Best ESP8266 -03 Firmware

The ESP8266-03 module on the Cactus Micro rev2 has a 512Kb flash chip. What is the best firmware that fits the flash chip. Espressif 0/1.X.X or ai-thinker-vX-X.X.X.bin


When did you buy the Cactus Micro? The ESP-03 module has 1Mb flash in new batch Cactus Micro. We use default ai-thinker- at previous board.

Here’s a list

The new Espressif AT firmware also work. But the AT command need a “\r\n” suffix. The hardwareSerialMonitor sketch can’t work with it.

Bought my 2 Cactus Micro’s some 3 weeks ago from Tindie. Tried to find information about the ESP-03 module that’s used on the Cactus. It seems only the ESP-12 has a 1-2 or even 4 Mb flash all others have a 512Kb flash according to the information I could find.

Aprilbrother has stated that all new Cactus Micro’s will be flashed with Espruino firmware. I already wrote a big chunk of code using AT commands so when my Cactus is flashed with Espruino I need to know which AT firmware is the most steady one and what firmware size I can (re)flash into the ESP-03. I tried to read the text on the ESP-03 flash chip to check out the flash size but that is almost impossible. This is the first information about an 1Mb flash size on the ESP-03 module I got. Is there a way to verify the size ?


Our vendor replace all flash chip to 1Mb on ESP-03 since 09/2015. The flash size is 1Mb if you bought recently.

Please download the firmware ai-thinker- to it.