SPI and led panel

[Tang]

Hello

I'm using 4x sure electronics led display (based on HT1632C chip with a 74HCT138N mux) with my raspi using SPI and after a while (4-10 hours) I got the last led panel that displays nothing. I need to halt raspi and restart it to make the panel works again
I tested a lot of thing thinking it was an issue in my code, but nothing gave result unfortunately
I suspect a spidev library issue but i don't know why.

My tests were to:
- change xfer2 function parameters (increase delay, change speed)
- add some pause in my code (time.sleep)
- change spi port frequency

I changed order of panels, and it's always the last one that stops working, so i suppose it's not a hardware issue.
Configuring my system with 3 led panels instead of 4 seems to work (i only tested 24 hours).
The problem seems to occur when i'm scrolling message permanently. If i display a static message, i can reproduce the problem. But the spi is used only once, when the message is displayed.
I got no errors when the panel is not working, my software still send data to it correctly (spi returns no error)

If someone have some ideas, i will take it
For now, i'm using writebytes instead of xfer2 closing/opening spi at each scrolling.

Thank you

[ghp]

Hello,
when three modules work reliable, but not four modules, then power supply could be an issue. Do you have a separate supply for the modules with enough power ?
Check SPI speed. The driver chip allows for 1MHz write clock, 500kHz read clock, but its always safe to be slower. Avoid long cables.
Check ground connections.
Regards,
Gerhard

[Tang]

Hi Gerhard

I use same power supply for both led panels and raspi. It's a 5v/3A power supply, more than expected for those kind of panel if I read correctly the datasheet (http://sure-electronics.net/download/DE ... 1.0_EN.pdf) 0.36A max per panels.

I'm just testing with separated power supplies (5v/3a for leds and 5v/2a for raspi).
And I will try with shorter cables and lower speed.

Thank you for your advices

Tang

[Tang]

After one more week of investigations, same results:
- 3 leds panels worked during 3 days with continous scrolling message
- with 4 leds panels, the last panel stops working after few hours
I reduced cable length (15-20cm instead of 50-60cm)
And I reduced spi speed from 1M to 500K

I will try with a new powerful power supply (more than 3A) asap.