TL866 II PLUS/Bootloader
The TL866 II PLUS has a bootloader installed at the start of the internal flash which is used to update the firmware. The hardware reset vector (the instruction at 0000h) points to the bootloader. On each boot the bootloader inspects various state (TBD) and determines whether it should execute itself to allow firmware updates or jump into the main firmware.
The process of reverse engineering the bootloader is still ongoing.
Commands
Reset
Command 3F seems to be used to reset the device. When used from the stock firmware the device resets into the bootloader, and when used from the bootloader the device resets to the stock firmware.
| Offset | Field | Size | Value | Description |
|---|---|---|---|---|
| 0 | command | 1 | 3F | the command identifier |
| 1 | reserved | 7 | 0 | reserved, set to zero |
When resetting from the stock firmware, another command is transmitted first. This may be some kind of key required to permit reset? Unknown until the firmware is dumped and analyzed.
| Offset | Field | Size | Value | Description |
|---|---|---|---|---|
| 0 | command | 1 | 3D | the command identifier |
| 1 | reserved | 3 | 0 | reserved, set to zero |
| 4 | key? | 4 | 86 B9 78 A5 | unknown, maybe just a fixed key? Set statically in the official client. |
Report
The report command requests that the firmware identify itself.
| Offset | Field | Size | Value | Description |
|---|---|---|---|---|
| 0 | bCommand | 1 | 00 | the command identifier |
| 1 | reserved | 7 | 0 | reserved, set to zero |
The device will respond with a 64-byte structure:
| Offset | Field | Size | Value | Description |
|---|---|---|---|---|
| 0 | bCommand | 1 | 00 | the command, echoed |
| 1 | bStatus | 1 | ?? | which firmware is running: 01 is the stock firmware, 02 is the bootloader |
| 4 | bFwVersionMinor | 1 | ?? | firmware version minor part: 00.0.xx |
| 5 | bFwVersionMajor | 1 | ?? | firmware version major part: 00.x.00 |
| 40 | bDeviceVersion | 1 | ?? | firmware version device part: xx.0.00 |