PROCESSOR-SDK-AM68A: Unable to Get Response from SPI Communication on AM68a with SX1262

Hello,

Most of the team members are out of office. Please expect delayed response.

- Keerthy

Thank you Keerthy,

I wanted to clarify some observations based on further testing of the SPI communication issue in the AM68a processor.

• The data is being sent from the MISO pin (pin 21), not the MOSI pin (pin 19), which is the main issue. The MOSI pin does not send the expected data, while MISO is showing the transmitted data.
• The logic analyzer confirms that data is being sent correctly, but it’s appearing on the wrong pin (MISO) instead of MOSI.

I have futher tested with sample python code.

Test Setup:

• MOSI (pin 19) and MISO (pin 21) are connected to the logic analyzer.
• I sent some test data ([0x48, 0x65, 0x6C, 0x6C, 0x6F] which corresponds to "Hello").
• The Python spidev library was used, and SPI was set to mode 0 with a speed of 50 kHz.

• import spidev
  import time
  
  # SPI device parameters
  SPI_BUS = 0         
  SPI_DEVICE = 0      
  SPI_MODE = 0        
  SPI_SPEED_HZ = 50000 
  
  # Create an SPI object
  spi = spidev.SpiDev()
  
  def setup_spi():
      """
      Initialize the SPI interface.
      """
      # Open SPI bus and device
      spi.open(SPI_BUS, SPI_DEVICE)
      spi.mode = SPI_MODE
      spi.max_speed_hz = SPI_SPEED_HZ
      print(f"SPI initialized: Bus={SPI_BUS}, Device={SPI_DEVICE}, Mode={SPI_MODE}, Speed={SPI_SPEED_HZ} Hz")
  
  def send_and_receive(data):
      print(f"Sending: {data}")
      response = spi.xfer2(data)  # Transfer data
      print(f"Received: {response}")
      return response
  
  def main():
      try:
          setup_spi()
  
          while True:
              # Test data to send
              test_data = [0x48, 0x65, 0x6C, 0x6C, 0x6F]  # ASCII for "Hello"
  
              response = send_and_receive(test_data)
  
              try:
                  decoded_response = ''.join(chr(byte) for byte in response if 32 <= byte <= 126)
                  print(f"Decoded Response: {decoded_response}")
              except Exception as e:
                  print(f"Error decoding response: {e}")
  
              # Wait before sending the next transaction
              time.sleep(1)
  
      except KeyboardInterrupt:
          print("\nExiting...")
      finally:
          spi.close()
          print("SPI closed.")
  
  if __name__ == "__main__":
      main()
  

Results:

• The data is being successfully sent from the SPI bus.
• However, the data is coming from the MISO pin (pin 21), not the MOSI pin (pin 19) as expected. The MISO pin shows the correct data, but MOSI stays idle.
• The logic analyzer confirmed this: MISO is sending the data, but MOSI is not.

Questions:

1. Is there a pin configuration issue on the AM68a that could cause the MISO and MOSI pins to behave this way?
2. Are there any additional debugging steps I can try to resolve this issue?

Thanks in advance for any help!

Hi,

It has been over two weeks since I raised this query on the SPI communication issue in the AM68a processor. I would appreciate a response to clarify the unexpected behavior observed with the MISO and MOSI pins as outlined in my earlier post.