XON / XOFF uart flow control

[sethu_jangala]

Hi everybody,

I'm working with a project that needs to transfer higth speed serial data from a XMOS device to a HOST PC.

I used the modules fast uart (https://github.com/xcore/sc_uart) prensent in gihub repository.

I want to implement a serial XON/XOFF software flow control to transfer data from XMOS device to a host PC.

I wrote the following code, but seems doesn't work well.


//Send buffer data to UART
void SendToSerial(streaming chanend DataFromFIFO, streaming chanend DataFromHostPC, streaming chanend DataToHostPC) {
    unsigned int     rx;
    unsigned char  XON = 1;
    unsigned char     RxFlow;    
    
    while(1){
        select {
        // xon/xoff char received from PC
        case DataFromHostPC:> RxFlow:

            if ( RxFlow == XOFF_CHAR){
                XON = 0;
            }
            if ( RxFlow == XON_CHAR ){
                XON = 1;

            }
            break;
            
        // data from fifo to be sent over uart to the host pc
        case DataFromFIFO :> rx:

                // Checking if the transmission must be stopped
                while( XON == 0 ){
                    DataFromHostPC:>RxFlow; // wait PC command

                    if ( RxFlow == XON_CHAR ){
                        XON = 1;
                    }

                }        // wating xon char ok

                DataToHostPC <: rx;
                break;


        }
    }

}

In main, i have:

    par {
        GetFromFIFO(DataFromFIFO);                                        //  Get data from fifo
        HandleUart(DataFromFIFO,DataFromHostPC,DataToHostPC);            //     Send data to UART
        ReceiveXOFF(DataFromHostPC);                                    // Get data received from PC via UART
        SendToHost(DataToHostPC);                                        //     Send data to UART
    }

 

Checking the serial lines with the oscilloscope, when the XOFF char is sent by the host pc, the data doesn't stops. Where is the problem?

How to proper implement xon/xoff software flow control? Is there any sample code?

Thanks in advance.

 

 

 
 
Read

[sethu_jangala]

Try changing streaming channels to normal channels and see if this solves your issue. Can you export and send the workspace if possible?

[fdaniii]

Try changing streaming channels to normal channels and see if this solves your issue. Can you export and send the workspace if possible?

Thanks for your replay.

The uart fast library has a prototype that takes as input a streaming channel:

Code: Select all

void uart_rx_fast(in port p, streaming chanend c, int clocks);

i need to change the library...

In this case what is the difference between streaming channel and channel??

[sethu_jangala]

The uart fast library has a prototype that takes as input a streaming channel:

Code: Select all

void uart_rx_fast(in port p, streaming chanend c, int clocks);

i need to change the library...

In this case what is the difference between streaming channel and channel??

If the module uses streaming channel you have to use streaming channel in the application. You can find information regarding the difference between streaming channel and normal channel from the following link:
http://www.xcore.com/questions/1778/how ... al-channel

Sethu.