In the store you can find an ESP32 board with the PCB outline and pinout of a Huzzah32. Normally my designs are original and try to maximize the functions that are available on the board pins. This board breaks with the tradition and is a clone of an existing design.

Why make a clone of another board? First and foremost it is not a straight copy of he original board, rather it is an improved version of the Huzzah32. The original has issues with the biggest two being the price and the power consumption in deep sleep mode. The current consumption in deep sleep mode is about 10uA. The battery voltage monitor is nearly identical to the original and has two 100k resistors in series with the center tap connected an ADC channel . In this design it would be the dominant power draw in Deep Sleep mode so I added a high side switch that disconnects the resistors from the LiPo-cell when the board is in sleep mode.

Other small changes are the addition of activity LEDs for the RX and TX signals of the USB to Serial converter, a cutout of the PCB underneath the printed antenna of the Wroom-32 module to restore the RF performance of the Wroom-32 module.

https://www.ezsbc.com/index.php/products/esp32-feather.html

Cell Voltage Measurement

There’s an extra step needed measure the cell voltage. By default the sense resistors are not attached to the cell since they would represent a constant current drain of about 20uA on the charged cell. The original Huzzah 32 design has such terrible deep sleep current consumption that the extra 20uA was not a big deal compared the the 2mA static load on the cell.

To turn on the voltage sensing IO-pin 2 has to be set high before the voltage is measured. After the voltage measurement IO-2 should be set low to conserve battery charge. When the ESP32 is put into deep sleep mode IO2 is automatically low so that the resistors are disconnected.