TM4C1294NCPDT: Disable UART Internal Loopback mode

CJ Boyer

Part Number: TM4C1294NCPDT

Working on an application that uses multiple UARTS for communication, and want to have a built in test that uses the Tivaware UARTLoopbackEnable, to run a simple loopback test to confirm data is being sent and processed correctly. However, I am not finding any kind of command to revert the change to internal loopback. What is the best practice for this?

Solutions I've thought of but haven't tested yet are as follows:
Disabling all the UARTs after the built in test, and reenabling them, Hoping they come up in a default manner.
Having the board restart after a successful built in test (Not a good solution for this).
Not using internal loopback for the built in test.

Any advice would be appreciated.

over 2 years ago

0 Charles Tsai over 2 years ago

TI__Guru**** 191906 points

Hi,

For some reason there is no API to disable the loopback mode. However, reading the source code of UARTLoopbackEnable, it is a matter of setting the UART_CTL_LBE bit to enable loopback. After you finish the loopback test, you can use HWREG to clear UART_CTL_LBE manually in UART_O_CTL register.

//*****************************************************************************
//
//! Enables internal loopback mode for a UART port
//!
//! \param ui32Base is the base address of the UART port.
//!
//! This function configures a UART port in internal loopback mode to help with
//! diagnostics and debug. In this mode, the transmit and receive terminals of
//! the same UART port are internally connected. Hence, the data transmitted
//! on the UnTx output is received on the UxRx input, without having to go
//! through I/O's. UARTCharPut(), UARTCharGet() functions can be used along
//! with this function.
//!
//! \return None.
//
//*****************************************************************************
void UARTLoopbackEnable(uint32_t ui32Base)
{
//
// Check the arguments.
//
ASSERT(_UARTBaseValid(ui32Base));