SCI works fine in loopback mode but in normal mode it doesn't

[Sailesh]

We implemented a SCI for TMS320F28835 TI microcontroller.
In loopback mode SCI working properly but when in normal mode it doesn't trigger receive
interrupt and even oscilloscope also not showing any signal on SCITx pin.

Micro controller supports 3 SCI for testing purpose we made connected SCI-B TX to
SCI-C Rx( Implemented device driver in which SCI-B will be sending some data and
SCI-C suppose to receive).

SCI-B TxINT is getting trigger when we sends but SCI-C RxINT doesnot triggering.
Even TXGpio also not showing of signal in oscilloscope.
SCI code is attached with post

Need help please reply if you have any idea about problem.

 

[Amar Dhore]

1. In your code, Where are you enabling RX and TX.
2. what is your Baud Rate?

May be instead of trying interrupt mode, you should try first with polling, then go from there to interrupt mode.

This might be a helpful document: http://www.ti.com/lit/ug/sprufz5a/sprufz5a.pdf

 

[Sailesh]

Thanks Amar.

I used same pdf for implementing and its not working polling also I tried which is not working.
Baud rate 100K . BRR as 30

Do we have some range of Baud rate for SCI ?

 

[Amar Dhore]

I am confused about your baud rate calc. Note that your Baud rate formula are applicable only when 1 ≤ BRR ≤ 65535. So make sure your baud rate calc is correct.

What is your CPU_FREQ? I do not follow CPU_FREQ 100E6 (100K?)

Helpful link:
https://github.com/jbonaldo/Maquina_Solda/blob/master/Jakson_Bibliotecas/J_SciA_Protocolo_21_02_10.c

 

[Sailesh]

I am trying with 115200 baud rate and BRR is 26. CPU freq 100MHZ.

Sorry in hurry and tension I have written wrong

 

[Sailesh]

I changed baud rate to 9600 and BRR is 0x144. CPU freq 100MHZ.

I tried with SCI adapter which connect with system's hyper terminal.
Ones I tried with RX INT and once polling but nothing is working.

I don't know whats going wrong ?

 

[Amar Dhore]

in here:
void SciA_Transmit(int data)
{
while (SciaRegs.SCIFFTX.bit.TXFFST != 0) {} //Why are you doing this??

// Check if TXRDY is high
SciaRegs.SCITXBUF=data;
//wait for TXRDY to go low

}



Few more things:
1. Enable TXENA
2. Write to SCITXBUF, then the transmitter is no longer empty, and check if TXRDY goes low.
3. If TXRDY goes low, then transmission w2as successful, you can transmit the next byte.
4. I am not sure if yo have to set TXWAKE before you Transmit. Check the specs.

 

[Sailesh]

Thanking you for great support.

Problem was EALLOW was needed for GPIOs

like below:

void Gpio_SciA_init(void)
{
EALLOW;
GpioCtrlRegs.GPBPUD.bit.GPIO35 = 0; // Enable pull-up for GPIO22 (SCITXDA)
GpioCtrlRegs.GPAPUD.bit.GPIO28 = 0; // Enable pull-up for GPIO23 (SCIRXDA)

GpioCtrlRegs.GPAQSEL2.bit.GPIO28 = 3; // Asynch input GPIO23 (SCIRXDA)

GpioCtrlRegs.GPBMUX1.bit.GPIO35 = 1; // Configure GPIO29 for SCITXDA operation
GpioCtrlRegs.GPAMUX2.bit.GPIO28 = 1; // Configure GPIO28 for SCIRXDA operation
EDIS;
}

 

[Amar Dhore]

Great....Glad its working now..