Important
This board uses a flow_control_pin, also called a talk_pin in the YamBMS documentation and used to manage the direction of data transmission for RS485 transceiver that do not handle this automatically. This talk_pin must be specified in your YAML.
The Waveshare ESP32-S3-RS485-CAN is an industrial-grade WiFi wireless communicator based on the ESP32-S3 microcontroller. This board is designed for professional IoT applications with built-in isolation and protection circuits, making it particularly well-suited for the YamBMS project thanks to its robust RS485 and CAN bus interfaces.
Key Features:
- Industrial-grade design with multiple protection circuits
- Isolated RS485 and CAN interfaces
- Built-in 120Ω termination resistors (jumper-selectable)
- Digital isolation to prevent signal interference
- Power supply isolation for stable operation
- Wide voltage input range (7-36V DC)
- DIN rail mountable protective enclosure
| Specification | Details |
|---|---|
| Microcontroller | ESP32-S3-WROOM-1 |
| Processor | Xtensa 32-bit LX7 dual-core @ up to 240MHz |
| FLASH | 16MB |
| PSRAM | 8MB |
| Wireless | Wi-Fi 802.11 b/g/n (2.4GHz) / Bluetooth 5.0 (LE) |
| RS485 | 1× Isolated RS485 interface |
| CAN Bus | 1× Isolated CAN interface |
| UART | 1x SH1.0 interface (not isolated) |
| Power Input (DC Terminal) | 7-36V DC (wide range) |
| Power Input (USB) | 5V via USB Type-C |
| Isolation | Power isolation + Optocoupler isolation |
| Termination | 120Ω resistors (jumper-selectable for RS485 & CAN) |
| LED Indicators | PWR, RS485 TX/RX, CAN |
| Enclosure | Rail-mounted ABS protective case |
| Programming | USB Type-C (firmware download & debugging) |
Based on hardware limitations and testing, this board supports:
| Interface | Maximum | Notes |
|---|---|---|
| CAN | 1x bus | CAN bus to BMS or Inverter |
| RS485 | 1x bus | Best option for monitoring many BMS of the same brand |
| UART | 3× devices¹ | Can be connected to the SH1.0 interface or GPIOs header (shared with RS485) |
| Bluetooth (BLE) | 3× devices¹ | BLE stack consumes significant RAM, may cause crashes/reboots |
¹ BMS / Balancer / Shunt
Note: These are theoretical limits. Not all combinations have been tested.
It would be possible to add one or more WK2168 4x UART expander to increase the number of UART port.
The Waveshare ESP32-S3-RS485-CAN can be powered using two methods:
- Connect a USB Type-C cable to the USB port
- Provides 5V power
- Recommended for programming, debugging, and testing
- Convenient for development and troubleshooting
- Voltage range: 7V to 36V DC (wide range)
- Connect to the dedicated power screw terminal
- Recommended for permanent installations and industrial environments
- Provides stable power with built-in voltage regulator
- Built-in power supply isolation provides stable isolated voltage
- No extra power supply required for the isolated terminal
Important:
- The board features integrated power isolation for enhanced safety and reliability
- Suitable for harsh industrial environments with voltage fluctuations
- Do not exceed the 36V maximum input voltage
The RS485 interface is isolated and clearly labeled on the board.
RS485 GPIO Pins (Internal):
- TX (GPIO17): RS485 transmit data
- RX (GPIO18): RS485 receive data
- EN (GPIO21): RS485 transceiver enable (automatic switching)
talk_in
RS485 Terminal Block Pinout: The RS485 port typically has a 2-pin screw terminal block:
- A (or +): RS485 A / Data+ (non-inverting)
- B (or -): RS485 B / Data- (inverting)
RS485 Features:
- Isolated interface to avoid external signal interference
- Automatic transceiver mode switching (no manual DE/RE control needed)
- Supports RS485 Modbus and other industrial protocols
- LED indicators:
- Green LED: Lights up when RS485 transmits data
- Blue LED: Lights up when RS485 receives data
The CAN interface is isolated and clearly labeled on the board.
CAN GPIO Pins (Internal):
- TX (GPIO15): CAN transmit (TWAI TX)
- RX (GPIO16): CAN receive (TWAI RX)
CAN Terminal Block Pinout: The CAN port typically has a 2-pin screw terminal block:
- H (or CANH): CAN High
- L (or CANL): CAN Low
CAN Features:
- Isolated CAN interface for easy access to various CAN devices
- Uses ESP32-S3 TWAI (Two-Wire Automotive Interface) controller
- LED indicator: Blinks during CAN data transmission
To connect an RS485 device to the RS485 port:
| RS485 | Terminal Block |
|---|---|
| A + | RS485 A+ (Data+ non-inverting) |
| B - | RS485 B- (Data- inverting) |
Wiring Steps:
- Identify the A and B wires from your RS485 device (may be labeled as D+/D-, A/B, or +/-)
- Connect the A wire (D+ / Data+) to the A+ terminal
- Connect the B wire (D- / Data-) to the B- terminal
- Connect the ground wire to the GND terminal for common reference
RS485 Best Practices:
- Always connect the ground (GND) to provide a common reference between devices
- The board features automatic transceiver mode switching, no manual control needed
- RS485 polarity matters: if communication fails, try swapping A and B connections
- Use twisted pair cable (recommended) to reduce noise and interference
- The isolation protects the ESP32-S3 from high-voltage interference on the RS485 bus
- Monitor communication using the green (TX) and blue (RX) LED indicators
To connect a CAN device to the CAN port:
| CAN bus | Terminal Block |
|---|---|
| CAN H | CAN H (CAN High) |
| CAN L | CAN L (CAN Low) |
Wiring Steps:
- Identify the CAN H and CAN L wires from your CAN device
- Connect the CAN H wire to the H (CANH) terminal
- Connect the CAN L wire to the L (CANL) terminal
- Connect the ground wire to the GND terminal for common reference (optional)
CAN Bus Best Practices:
- Always connect the ground (GND) for proper common mode voltage reference
- The board uses the ESP32-S3 TWAI (Two-Wire Automotive Interface) controller
- CAN bus requires proper termination (see Termination Resistors section below)
- Use twisted pair cable specifically designed for CAN bus (120Ω impedance)
- The isolation protects the ESP32-S3 from electrical noise on the CAN bus
- Monitor CAN communication using the CAN LED indicator (blinks during transmission)
- Typical CAN bus speeds: 125 kbps, 250 kbps, 500 kbps, or 1 Mbps
One of the key advantages of the Waveshare ESP32-S3-RS485-CAN is its built-in 120Ω termination resistors that can be enabled or disabled via jumpers.
The board includes an onboard 120Ω RS485 termination resistor.
How to Enable RS485 Termination:
- Locate the RS485 termination jumper on the board (typically labeled "RS485 120R" or similar)
- Move the jumper cap to the "120R" position to enable the termination resistor
- Move the jumper cap to the "NC" (No Connection) position to disable termination
When to Enable RS485 Termination:
- Enable termination if the board is at one of the two endpoints of the RS485 bus
- RS485 networks require 120Ω termination at both ends of the bus
- If the board is in the middle of the network, keep termination disabled (NC position)
- For short cable runs (<10 meters), termination may be optional but is still recommended
FAQ Note: If RS485 communication is not working, the Waveshare wiki recommends: "Please move the jumper cap to 120R and try again. Some RS485 devices require a 120R resistor to be connected in series."
The board includes an onboard 120Ω CAN termination resistor.
How to Enable CAN Termination:
- Locate the CAN termination jumper on the board (typically labeled "CAN 120R" or similar)
- Move the jumper cap to the "120R" position to enable the termination resistor
- Move the jumper cap to the "NC" (No Connection) position to disable termination
When to Enable CAN Termination:
- Enable termination if the board is at one of the two endpoints of the CAN bus
- CAN bus requires exactly two 120Ω termination resistors on the entire bus (one at each end)
- If the board is in the middle of the network, keep termination disabled (NC position)
- With proper termination, you should measure ~60Ω between CAN H and CAN L
Termination Tips:
- Always check termination settings before troubleshooting communication issues
- Many CAN devices (like inverters) have built-in termination - verify before adding more
- Incorrect termination is a common cause of CAN communication failures
The board includes several LED indicators for monitoring system status:
| LED | Color | Function |
|---|---|---|
| PWR | Red/Green | Power indicator - lights up when board is powered |
| RS485 TX | Green | Lights up when RS485 port sends data |
| RS485 RX | Blue | Lights up when RS485 port receives data |
| CAN | Yellow/Green | Blinks during CAN bus data transmission |
These indicators are extremely useful for troubleshooting communication issues in real-time.
For a typical YamBMS setup with the Waveshare ESP32-S3-RS485-CAN:
-
Power Supply:
- For bench testing: Connect USB Type-C cable (5V)
- For permanent installation: Connect 12V or 24V DC to screw terminal (recommended)
-
BMS Communication (RS485):
- Connect your BMS (e.g., JK, JBD, SEPLOS, PACE, BASEN) to the RS485 port
- Wire according to: A=RS485 A (Data+), B=RS485 B (Data-), GND=Ground
- Enable RS485 termination (120R jumper) if the board is at the end of the RS485 bus
- If the BMS is the only RS485 device, enable termination
-
Inverter Communication (CAN):
- Connect your inverter (e.g., Deye, Sofar, Growatt, Victron) to the CAN port
- Wire according to: H=CAN H, L=CAN L, GND=Ground
- Enable CAN termination (120R jumper) if the inverter is at the end of the CAN bus
- For point-to-point (board ↔ inverter), typically both ends need termination
- Check if your inverter has built-in termination before enabling
-
Verification:
- Power on the board - the PWR LED should light up
- Monitor RS485 communication using green (TX) and blue (RX) LEDs
- Monitor CAN communication using the CAN LED (should blink during transmission)
-
GPIO Pin Configuration:
- RS485: TX=GPIO17, RX=GPIO18, EN=GPIO21
- CAN: TX=GPIO15, RX=GPIO16
The Waveshare ESP32-S3-RS485-CAN comes with a rail-mounted ABS protective enclosure:
Enclosure Features:
- Industrial-grade ABS plastic case
- DIN rail mountable for easy installation in electrical cabinets
- Protects the board from dust, moisture, and physical damage
- Provides professional appearance for industrial installations
- Easy to install and safe to use
Installation:
- The case clips onto standard 35mm DIN rails
- Suitable for use in control panels, switchboards, and industrial enclosures
If you have trouble uploading firmware:
- Long press the BOOT button
- While holding BOOT, press the RESET button
- Release RESET, then release BOOT
- The module will enter download mode
- Now you can upload your firmware
This solves most download/flashing issues.
Waveshare provides demo firmware with a web interface:
- Default WiFi AP name: ESP32-S3-RS485-CAN
- Default password: waveshare
- The web interface allows control of RS485 and CAN ports
- You can get the device IP via Bluetooth debugging assistant
- Waveshare ESP32-S3-RS485-CAN Product Page
- Waveshare ESP32-S3-RS485-CAN Wiki
- Schematic Diagram (available on wiki)
- Check termination jumper - move to "120R" position if board is at bus endpoint
- Verify correct A/B wiring - try swapping if needed
- Check that ground (GND) is connected between devices
- Monitor green (TX) and blue (RX) LEDs to verify data transmission
- Ensure baud rate matches between all RS485 devices
- Test cable continuity and check for damaged twisted pair cable
- Check termination jumper - move to "120R" position if board is at bus endpoint
- Verify exactly two 120Ω termination resistors are present on entire CAN bus
- Check correct CAN H and CAN L wiring
- Verify ground (GND) is connected for common mode voltage reference
- Measure resistance between CAN H and CAN L (should be ~60Ω with proper termination)
- Monitor CAN LED - it should blink during transmission
- Verify CAN bus speed matches all devices (typically 125k, 250k, 500k, or 1Mbps)
- Enter download mode using BOOT + RESET button sequence (see Programming section)
- Verify USB cable supports data transfer (not charge-only)
- Check correct COM port is selected in IDE
- Try different USB cable or USB port on computer
- Ensure USB drivers are installed (CH343P chip)
- Verify power supply voltage is within 7-36V DC range (or 5V via USB)
- Check PWR LED lights up when powered
- Verify polarity of DC power connection
- Do not exceed 36V maximum input voltage
- The board's power isolation should prevent most power-related issues
- The board has built-in isolation for both power and communication interfaces
- If experiencing interference issues, verify:
- Ground connections are properly made
- Shielded cables are used in noisy environments
- Isolation jumpers are correctly configured
| Feature | Waveshare | LilyGo T-Connect |
|---|---|---|
| RS485 Ports | 1 (isolated) | Up to 3 (isolated) |
| CAN Ports | 1 (isolated) | 1 (isolated) |
| Built-in Termination | ✅ Yes (120Ω jumper-selectable) | ❌ No (external resistors required) |
| Power Isolation | ✅ Yes | ❌ No |
| Signal Isolation | ✅ Yes (RS485 & CAN) | ✅ Yes (RS485 & CAN up to 2500V) |
| Enclosure | ✅ DIN rail ABS case included | ❌ No enclosure |
| Power Input | 7-36V DC or USB-C | 7-12V DC or USB-C |
| LED Indicators | PWR, RS485 TX/RX, CAN | PWR, APA102 support |
| Price | Moderate | Moderate |
| Best For | Single RS485 + CAN with isolation | Multiple RS485 + CAN with isolation |
Summary: The Waveshare board excels in industrial-grade protection and built-in termination, while the LilyGo offers more RS485 ports and configuration flexibility. Choose based on your specific needs:
- Waveshare: Best for harsh environments, built-in termination, ease of installation
- LilyGo: Best for multiple RS485 devices, flexible configuration, compact size
License: This documentation is part of the YamBMS project and follows the same GPLv3 license.
Disclaimer: Always verify specifications and wiring with the official Waveshare documentation before deployment. This guide is community-created and may not reflect the latest product revisions.