Note.pdf). As you can see from the app note, you can think of the RGB LED as three LEDs with a common anode (VCC) and three cathode pins. I only used the IS31FL3731 for monochorme LEDs, so I do not now wether it will work. But there is an 60% PCB using two IS31FL3731 to drive the SMD RGB LEDs: https://zealpc.net/collections/group-bu ... /zeal60rgb Looks like what you want to do. A fork of the qmk_firmware for the Zeal60 PCB is also available: https://github.com/Wilba6582/qmk_firmware/tree/zeal60 But the files for the PCB are not available, I think.

I deceided to use the ISSI IS31FL3733 that has much better RGB LED support. It can drive up to 64 RGB LEDs and has a much easyer wiring schema. I ordered some vom mouser.de and shipping is estimated for end of april...

vinnycordeiro · 06 Mar 2017, 19:16

anorak wrote: For my PCB with RGB LED support, I plan to use throug-hole-LEDs like those available from Zeal PC (https://zealpc.net/collections/accessor ... rough-hole). They have 4 pins, a common anode, and a cathode for each color. That is the same pinout as for the smd RGB LED from the datasheet you linked.

So, you want to use a ISSI IS31FL3731 for driving the RGB LEDS. Hope you are aware that you can only drive 32 RGB LEDs per IS31FL3731, as noted in the application note for the 3171 (http://www.issi.com/WW/pdf/31FL3731_App_Note.pdf). As you can see from the app note, you can think of the RGB LED as three LEDs with a common anode (VCC) and three cathode pins. I only used the IS31FL3731 for monochorme LEDs, so I do not now wether it will work. But there is an 60% PCB using two IS31FL3731 to drive the SMD RGB LEDs: https://zealpc.net/collections/group-bu ... /zeal60rgb Looks like what you want to do. A fork of the qmk_firmware for the Zeal60 PCB is also available: https://github.com/Wilba6582/qmk_firmware/tree/zeal60 But the files for the PCB are not available, I think.

I deceided to use the ISSI IS31FL3733 that has much better RGB LED support. It can drive up to 64 RGB LEDs and has a much easyer wiring schema. I ordered some vom mouser.de and shipping is estimated for end of april...

I'm almost finishing a design precisely like that: 60% keyboard PCB with 4 pins TH RGB LED support, controlled by the ISSI IS31FL3733 LED driver. Do you know if the QMK fork for the IS31FL3731 will work with this one? (Firmware programming is my Achilles' heel.)

HeroXLazer · 06 Mar 2017, 23:38

vinnycordeiro wrote:
anorak wrote: For my PCB with RGB LED support, I plan to use throug-hole-LEDs like those available from Zeal PC (https://zealpc.net/collections/accessor ... rough-hole). They have 4 pins, a common anode, and a cathode for each color. That is the same pinout as for the smd RGB LED from the datasheet you linked.

So, you want to use a ISSI IS31FL3731 for driving the RGB LEDS. Hope you are aware that you can only drive 32 RGB LEDs per IS31FL3731, as noted in the application note for the 3171 (http://www.issi.com/WW/pdf/31FL3731_App_Note.pdf). As you can see from the app note, you can think of the RGB LED as three LEDs with a common anode (VCC) and three cathode pins. I only used the IS31FL3731 for monochorme LEDs, so I do not now wether it will work. But there is an 60% PCB using two IS31FL3731 to drive the SMD RGB LEDs: https://zealpc.net/collections/group-bu ... /zeal60rgb Looks like what you want to do. A fork of the qmk_firmware for the Zeal60 PCB is also available: https://github.com/Wilba6582/qmk_firmware/tree/zeal60 But the files for the PCB are not available, I think.

I deceided to use the ISSI IS31FL3733 that has much better RGB LED support. It can drive up to 64 RGB LEDs and has a much easyer wiring schema. I ordered some vom mouser.de and shipping is estimated for end of april...
I'm almost finishing a design precisely like that: 60% keyboard PCB with 4 pins TH RGB LED support, controlled by the ISSI IS31FL3733 LED driver. Do you know if the QMK fork for the IS31FL3731 will work with this one? (Firmware programming is my Achilles' heel.)

I'm using the same LED driver, and I was wondering the same question. I'm so confused on firmware.

anorak · 07 Mar 2017, 08:34

The 3733 is not compatible to the 3731/3732. It uses slightly different registers to store the led enable and PWM values. So there are at last some changes needed for the code writing the PWM values to the 3733. AFAIK there is until now no firmware supporting the 3733. I started to writing some code based on the tmk_firmware, but I am at the very beginning now and still do not have my 3733 samples. My PCB is in production now...

HeroXLazer · 05 Apr 2017, 01:32

anorak wrote: The 3733 is not compatible to the 3731/3732. It uses slightly different registers to store the led enable and PWM values. So there are at last some changes needed for the code writing the PWM values to the 3733. AFAIK there is until now no firmware supporting the 3733. I started to writing some code based on the tmk_firmware, but I am at the very beginning now and still do not have my 3733 samples. My PCB is in production now...

I know this is a long time after, but I realized that you have diodes going from the anode to the pins. Why do you need a diode? Also, have you figured out the firmware?