ESP Offline Programmer Uses microSD Card to Flash ESP32/ESP8266 Modules

The ESP Offline Programmer is an ESP32-based device designed to flash firmware onto ESP32 or ESP8266 modules without requiring a PC. It features an ESP32-WROOM-32E module, a microSD card slot for storing firmware, a USB-C port for power and programming, and a CH340C USB-to-serial chip for communication with target modules.

It includes a 6-pin header (Tx/Rx, DTR/RTS, 3.3V, and GND) for automatic bootloading, along with reset and upload buttons and three status LEDs. This tool is particularly useful for remote deployments and mass programming, allowing users to flash multiple modules faster than traditional PC-based methods. Programming jigs for ESP32 and ESP8266 modules simplifies the process.

ESP Offline Programmer Specifications

• Wireless module – Espressif Systems ESP32-WROOM-32E
  • CPU – ESP32 dual-core Tensilica LX6 microcontroller
  • Storage – 4MB flash
  • Connectivity – 2.4 GHz WiFi and Bluetooth LE, built-in PCB antenna
• Storage – microSD card slot for offline firmware flashing
• USB – USB Type-C port for power and programming the built-in ESP32 module
• Target module connection
  • USB-to-serial chip – CH340C for communication with target ESP32/ESP8266 modules
  • 6-pin header
    • Tx/Rx
    • DTR/RTS for automatic bootloader (controls GPIO0 and EN of ESP32/ESP8266)
    • 3.3V and GND
• Buttons & Indicators
  • Boot button for built-in ESP32
  • Reset and Upload buttons
  • 3x status LEDs
• Power Supply – 5V via USB Type-C
• Dimensions – TBD

The project is partially open-source, with schematics and firmware available on Hackster.io and GitHub, leveraging Espressif’s esp-serial-flasher code for compatibility with other MCUs like STM32, Raspberry Pi Pico, and Zephyr OS-based microcontrollers.

The ESP Offline Programmer can be purchased in India at a price of ₹1,499 (approximately USD 17.5), while the ESP32 and ESP8266 programming jigs are priced at around ₹465.25 (around USD 5.5) which are sold separately. However, at the time of writing the shipping is limited to local shipping within India. For international buyers, alternatives like the upcoming ESP Offline Flasher by MeatPi Electronics, set to launch via Crowd Supply, may provide a similar solution with global availability. This offline programmer was first brought to our attention through cnx-software.

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