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This project demonstrates how to connect an ESP32 DevKit (Wemos, 32 pins) together with a MAX485 module to the Bambulab AMS (Auxiliary Material System).
It establishes RS485 serial communication between the AMS and the ESP32.
This code was used as a base and ported to the ESP32:
https://github.com/krrr/BMCU370
There is also OTA and WebSerial integrated for easier analysis, but first flash you have to do by wire. Additional information:
- https://wiki.bambulab.com/en/x1/troubleshooting/AMS_is_not_detected_by_the_printer
- https://github.com/Bambu-Research-Group/Bambu-Bus
- https://github.com/09lab/BambuBus-Sniffer
This wiring diagram covers Slot 0: one motor and one AS5600 sensor, using ESP32, MOSFET, LM7812 voltage regulator, and MAX485 for RS485 communication.
| Source/Module | Target/Module | Voltage / Notes |
|---|---|---|
| Bambulab AMS Pin 4 | LM7812 IN | 24 V Input |
| LM7812 OUT | MOSFET VIN | 12 V for Motor |
| LM7812 GND | ESP32 GND | Common Ground |
| MOSFET GND | ESP32 GND | Common Ground |
| ESP32 3.3 V | AS5600 VCC | Sensor Power |
| ESP32 3.3 V | MAX485 VCC | RS485 Transceiver |
| ESP32 Pin | Function | Connected to |
|---|---|---|
| GPIO32 | PWM_CH0 | MOSFET PWM_IN |
| GPIO22 | I²C SCL | AS5600 SCL |
| GPIO21 | I²C SDA | AS5600 SDA |
| GPIO16 | UART RX (RS485 RO) | MAX485 RO |
| GPIO17 | UART TX (RS485 DI) | MAX485 DI |
| GPIO5 | RS485 DE/RE Control | MAX485 DE/RE |
| GND | Ground | All modules |
| 3.3 V | Power | AS5600, MAX485 |
| Device / Module | Pin / Signal | Connection / Notes |
|---|---|---|
| AS5600 (Slot 0) | SCL | GPIO22 ESP32 |
| AS5600 (Slot 0) | SDA | GPIO21 ESP32 |
| AS5600 (Slot 0) | GND | ESP32 GND |
| AS5600 (Slot 0) | VCC | ESP32 3.3 V |
| MOSFET Module | PWM_IN | GPIO32 ESP32 (PWM_CH0) |
| MOSFET Module | VIN | LM7812 OUT (12 V) |
| MOSFET Module | GND | ESP32 GND |
| MOSFET Module | OUT+/OUT- | Motor (+/-), flyback diode recommended |
| Bambulab AMS | Pin1 B | MAX485 B |
| Bambulab AMS | Pin2 A | MAX485 A |
| Bambulab AMS | Pin3 GND | ESP32 GND |
| Bambulab AMS | Pin4 24V | LM7812 IN |
| MAX485 | RO | GPIO16 ESP32 (UART RX) |
| MAX485 | DI | GPIO17 ESP32 (UART TX) |
| MAX485 | DE/RE | GPIO5 ESP32 |
| MAX485 | VCC | ESP32 3.3 V |
| MAX485 | GND | ESP32 GND |
Bambulab AMS (6-Pin) MAX485 ESP32 (Wemos 32-Pin)
────────────────────── ──────── ─────────────────────
Pin 1 (A) ─────────────────────► A
Pin 2 (B) ─────────────────────► B
Pin 3 (GND) ────────────────────► GND ────────────────► GND
Pin 4 (24V) ── ✗ DO NOT USE
Pin 5 (NC) ── ✗
Pin 6 (NC) ── ✗
RO ────────────────► GPIO16 (RX)
DI ────────────────► GPIO17 (TX)
DE+RE ────────────────► GPIO5
VCC ───────────────► VIN (5V)
| ESP32 Pin | MAX485 Pin | Description |
|---|---|---|
| GPIO 16 | RO | RS485 → ESP32 (RX) |
| GPIO 17 | DI | ESP32 → RS485 (TX) |
| GPIO 5 | DE & RE | Direction control |
| GND | GND | Ground |
| VIN (5 V) | VCC | Power for MAX485 module |
According to Bambulab Wiki – AMS Connector Pinout:
| AMS Cable (6-Pin) | Signal | MAX485 Pin | Note |
|---|---|---|---|
| Pin 1 | B | B | RS485 differential signal |
| Pin 2 | A | A | RS485 differential signal |
| Pin 3 | GND | GND | Ground |
| Pin 4 | 24 V | ❌ Do not connect | |
| Pin 5 | NC | ❌ Not used | |
| Pin 6 | NC | ❌ Not used |
- Power supply: The MAX485 module is not powered from the AMS 24 V line. Instead, it is powered via the ESP32 VIN pin (5 V).
- Direction control: DE and RE on the MAX485 are tied together and connected to GPIO 5 of the ESP32.
- Logic levels: The MAX485 operates at 5 V, while the ESP32 GPIOs are 3.3 V tolerant → this is compatible, as the MAX485 understands 3.3 V TTL levels.
This project uses a dedicated Flash partition (storage) to persist data structures.
This ensures that settings remain available even after a restart or OTA update.
