bonanza-bridge-fw

bonanza-bridge-fw is RP2040 passthrough firmware for communicating with ASICs and board peripherals from a ESP32S3. The asic UART has been moved to PIO1 to support 9bit serial frames for the Intel BZM2 ASIC.

This firmware targets the bitaxeBonanza-1002x.

Developing

Install Rust:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

rustup target add thumbv6m-none-eabi

cargo install probe-rs-tools --locked
cargo install elf2uf2-rs --locked
cargo install cargo-binutils

For SWD-based development and debugging:

# Build the latest firmware:
cargo build --release

# Build, program, and attach to the device with RTT for debugging:
cargo run --release

# Just flash the device, don't attach to RTT:
cargo flash --release --chip RP2040

# Erase all flash memory:
probe-rs erase --chip RP2040 --allow-erase-all

For UF2-based development:

# Build the latest firmware:
cargo build --release

# Convert the ELF to an RP2040-compatible UF2 image:
elf2uf2-rs target/thumbv6m-none-eabi/release/bonanza-bridge-fw bonanza-bridge-fw.uf2

# Convert and deploy the UF2 image to an mounted RP2040:
elf2uf2-rs -d target/thumbv6m-none-eabi/release/bonanza-bridge-fw

Running

The bonanza-bridge-fw firmware exposes two hardware UART interfaces to the ESP32S3 and one PIO-based 9-bit UART to the ASIC. USB serial is not used by this firmware.

Serial Interfaces

Interface	RP2040 Peripheral	RP2040 Pins	Format	Baudrate	Purpose
Control Serial	UART0	TX: GPIO0, RX: GPIO1	8N1	115200	Fan control and board control commands
Data Serial	UART1	TX: GPIO4, RX: GPIO5	8N1	5000000	ESP32S3-side ASIC data stream
ASIC Serial	PIO1	TX: GPIO8, RX: GPIO9	9N1	5000000	BZM2 ASIC-side data stream

Data Serial

• Uses RP2040 UART1 on GPIO4/GPIO5.
• 8N1 on the ESP32S3 side and 9N1 on the BZM2 ASIC side.
• All data is passed through bidirectionally.
• The firmware currently uses a fixed baudrate of 5000000 on both sides.

8-bit to 9-bit Data Encoding:

Data is sent/received as pairs of bytes:

• First byte: Lower 8 bits of the 9-bit word (bits 0-7)
• Second byte: Bit 8 (only LSB is used, can be 0 or 1)

Examples:

• To send 0x155 (binary: 1_01010101): Send bytes [0x55, 0x01]
• To send 0x0AA (binary: 0_10101010): Send bytes [0xAA, 0x00]
• Received 9-bit data is sent to ESP32 in the same format

Note: The 9th bit can be used for addressing or protocol-specific purposes depending on your ASIC requirements.

Control Serial

• Uses RP2040 UART0 on GPIO0/GPIO1.
• Format is 8N1.
• The firmware currently uses a fixed baudrate of 115200.

Packet Format

0	1	2	3	4	5	6...
LEN LO	LEN HI	ID	BUS	PAGE	CMD	DATA

0. length low
1. length high
	- packet length is the number of bytes in the whole packet.
2. command id
	- Whatever byte you want. It will be returned in the response.
3. command bus
	- always 0x00
4. command page
	- GPIO: 0x06
	- Fan: 0x09
5. command 
	- varies by command page. See below
6. data
	- data to write. variable length. See below

Response Format

Responses are also length-prefixed:

0	1	2	3...
LEN LO	LEN HI	ID	DATA

• ID echoes the command ID from the request.
• DATA is the command response payload.
• Error responses use the same framing and return an error code in DATA[0].

Error Codes

• 0x10: timeout while receiving a packet
• 0x11: invalid command or malformed packet

Packet Timing

• Control packets should be sent as a continuous byte stream.
• A partial control packet that stalls for more than a few milliseconds is treated as a timeout error.

GPIO

Commands:

• 5v_en: 0x01
• asic_rst: 0x02
• asic_trip (read-only): 0x03

Data:

• [pin level] (omit for read operations)

Example:

• Set 5v_en High: 07 00 00 00 06 01 01
• Get asic_rst: 06 00 00 00 06 02
• Get asic_trip: 06 00 00 00 06 03

Fan

Commands:

• set speed: 0x10
• get tachometer: 0x20

Data:

• [speed percentage 0-100] (for set speed command)

Example:

• Set fan speed to 50%: 07 00 00 00 09 10 32
• Set fan speed to 100%: 07 00 00 00 09 10 64
• Read fan tach (RPM): 06 00 00 00 09 20