Hardware_Parts Selection_external_ADC
The ESP8266 has an internal 10-bit ADC that I originally planned to use for the temperature probe measurements, which led to a number of problems that I spent a considerable amount of time trying to manage through my design
- Poor ADC measurement accuracy
- A single analog input pin
- 0-1 V ADC measurement scale which is substantially below the 3.3V working voltage of the ESP8266 microcontroller
Overcoming these issues took me down time consuming design rabbit-holes to develop solutions:
- accuracy - no great solutions but I looked into filtering and oversampling
- single analog pin - multiplexing
- ADC voltage scale - designed, simulated and tested an opAmp based level shifting subcircuit to shift voltages to the required range
I eventually had the epiphany that all of these major issues could be easily sidestepped by dumping the idea of using the esp8266 ADC and moving to a low cost external ADS1015 ADC module. The advantages of the ADS1015 are further discussed in the Design Consideration section.
ADS1015 12-bit I2C ADC Module
