ESP32

ESP32 microcontroller

- Adafruit HUZZAH32 – ESP32 Feather Board, https://www.adafruit.com/product/3405 - based on ESP-WROOM-32 module, uses ESP32-D0WDQ6 chip, https://en.wikipedia.org/wiki/ESP32 - ESP32 chip is a very basic microcontroller, CPU is done by same people who did MIPS CPUs. - ESP32 is supported by "Mongoose OS", familiar with it as we already use the mongoose web server from same people.

- board available from DigiKey quantity "hundreds" ~CAD$35

 https://www.digikey.ca/product-detail/en/adafruit-industries-llc/3405/1528-2181-ND/7244967
 https://www.digikey.ca/product-detail/en/adafruit-industries-llc/3591/1528-2514-ND/8119805

- ESP-WROOM-32 module

 general page: https://www.espressif.com/en/products/hardware/modules
 product page: https://www.espressif.com/zh-hans/esp-wroom-32/resources (in Chineese)
 data sheet: https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32_datasheet_cn.pdf (in Chineese)
 data sheet: https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32_datasheet_en.pdf (English)
 from adafruit: https://www.adafruit.com/product/3405 and
 https://learn.adafruit.com/adafruit-huzzah32-esp32-feather

 - 240 MHz CPU, 520 kbytes SRAM, Wifi, Bluetooth, 4 Mbyte flash, interface for SD card.
 - 3x UART
 - 3x SPI
 - 2x I2C
 - 12 ADC inputs
 - 2 DAC
 - more goodies
 - everything is 3.3V, *NOT* 5V safe

- https://learn.adafruit.com/adafruit-huzzah32-esp32-feather/pinouts

 - USB power connector
 - connection for external 3.7 V battery, charged from USB
 - serial IO 3.3V RX+TX
 - 1x SPI (where is the rest?)
 - 1x I2C (where is the rest?)
 - 7 GPIO top, shared with 2 DACs and 6 ADCs
 - 7 GPIO bottom, shared with 7 ADCs and other functions
 - everything is 3.3V, *NOT* 5V safe
 - there is ADC1 and ADC2, not clear what it means, ADC voltage range not clear
 - ADC1 or ADC2 cannot be used with Wifi (this is unclear)
 - ESP32 SD card interface not connected
 - ESP32 serial IO connected to USB via USB-serial-bridge chip (the best I can tell)

 - power is USB with battery backup, one header pin provides regulated 3.3 V power to user (available current not clear, maybe 250 mA)

, battery voltage is on A13

 - suggest use with Ardiuno BSP (not mongoose OS)

- module schematic: https://cdn-learn.adafruit.com/assets/assets/000/041/630/original/feather_schem.png?1494449413