ESP32

The ESP32 development boards are not without their problems.  Why keep using them anyway?  The ESP32 IC only costs €2.31/pce on Digikey.  Design a decent breakout board and done!

Well, if you don't want to design your own board, have a look at the Olimex ESP32-DevKit-LiPo.  The version without antenna costs <€10, while it includes a LiPo charger.  Moreover, it seems to be designed properly and it consumes only about 60µA in deep sleep (using a buck converter!).

Andreas Spiess ESP32 boards overview
Reduce the ESP32 Power Consumption : boards comparison

Ai-Thinker NodeMCU-32S	Wemos LOLIN32 Lite	Wemos D1 mini
fits on a breadboard Improvements: * needs a 100nF from #EN to GND to fix firmware upload problem. * pin labels only on bottom side KS0413 keyestudio ESP32 Core Board Use the ESP32-IO board (Keyes KS0465) for easy breadboarding and pin labels platformio : NodeMCU-32S holds a ESP32-WROOM-32D Chip is ESP32D0WDQ6 (revision 1) module Digikey (€8.25) schematic Velleman VMA109 AI-Thinker nodemcu_32s    AliExpress AliExpress	discontinued platformio : lolin32 AliExpress blog         AliExpress	AliExpress AliExpress

Ai-Thinker NodeMCU-32S

3V3 LDO

This module has a very poor performing AMS1117-3.3 (Iout=1A, dropout voltage = 1.1V).  The

If you want a SOT23-5 package, you can use the Richtek RT9080-33GJ5 has a 2µA quiescent current.  Has only 310mV dropout voltage and can deliver up to 600mA.  In case it's not available, you can order the ME6211C33M5G from AliExpress (40µA dropout voltage and pin compatible to the RT9080).

The ESP32 consumes 380mA peak.

Great resource about ESP32 boards and their power consumption.

Patch for firmware upgrade

• Which ESP32 pins are safe to use? Excel sheet
  • pin 14 remains 500ms high at power up.
• not 5V tolerant (although it might work a while)
• ESP32-WROOM-32D
  • 4MB SPI-flash by default (8MB &16MB) available on Digikey
  • no SPI-ram
  • 240MHz
• Micropython
  • https://github.com/espressif/esptool : pip3 install esptool
  • download & install Micropython : https://micropython.org/download/esp32/
  • Getting started with Micropython on ESP32
  • REPL will be available on virtual COM-port (/dev/ttyUSB0)
  • IDE : Visual Studio Code with micropy-cli
  • rshell :
    • rshell -p /dev/ttyUSB0
      • cp main.py /pyboard
      • rsync . /pyboard
    • repl : start repl
    • Ctrl-D in repl : soft reboot, restart program
    • Ctrl-C in repl : stop running program and return to prompt
    • Ctrl-X in repl : back to rshell
• Arduino
  • VSPI-port is default SPI-port.
• More popular platform than the nRF52840 (20x google search results)
• Bluetooth 4.2 + Wifi 2.4GHz
• Programming : C++, Python
• Easier ESP8266 Development (most might be applicable to ESP32 too)
• low power modes: 100nA (power off) to 10µA (RTC + RAM retention)
• slow FPU, not suitable for codec2 (see Andreas Schweiz)

TTGO LoRa32 T3_V1.6

• Schematic

nRF52840

• Long Range Bluetooth 5, Bluetooth mesh, ANT, 802.15.4, Thread, Zigbee
• 64 MHz Cortex-M4 with FPU
• existing codec2 implementation on nRF52832 (which has same CPU)
• 1 MB Flash, 256 KB RAM
• Programming : C++, Python
• low power modes: 400nA (power off) to 3.2µA (RTC + RAM retention)

LoRa boards

• SX1278 (137MHz to 525MHz)
• SX1276 (137MHz to 1020MHz)

RisingHF RHF76-052

• Product info
• Bands : 868MHz (less power) & 434MHz (most power)

RisingHF RHF78-052

• Bands: 434MHz only
• EC-Buying Ali Store : €5.34/pce
  

RAK Wireless RAK811

• RAK811 ($11), directly from RAK Wireless (+$24 shipping) (more expensive on AliExpress)