Troubleshoot auto phat on coral mini dev

Robotics
1

Hi,

I am trying to get started with an auto phat on a coral mini dev board, but I am having problems. The coral mini dev is very similar to the coral dev board, but the I2C device number 3 is connected to the pin 3 and 5 instead of device 1 on the coral dev board:

mendel@silly-rabbit:~$ pinout
             3.3.V -> 1    2 <- 5V
  I2C1_SDA (i2c-3) -> 3    4 <- 5V
  I2C1_SCL (i2c-3) -> 5    6 <- GND

I could not connect to the servo driver, so I checked the available devices on the i2c bus:

mendel@silly-rabbit:~/dev/python$ sudo i2cdetect -y 3

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- 5d -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

This would indicate that only the motor driver is available, there should be other services at 0x40, 0x73 and 0x69.

I have looked at the protocol, the phat does not seem reply on these addresses

i2cshot.png
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The analogue levels look ok to me

I don’t know what else to check, the two boards don’t seem to play together. Does this look like a faulty phat?

i2osz.png
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2

Just to add a little bit more info, I have done some more checks with another master (using an ESP32 with arduino). An I2C scan now shows more active addresses (0x5D,0x69 and 0x73, while 0x40 is still missing). Randomly I get errors in the protocol (SDA changing state when SCL is high), maybe 1 out of 1000 writes.

I have also tried to go down to a 10kHz clock, but the problem persists (0x40 resulting in NACK in all cases and random protocol errors ).

3

No hints from tech staff? I’d love to get this to function properly rather then returning the board.

4

Unfortunately this product wasn’t designed for or tested on a coral mini dev and we don’t have much in the way of suggestions.

Other users that have been able to get it running, please feel free to share any solutions you might have.

5

I don’t understand what you mean by “designed for”. The product page of the auto phat board mentions the coral dev board as well as other boards to be usable with it. These boards just talk I2C with the phat, so a correct I2C implementation should be the only requirement on both sides, or am I missing something?

6

We mention Jetson Nano and Google Coral on the product page because they both have the same 40 pin GPIO connector that the Auto pHAT has and are at least electrically compatible but there could be software or constraints that a user would need to work through to get the pHAT completely working. The Auto pHAT has only been tested on a Raspberry Pi and the Coral Mini Dev isn’t mentioned at all on the list.

You might try reducing the I2C bus speed on your Coral Mini Dev to see if that brings the other sensors on line, if the bus speed is too fast, they might not be responding.