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RGBMatrix support for 64x64 panels on Feather M4?
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RGBMatrix support for 64x64 panels on Feather M4?

by tslagle on Tue Apr 28, 2020 3:37 pm

It seems like there is CircuitPython RGBMatrix support for 64x64 LED panels for the Raspberry Pi but not (for example) the Feather M4. Is there a limitation that prevents driving 64x64 panels from the M4? I know that the RGB Matrix Featherwing doesn't have the E address pin wired but it seems like a jumper could be added easily enough.

Thanks - looking forward to programming the panels in CircuitPython!

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by jepler on Tue Apr 28, 2020 4:51 pm

I haven't tried it personally (I only have a 16x32 and a 32x64 board), but the code is intended to support it. You're right that you'll have to make modifications to the featherwing, cutting a GND trace and hooking it to the Feather pin you designated as ADDR_E using the provided through-holes as a mini-protoboard area. Then, in the source code, you'd add that pin at the end of the addr_list. Of course, it will take more memory and processing time away from your CircuitPython program

Give it a try, and let us know the result!

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by tslagle on Tue Apr 28, 2020 6:25 pm

Thanks a lot, that's encouraging! I didn't want to buy a panel if it was known not to work. I'll order some and post if/when I have it working.
--Tim Slagle

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by memcbride on Mon May 18, 2020 7:00 pm

jepler wrote:I haven't tried it personally (I only have a 16x32 and a 32x64 board), but the code is intended to support it. You're right that you'll have to make modifications to the featherwing, cutting a GND trace and hooking it to the Feather pin you designated as ADDR_E using the provided through-holes as a mini-protoboard area. Then, in the source code, you'd add that pin at the end of the addr_list. Of course, it will take more memory and processing time away from your CircuitPython program

Give it a try, and let us know the result!


I'm relatively inexperienced in these hardware mods so I'm not sure what you mean by "cutting a GND trace...." I think I understand picking another pin to use for ADDR_E and making the connection via the prototyping area. Just not sure about that first part :-) Could somebody help explain further?

Thank you.

Mark

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by tslagle on Mon May 18, 2020 10:24 pm

Pin 8 that is used for ADDR_E on the 64x64 panels is designated as GND on smaller LED arrays. I can't see where pin 8 is grounded on the feather wing PCB but if it is, that connection would need to be cut so that another pin on the feather could drive it without being shorted to GND. I haven't received my 64x64 matrix yet, so this is just based on looking at the pictures of the boards.

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by memcbride on Mon May 18, 2020 10:30 pm

tslagle wrote:Pin 8 that is used for ADDR_E on the 64x64 panels is designated as GND on smaller LED arrays. I can't see where pin 8 is grounded on the feather wing PCB but if it is, that connection would need to be cut so that another pin on the feather could drive it without being shorted to GND. I haven't received my 64x64 matrix yet, so this is just based on looking at the pictures of the boards.


Okay. Now I understand. I'll investigate to see if I can figure out where it might be cut.

Thank you.

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by jepler on Mon May 18, 2020 10:47 pm

OK, yes, according to the schematic from our learn system, the pins 8 and 16 that are sometimes used as additional "address" pins are unconnected on the RGB Matrix Featherwing, so you can simply solder a jumper wire from the pin you want to use to to the spot next to the address pin. I think the Adafruit displays are "pin 8" but I did not verify that.


Image

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by memcbride on Tue May 19, 2020 12:52 pm

jepler wrote:OK, yes, according to the schematic from our learn system, the pins 8 and 16 that are sometimes used as additional "address" pins are unconnected on the RGB Matrix Featherwing, so you can simply solder a jumper wire from the pin you want to use to to the spot next to the address pin. I think the Adafruit displays are "pin 8" but I did not verify that.


From the RGB Featherwing learning guide, the pin usage is:
"Here are the following 'default' pinouts:
CLK on #13
LAT on #0 (a.k.a RX)
OE on #1 (a.k.a TX)
Address A on A5
Address B on A4
Address C on A3
Address D on A2
R1, G1, B1, R2, G2, B2 on 6, 5, 9, 11, 10, 12 in that order
That leaves A0, A1, SCK, MOSI, MISO, SDA, SCL available...."

Would there be a recommended pin such as A1 or D4? I was unable to locate whether pin 8 or 16 on the display is appropriate. The Circuitpython RGBMatrix library can handle up to 30 RGB pins and 8 addr pins according to its documentation.

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by memcbride on Tue May 19, 2020 8:53 pm

jepler wrote:OK, yes, according to the schematic from our learn system, the pins 8 and 16 that are sometimes used as additional "address" pins are unconnected on the RGB Matrix Featherwing, so you can simply solder a jumper wire from the pin you want to use to to the spot next to the address pin. I think the Adafruit displays are "pin 8" but I did not verify that.


From the learning guide for the Raspberry Pi RGB Hat on how to set the E addr jumper on the hat for a 64x64 panel:

"Melt a blob of solder between the center “E” pad the “8” pad just above it (for 64x64 matrices in the Adafruit shop)…or the “16” pad below (rare, for some third-party 64x64 matrices…check datasheet)."

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by memcbride on Wed May 20, 2020 1:49 pm

memcbride wrote:
jepler wrote:OK, yes, according to the schematic from our learn system, the pins 8 and 16 that are sometimes used as additional "address" pins are unconnected on the RGB Matrix Featherwing, so you can simply solder a jumper wire from the pin you want to use to to the spot next to the address pin. I think the Adafruit displays are "pin 8" but I did not verify that.


From the learning guide for the Raspberry Pi RGB Hat on how to set the E addr jumper on the hat for a 64x64 panel:

"Melt a blob of solder between the center “E” pad the “8” pad just above it (for 64x64 matrices in the Adafruit shop)…or the “16” pad below (rare, for some third-party 64x64 matrices…check datasheet)."


Ok. By connecting A1 to the E pad of the RGB board, I was able to use the 64x64 board with the Feather M4 Express and the feather RBGMatrix hat. In CircuitPython, the Conway example was considerably slower than a 32x32 board because of the four-fold increase in the number of pixels being handled. The Arduino RGB_matrix_Panel library does not support the 5 addr lines so I couldn't check if performance would be faster there.

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by jepler on Wed May 20, 2020 5:26 pm

This lib for Arduino should be capable of 64x64: https://learn.adafruit.com/adafruit-pro ... ix-library

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Re: RGBMatrix support for 64x64 panels on Feather M4?

by memcbride on Thu May 21, 2020 9:46 am

jepler wrote:This lib for Arduino should be capable of 64x64: https://learn.adafruit.com/adafruit-pro ... ix-library


Cool. I will check it out.

Thanks!

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Please be positive and constructive with your questions and comments.