UART TX DATA

Hi RMorais,

The provided example code for the MAX78002EVKit demonstrates a UART loopback test between UART1 and UART2, where:

• UART1 is configured to receive data asynchronously.
• UART2 is configured to transmit data synchronously.
• The example assumes a physical connection between UART1 and UART2:
  
    P0.12 (UART1_RX) <==> P1.1 (UART2_TX)
    P0.13 (UART1_TX) <==> P1.0 (UART2_RX)

If you are monitoring the UART lines using a logic analyzer or interfacing with a PC via UART, and you only connect to UART1, you will not observe any activity. This is because the code transmits data through UART2, not UART1.

In other words, if UART2 is not connected to the logic analyzer or PC, no TX activity will be visible. Additionally, UART1 RX will remain idle unless data is looped back from UART2 or received from an external source. The COM port acknowledgment you observed indicates that the UART peripheral is initialized but not necessarily transmitting any data on the UART1 lines.

To sum up: No activity is visible on the TX or RX lines connected only to one UART interface, and the Saleae logic analyzer will not capture any traffic if it is attached solely to UART1 or to the PC‑connected port. Although the COM port may appear active on the host computer, the example does not send data to the PC; it only verifies data transfer internally between the two UART modules.

For PC Communication: If the objective is to send or receive data directly between the evaluation kit and a PC, the example code must be modified. Specifically, only one UART instance (e.g., UART1) should be initialized and used with printf() or MXC_UART_Write() to transmit data to the PC‑connected UART interface. The loopback configuration involving UART2 should be removed in that case.

Kind regards,

Haluk