Raspberry Pi Forums

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

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

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

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.