Modding Pimoroni +/-24v ADC module to use a different i2c address?

Discussion Electronics
1

Hi! I’ve been using several of the Pimoroni +/-24v ADC modules in my Eurorack synth projects, with great success.

According to the schematic, cutting the address selection pad that connects the “address select” pin to GND leaves the address select pin connected to VDD - but on the actual device it seems to go first through a component I don’t recognise that can be seen in the product image (marked ‘103’, so maybe a resistor pack of some kind?).

The datasheet for the ADC1015 says that its possible to configure two additional addresses, by connecting the address select pin to SDA or SCL instead, and I want to ‘unlock’ those extra addresses (as I want to have 2+ ADCs and also have another i2c device on the same bus that uses 0x48 and can’t be changed).

Has anyone made this modification on the Pimoroni +/24v ADC board, or able to give some clues on how this could be achieved? I presume it should be possible by identifying the correct trace and adding a jumper to the desired pin, but I could do with a second opinion on where to cut and solder before I ruin a board!

Thanks in advance to anyone who can advise!

2

The 103 is a resistor code and you read it as 10*10^3, so you see a 10kΩ resistor. This is a pullup to VDD. But since it is also connected to GND, the level of ADDR_SELECT will be low as long as you don’t cut the trace to GND. And indeed you see a resistor pack in the product image. The other resistors in the pack are used for pullups on SCL, SDA and INT.

I don’t think you can mod this, because you would have to cut the ADDR_SELECT trace to VDD.
And this is an expensive device.

Suggestion: use an I2C multiplexer, Pimoroni has a few different units. I once ran a large BME280 tests with seven devices, all with the same I2C address behind a single PCA9548. Worked like a charm. This is much cheaper than modding the ADC directly.