I am working on a project that uses a Arduino MKR GSM 1400 and a ADXL335 Accelerometer . I am having trouble setting a interrupt wake up event on one of the GSM's interrupt-capable pin due to the analog nature of the ADXL335's output. The axis outputs typically range between ~1.4V-~2.2V with ~1.65V being the resting voltage level.
I have tried using a NTE987 op-amp to amplify the analog output enough to trigger a CHANGE on the interrupt pin I'm using. This resulted in the analog signal outputted by the ADXL335 boosting to a certain voltage level and not varying at all with any motion.
My current solution, which works very well but is not ideal for power consumption reasons, is using a smaller micro controller with less power draw's ADC to interpret the ADXL335's output and send digital wake-up signals to the GSM when certain thresholds are met. I would like to know if there's a better way to do this, as using an additional microcontroller to wake up the original microcontroller feels like a kludge.
