Expander Pi not showing up on Pi 3 Model B

Hi

I hav had tne Expander Pi for some time but only recently got round to setting it up. I carefully soldered the GPIO connector and the battery holder to the board. I have not connected the board to the Pi without a good battery installed. Follwed the tutorials but no luck accessing board.

Raspberry Pi 3 Model b

Raspbian Bullseye 32 bit

SPI and i2c enabled

Expander Pi v2.1

No other devices connected

sudo i2cdetect -l
i2c-1 i2c bcm2835 (i2c@7e804000) I2C adapter
i2c-2 i2c bcm2835 (i2c@7e805000) I2C adapter

The above is the same with or without the Expander Pi connected

sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Again the output is the same with or without the Expander Pi connected

Any ideas?

Thanks

John

Hi John

Can you try measuring the voltage between the 5V and GND pins on the Expander Pi to check that it is getting voltage from the Raspberry Pi? You could also try downloading our Expander Pi python library and running the ADC or DAC demos to check if the SPI bus works.

You should see two devices listed on i2cdetect with or without a battery fitted to the Expander Pi. As you do not see any devices, that would suggest a problem either with the configuration of the I2C bus on the Raspberry Pi or a hardware problem on the Expander Pi.

Can you review the steps in our [url=/kb/article/1/i2c-part-2-enabling-i2c-on-the-raspberry-pi[/url] again to ensure everything is configured correctly on the Raspberry Pi? If that does not help, try reflowing the solder on the GPIO pins, focusing on pins 1 to 6 next to the JUMPER label on the PCB. It could be a dry joint or a solder bridge between the I2C GPIO pins stopping it from working.

Thanks for the response

I had already checked the voltage between 5V and GND on the Expander Pi and there is 5V.

When you say "You should see two devices listed on i2cdetect with or without a battery fitted to the Expander Pi. As you do not see any devices, " what do you mean by devices? I have not installed the Expander Pi without a battery as per the warning on the product page.

Thinking that my soldering could be the issue I purchased one of these:

https://thepihut.com/products/mini-rtc-module-for-raspberry-pi

I get the same result, nothing shows up wih i2cdetect.

I have gone through the tutorial many times to check that I have followed it correctly.

I will try the Expander Pi python library.

John

When you run sudo i2cdetect -y 1 with the Expander Pi connected it should detect the MCP23017 IO chip on address 20 and the RTC on address 68 as shown below.


0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --


If the other RTC module you bought is also not showing up on i2detect, that would suggest a problem with the I2C bus on the Raspberry Pi rather than problems with the Expander Pi and Mini RTC module.

Do you have a spare SD card you could use to set up a fresh install of the Raspberry Pi OS? It is possible that your current installation has a configuration issue or a part of Linux has corrupted, stopping the I2C bus from working.

If a new install of Raspberry Pi OS does not work, the most likely cause is a hardware fault on the Raspberry Pi I2C hardware.

Hi

Thanks for your help.

The problem was with the Raspberry Pi itself, the GPIO connector is not working. I managed to buy a new Pi 4B and the Expander Pi works fine on that.

John