I was having trouble to get an i2c device working - after spending a day debugging/trouble shooting it looks like its not detecting the address 0x51. If I changed the address of the device its detected properly. Is this address reserved for something?
I'm using I2C-2 and have verified several other i2c devices at different addresses and they all work.
Just to give a list of things I've done:
1) Checked VGP and made sure all the GPIO settings are correct
2) Checked that it was the right SDA and SCL lines
3) Checked that the voltage (3.3v is correct)
4) Checked the voltage/pullup/pulldown was correct
5) Tried I2C-7 as well
6) Checked that the 0x51 address works on a raspberry pi 5 and on an RP2040 microcontroller (they do)
I can easily change the address through jumpers but I thought I'd ask here - and also make this topic just in case anyone else has similar issues.
If I changed the address of the device its detected properly.
This shoud not happen, because the address itself does not change the way Vivid Unit detects a I2C device.
As far as I know, Vivid Unit itself does not use the 0x51 address on I2C-2 bus. If the address 0x51 has been occupied, you can see it when running the i2cdetect command.
It's quite a coincidence that we do have a product that uses 0x51 as I2C address, and it is the Witty Pi 5 HAT+. We actually have tested it with the Vivid Unit, and it gets detected properly:
vivid@vivid-unit:~$ sudo i2cdetect -y 2
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
vivid@vivid-unit:~$
Interesting - Nothing was showing up at 0x51 on i2c-2 (or any of the other i2c busses). Seems like its just a fluke in this case. Luckily I can just jump the device to a different address so things are working as expected now.