Troubleshooting

This chapter provides troubleshooting guidance for common issues listed below.

Connection Issues

Issue: Unable to connect to terminal

Possible causes:

• Incorrect COM port
• Device not detected
• Wrong communication parameters
  Solution:
• Verify COM port in Device Manager.
• Check cable and connection.
• Ensure baud rate, data bits, and stop bits match.

Issue: Terminal not detected

Possible causes:

• CDC mode not enabled
• USB cable not connected properly

Solution:

• Enable CDC mode on POS device.
• Reconnect USB cable.
• Restart device if required.

Transaction Issues

Issue: No response from terminal

Possible causes:

• Communication failure
• Incorrect request format
• Solution:
• Verify connection status.
• Ensure request ends with “!”.
• Check transaction type.

Issue: Transaction failed

Possible causes:

• Invalid data
• Signature mismatch
• Terminal error

Solution:

• Validate request data.
• Verify signature generation.
• Retry transaction.

Response Handling Issues

Issue: Unable to parse response

Possible causes:

• Incorrect response handling logic
• Corrupted data

Solution:

• Validate response format.
• Check LRC and data integrity.

General Issues

Issue: Terminal busy

Solution:

• Wait and retry.
• Use “Check Status” API before sending request.

Issue: Repeated failures

Solution:

• Restart terminal.
• Re-establish connection.
• Re-register terminal (legacy only).