e-Paper and old Raspberry Pi B V2.0 -- C code works, but python doesn't

I have a 7x5 v2 board that works great with my Pi 4. I tried to use it with a much older Pi B V2.0.

What works:

• The C test code here (epd) works fine when I configure it with USELIB_RPI=USE_BCM2835_LIB This confirms that I have attached the device propertly to the Pi device

What does not work:

• The C test code here (epd) does not work when I configure it with USELIB_RPI=USE_WIRINGPI_LIB
• The python code does not work.

In both of these cases, there is no error displayed, but the waveshare device is not updated.

@timc995 I am experiencing the same issue. I am using a RPi 2B and the c-code works perfectly fine with the BCM2835 library, whereas the python version doesn't yield any response from the screen. I don't get any errors from running the python code either. Any luck finding a solution to this issue?

Hi Daniel. Unfortunately I haven't got it to work. You're the first to reply to me. I think it must be an error with the waveshare library. I looked for the source code for the drivers but I didn't find it so I gave up. Tim

On Sun, Apr 3, 2022 at 9:50 PM Daniel Stubbs @.***> wrote:

@timc995 https://github.com/timc995 I am experiencing the same issue. I am using a RPi 2B and the c-code works perfectly fine with the BCM2835 library, whereas the python version doesn't yield any response from the screen. I don't get any errors from running the python code either. Any luck finding a solution to this issue?

— Reply to this email directly, view it on GitHub https://github.com/waveshare/e-Paper/issues/230#issuecomment-1087028650, or unsubscribe https://github.com/notifications/unsubscribe-auth/AABU4DVI2CXCHG2BLQVMQNTVDJDERANCNFSM5PSC4PSA . You are receiving this because you were mentioned.Message ID: @.***>

Tim,

I was able to get it working today. To be honest, I am not sure exactly what solved the issue. As part of my troubleshooting, I wired the MOSI to MISO pins on the RPi to create a loopback on the SPI interface. My first attempt was using the spidev-test program available at: https://github.com/rm-hull/spidev-test. I got nothing but zeros back on the SPI bus, so I started to suspect that something was wrong with the spidev library. To further troubleshoot, I installed the "pigpiod" and "pigpio-tools" packages. With those installed you can run sudo pigpiod pigs spio 0 50000 0 pigs spix 0 1 2 3 4 and you should get a response of "4 1 2 3 4". I got the correct response, which meant the SPI bus was working and further pointed to some issue with spidev. At that point I installed the "spi-tools" package to try and do some more troubleshooting with spidev. With the spi-tools package, you can use the spi-pipe program to do a similar loopback test as with pigpio as echo "test" | spi-pipe -d /dev/spidev0.0 | cat and you should see "test" echoed to your terminal.

At this point spidev-test and the python version of the epd codes started to work as expected. I am not sure what part of this process fixed the issue. I thought that maybe one of the packages I installed brought in some needed dependency, but even after uninstalling those packages, things still seem to be working. I will say that the first time I tried the spi-pipe command, I got garbage back. Upon rebooting things seemed to be working. Hopefully some of this information can help someone else figure out their issue. If I get bored, I might try with a fresh install of Raspbian to see if I can't nail down exactly where the problem lies.

I'm now motivated to start over. I'm pretty sure I reused the SD card, but I will spin another image up and see if I can replicate your success! I'd love to find a use for this very old Pi device, and driving an epaper display would be great.

On Mon, Apr 4, 2022 at 7:32 PM Daniel Stubbs @.***> wrote:

Tim,

I was able to get it working today. To be honest, I am not sure exactly what solved the issue. As part of my troubleshooting, I wired the MOSI to MISO pins on the RPi to create a loopback on the SPI interface. My first attempt was using the spidev-test program available at: https://github.com/rm-hull/spidev-test. I got nothing but zeros back on the SPI bus, so I started to suspect that something was wrong with the spidev library. To further troubleshoot, I installed the "pigpiod" and "pigpio-tools" packages. With those installed you can run sudo pigpiod pigs spio 0 50000 0 pigs spix 0 1 2 3 4 and you should get a response of "4 1 2 3 4". I got the correct response, which meant the SPI bus was working and further pointed to some issue with spidev. At that point I installed the "spi-tools" package to try and do some more troubleshooting with spidev. With the spi-tools package, you can use the spi-pipe program to do a similar loopback test as with pigpio as echo "test" | spi-pipe -d /dev/spidev0.0 | cat and you should see "test" echoed to your terminal.

At this point spidev-test and the python version of the epd codes started to work as expected. I am not sure what part of this process fixed the issue. I thought that maybe one of the packages I installed brought in some needed dependency, but even after uninstalling those packages, things still seem to be working. I will say that the first time I tried the spi-pipe command, I got garbage back. Upon rebooting things seemed to be working. Hopefully some of this information can help someone else figure out their issue. If I get bored, I might try with a fresh install of Raspbian to see if I can't nail down exactly where the problem lies.

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@dstubbs95 Thank you, i followed all your steps as described, even tho i did not recieve the same output as you during the pigpio tests after all steps the default waveshare examples started to work on my raspi!

so this worked: install pigpio and (re)start pigpiod > install pigpio-tools > install spi-tools > reboot > 'sudo systemctl restart pigpiod' > try examples again

Hey, I'm having the a similar issue on my Raspi 4B and found that a reboot reliably fixes it while, while the c code reliably causes it. Could someone verify that this is in fact the same problem?

Sequence of events to reproduce:

• start up raspi
• run sudo python3 epd_XXXXX.py -> screen updates
• run sudo ./epd -> screen updates
• run sudo python3 epd_XXXXX.py -> no response from screen
• run sudo ./epd -> screen still updates
• reboot
• run sudo python3 epd_XXXXX.py -> screen updates
• rinse and repeat.

Had the same problem getting the Python demo located at ~/e-Paper/RaspberryPi_JetsonNano/python/examples/epd_2in13_V3_test.py to work.

But for some reason, the magic lines by @dstubbs95 got it working:

sudo apt-get install -y pigpiod pigpio-tools spi-tools
sudo pigpiod
pigs spio 0 50000 0
pigs spix 0 1 2 3 4
echo "test" | spi-pipe -d /dev/spidev0.0 | cat

Running the demo now works on my Raspberry Pi Zero W:

(cd ~/e-Paper/RaspberryPi_JetsonNano/python/examples && sudo python3 epd_2in13_V3_test.py)

@dstubbs95 @bkahlert Thank you so much for this! I had exactly the same problem - the C demo was working fine but the display was blank when running the Python demo. The above solution worked a treat!