The accelerometer is a simple Kionix KXSC4 10227 2410, three axis accelerometer.
1.6V is the zero output. The accelerometers have a scale of about .250V/g. Assuming that the chip is able to go full scale, from 0V to 3V, this gives an absolute output of +-6g. That's perhaps a little high for my purposes, but it should be able to give pretty decent resolution with the STM32's 12-bit ADC.
There is a 30mV voltage spike every 125us (in other words, at 8MHz). This frequency doesn’t seem to be present at any of the pin inputs, which implies that there is some kind of digital noise either due to the accelerometer’s analog outputs or the microcontroller’s ADC inputs.
Table of notable pins