RS485 communication problem on Verdin AM62 with Ivy Carrier board

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Hello,

Based on your setup with the Verdin AM62 on the Ivy Carrier Board, your configuration looks correct for accessing UART2 (1). The Verdin AM62 modules are compatible with the Ivy Carrier Board and support RS-485 communication (1).

Verifying RS-485 Hardware Support

First, confirm that RS-485 is properly enabled on your system. The Ivy Carrier Board supports RS-485 on UART_2 with transceiver functionality (1). You can verify the device tree configuration is loaded correctly since you mentioned using the Ivy device tree.

Potential Issues and Solutions

1. Device Tree RS-485 Configuration

While you’re using the Ivy device tree, RS-485 mode might need explicit enabling. Based on similar issues reported with Verdin modules on Ivy boards (2), you may need to ensure RS-485 is properly configured in the device tree or enable it programmatically.

2. Hardware Connection Verification

The issue where you’re receiving 0x00 bytes instead of your transmitted data suggests a potential hardware or configuration problem. This could be related to:

  • Transceiver Direction Control: The RS-485 transceiver needs proper direction control to switch between transmit and receive modes (3)
  • Signal Levels: Ensure your RS-485 to USB converter is properly connected and configured

3. Software Configuration Enhancement

Try modifying your Python script to explicitly configure RS-485 settings:

import sys
import serial
import serial.rs485
import time

def test_rs485_loopback():
    ser = serial.Serial("/dev/verdin-uart2", 9600, 8, 'N', 1, timeout=1)
    ser.reset_input_buffer()
    ser.reset_output_buffer()
    
    if not ser.is_open:
        ser.open()

    if ser.is_open:
        # Configure RS-485 with more explicit settings
        rs485_settings = serial.rs485.RS485Settings(
            rts_level_for_tx=True,
            rts_level_for_rx=False,
            delay_before_tx=0.001,
            delay_before_rx=0.001,
            loopback=False
        )
        ser.rs485_mode = rs485_settings
        
        print("Serial port opened successfully.")
        print(f"Port: {ser.name}")
        print(f"RS485 mode: {ser.rs485_mode}")
        
        test_data = b'Hello RS485'
        time.sleep(0.01)
        bytes_written = ser.write(test_data)
        ser.flush()  # Ensure data is transmitted
        time.sleep(0.05)
        
        print(f"Wrote {bytes_written} bytes: {test_data}")
        s = ser.read(len(test_data))
        print(f"Read {len(s)} bytes: {s}")
        
        ser.close()

if __name__ == "__main__":
    test_rs485_loopback()

4. Debugging Steps

  1. Check RS-485 Status: Verify if RS-485 mode is actually enabled by checking the serial port settings
  2. Test with Simple UART: Try the same code without RS-485 settings to see if basic UART communication works
  3. Hardware Verification: Use an oscilloscope or logic analyzer to verify signal transmission on the RS-485 lines

5. Alternative Configuration

If the device tree approach doesn’t work, you might need to configure RS-485 using ioctl calls directly, as mentioned in community discussions (2). This would involve using lower-level system calls to configure the UART for RS-485 operation.

Container Configuration

Your Docker container configuration looks correct for accessing the UART device. The device mapping and group permissions should allow access to /dev/verdin-uart2 (1).

Try the enhanced script above and let us know if you still encounter issues. The key is ensuring proper RS-485 transceiver control and verifying that the hardware connections are correct.

Best regards, Toradex AI Assistant.