A cute Python utility to communicate with the ROM bootloader in Espressif ESP8266. It is intended to be a simple, platform independent, open source replacement for XTCOM.
This is a work in progress; it is usable but expect some rough edges.
This utility actually have a user interface! It uses Argparse
and is rather self-documenting. Try running esptool -h.
Or hack the script to your hearts content.
The probably most useful command; writing an application to flash:
./esptool.py write_flash 0x000000 wi07c.rom
Creating an application image:
./esptool.py make_image -f app.text.bin -a 0x40100000 -f app.data.bin -a 0x3ffe8000 -f app.rodata.bin -a 0x3ffe8c00 app.flash.bin
Dumping the ROM:
./esptool.py dump_mem 0x40000000 65536 iram0.bin
If GPIO0 and GPIO15 is pulled down and GPIO2 is pulled high when the module leaves reset, then the bootloader will enter the UART download mode. It communicates over 115200 8N1.
The bootloader protocol uses SLIP framing.
Each packet begin and end with 0xC0, all occurrences of 0xC0 and 0xDB inside the packet
are replaced with 0xDB 0xDC and 0xDB 0xDD, respectively.
Inside the frame, the packet consists of a header and a variable-length body. All multi-byte fields are little-endian.
| Byte | Name | Comment |
|---|---|---|
| 0 | Direction | Always 0x00 for requests |
| 1 | Command | Requested operation, according to separate table |
| 2-3 | Size | Size of body |
| 4-7 | Checksum | XOR checksum of payload, only used in block transfer packets |
| 8..n | Body | Depends on operation |
| Byte | Name | Comment |
|---|---|---|
| 0 | Direction | Always 0x01 for responses |
| 1 | Command | Same value as in the request packet that trigged the response |
| 2-3 | Size | Size of body |
| 4-7 | Value | Response data for some operations |
| 8..n | Body | Depends on operation |
| Byte | Name | Input | Output |
|---|---|---|---|
0x02 |
Flash Download Start | total size, 0x200, block size, offset | |
0x03 |
Flash Download Data | size, sequence number, data. checksum in dedicated field. | |
0x04 |
Flash Download Finish | reboot flag? | |
0x05 |
RAM Download Start | total size, packet size, number of packets, memory offset | |
0x06 |
RAM Download Finish | execute flag, entry point | |
0x07 |
RAM Download Data | size, sequence numer, data. checksum in dedicated field. | |
0x08 |
Sync Frame | 0x07 0x07 0x12 0x20, 0x55 32 times |
|
0x09 |
Write register | Four 32-bit words: address, value, mask and delay (in microseconds) | Body is 0x00 0x00 if successful |
0x0a |
Read register | Address as 32-bit word | Read data as 32-bit word in value field |
Each byte in the payload is XOR'ed together, as well as the magic number 0xEF.
The result is stored as a zero-padded byte in the 32-bit checksum field in the header.
The firmware file consists of a header, a variable number of data segments and a footer. Multi-byte fields are little-endian.
| Byte | Description |
|---|---|
| 0 | Always 0xE9 |
| 1 | Number of segments |
| 2-3 | Padding/unused |
| 4-7 | Entry point |
| 8-n | Segments |
| Byte | Description |
|---|---|
| 0-3 | Memory offset |
| 4-7 | Segment size |
| 8...n | Data |
The file is padded with zeros until its size is one byte less than a multiple of 16 bytes. A last byte (thus making the file size a multiple of 16) is the checksum of the data of all segments. The checksum is defined as the xor-sum of all bytes and the byte 0xEF.
The boot rom writes a log to the UART when booting. The timing is a little bit unusual: 75000 baud (at least on my modules, when doing a cold boot)
ets Jan 8 2014,rst cause 1, boot mode:(3,7)
load 0x40100000, len 24236, room 16
tail 12
chksum 0xb7
ho 0 tail 12 room 4
load 0x3ffe8000, len 3008, room 12
tail 4
chksum 0x2c
load 0x3ffe8bc0, len 4816, room 4
tail 12
chksum 0x46
csum 0x46
This information is collected through research by Fredrik Ahlberg. Feel free to contact me on GitHub or through fredrik at z80 dot se.
This document and the attached source code is released under GPLv2.