We may want to save and later restore ESP8266 and ESP32 firmwares that came with them and were installed from the factory. It will come handy later on when we are troubleshooting the ESP development boards for possible defects.
We need the software Esptool to do this. Esptool is based on Python and so we need to first install Python.
If you are using Windows and do not have Esptool installed yet, please see the article entitled How to Install Esptool on Windows 10.
Gathering the Board’s Info
To properly save and restore an ESP8266 or an ESP32 firmware, we must be sure on the size of the flash chip involved.
To gather the board’s info, run the flash_id command.
Notice that we did not specify the port where the development board is connected. Esptool was smart enough to scan the different ports. It found that the board is connected on COM8.
On the screenshot above, I highlighted the important information with an arrow. The most important info we need is the flash size, which, in this particular case, is 4MB.
Save 1MByte or 8Mbit Flash
The command for saving the firmware of an ESP8266 or ESP32 chip with a 1MB (8Mbit) flash chip is as follows:
esptool.py --baud 115200 --port COM8 read_flash 0x0 0x100000 fw-backup-1M.bin
–baud 115200, the baud rate of the data transfer
–port COM8, the communications port where the board is connected
read_flash, the specific command
0x0, the starting address of the flash memory to read in hexadecimal
0x100000, the size of flash memory to read in hexadecimal (1048576 or 1MB decimal)
fw-backup-1M.bin, file name of the saved firmware
Save 4MByte or 32Mbit Flash
When saving the firmware of a development board with 4MB (32Mbit) of flash chip, we adjust the memory size parameter on the command. Hexadecimal 0x400000 is decimal 4194304 or 4MB.
esptool.py --baud 115200 --port COM8 read_flash 0x0 0x400000 fw-backup-4M.bin
Restore 1MByte or 8Mbit Flash
esptool.py --baud 115200 --port COM8 write_flash 0x0 fw-backup-1M.bin
Restore 4MByte or 32Mbit Flash
esptool.py --baud 115200 --port COM8 write_flash 0x0 fw-backup-4M.bin
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