CYDs & ESP32 C3 Super Mini

All three of these devices are powered by an ESP32.

📷 Show photo

Three ESP32 devices

The ESP32 is smaller than a quarter!

📷 Show photo

ESP32 C3 Super Mini

Here's a quick walk through of what Aaron taught me:

The ESP32 C3 Super Mini is a tiny, affordable microcontroller board based on the ESP32-C3, a RISC-V single-core chip with Wi-Fi and Bluetooth built in.

Flashing MicroPython

Flash the MicroPython firmware using esptool:

esptool write_flash -z 0x0 ESP32_GENERIC_C3-20260406-v1.28.0.bin

Sample output:

Warning: Deprecated: Command 'write_flash' is deprecated. Use 'write-flash' instead.                           
esptool v5.3.0                                                                                                 
Connected to ESP32-C3 on /dev/ttyACM0:                                                                         
Chip type:          ESP32-C3 (QFN32) (revision v0.4)                                                           
Features:           Wi-Fi, BT 5 (LE), Single Core, 160MHz, Embedded Flash 4MB (XMC)                            
Crystal frequency:  40MHz                                                                                      
USB mode:           USB-Serial/JTAG                                                                            
MAC:                e8:3d:c1:8b:ac:84                                                                          
                                                                                                               
Stub flasher running.

Configuring flash size...
Flash will be erased from 0x00000000 to 0x001a5fff...
Wrote 1725008 bytes (1035498 compressed) at 0x00000000 in 4.4 seconds (3126.9 kbit/s).
Hash of data verified.

Hard resetting via RTS pin...

Connecting via Serial REPL

Once flashed, connect to the board's REPL over serial:

python3 -m serial.tools.miniterm /dev/ttyACM0 115200

Press Ctrl+] to exit miniterm.

Sample session (that is silly because it is so simple):

--- Miniterm on /dev/ttyACM0  115200,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
4*5
20
>>> a␛[␛[K
>>> 2*3
6
>>> a=['a','b','c']
>>> a
['a', 'b', 'c']
>>>

CYD - Cheap Yellow Display

The CYD can range in price between $5 and $25. In 2024 Reddit pointed to BuyDisplay.com as a place to find places to buy. I'm lazy and paid $17 for mine about a year ago on Amazon.com.

📷 Show photo

CYD Box

Tonight (17 June 2026) flashed micropython to a CYD and loaded a clock program that uses WiFi to connect to an NTP server:

python -m venv ./venv source venv/bin/activate pip install esptool esptool chip-id

https://micropython.org/download/ESP32_GENERIC/

esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash 0x1000 ESP32_GENERIC-20260406-v1.28.0.bin

python3 -m serial.tools.miniterm /dev/ttyUSB0 115200

We have a REPL!

Those commands are from https://micropython.org/download/ESP32_GENERIC/ and some claude. IOU a badly written blog post. This is that post. One day it might get better and will hopefully turn into a workshop people can play through.

git clone https://github.com/payne/cyd17June2026.git

This needs an .env file that is not in the repo:

WIFI_SSID=your wifi
WIFI_PASSWORD=its password
  1. pip install mpremote
  2. mpremote connect /dev/ttyUSB0 cp ili9341.py :ili9341.py # for fonts
  3. mpremote connect /dev/ttyUSB0 cp clock.py :clock.py # our clock program
  4. mpremote connect /dev/ttyUSB0 cp .env :.env
  5. mpremote connect /dev/ttyUSB0 run clock.py
📷 Show photo

it is working


Tags: esp32, learning, electronics, fun

← Back home