PN7462AU HSU UART – Is RTS/CTS Hardware Flow Control Enabled by Default

[uday_gowda]

Hello Team,

I am working with PN7462AU, using HSU UART through HIF initialization. I would like to clarify whether RTS/CTS hardware flow control is enabled by default when using HSU UART on PN7462.

I am not explicitly enabling hardware flow control in firmware. However, I observed that UART transmission appears to depend on the CTS line state, and I would like to understand whether HSU/HIF internally enables or depends on RTS/CTS by default.

Questions:

1. Is RTS/CTS hardware flow control enabled by default for HSU when phhalHif_Init() is called with E_HIF_HSU?

2. Does phhalHif_Init() or HSU internally configure TX to wait for CTS?

3. If flow control is enabled by default, how can it be disabled completely?

4. Are there specific APIs or registers to disable RTS/CTS dependency?

My current HSU initialization is:

void Hif_UartInit(void)
{
    gHifConfig.eInterface = E_HIF_HSU;

    gHifConfig.sConfig.sHsuConfig.bIsHsuBoot  = 0;
    gHifConfig.sConfig.sHsuConfig.bBaudRate   = E_HSU_BAUDRATE_115_2K;
    gHifConfig.sConfig.sHsuConfig.bStopBits   = 1;
    gHifConfig.sConfig.sHsuConfig.bDummyBytes = 0;
    gHifConfig.sConfig.sHsuConfig.bEOF        = 32;

    gHifConfig.bTimeout       = 0;
    gHifConfig.eBufferType    = E_BUFFER_FORMAT_FREE;
    gHifConfig.bShortFrameLen = 0;
    gHifConfig.bStoreErrData  = 0;
    gHifConfig.bHeaderSize    = 0;

    phhalHif_Init(...);

    phhalHif_InitRxBuffer(...);
}

Any clarification would be helpful.

Thanks.

[EduardoZamora]

Hello @uday_gowda

The host interface will sample the value of CTS before sending a byte; CTS must be in valid state for TX to proceed.

Perhaps you can try to "bypass" it by driving it to a fixed ready state. You could consider pulling CTS to the active state by using an external resistor.

Regards,
Eduardo.

[uday_gowda]

Hello @EduardoZamora 

Thank you for the clarification. Your explanation has given me a better understanding of how HSU communication depends on the CTS state before TX proceeds.

I understand the hardware workaround of pulling CTS to the active state externally. Could you please confirm if there is any register/API available to disable CTS dependency completely in software instead of using an external pull-down?

Thanks.