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I am currently using an eZdsp F2812 evaluation board and trying to get the serial communications interface (SCI) to work. I have configured the SCI for 9600 Baud, 8 data bits, 1 stop bit, and parity none (as shown in the InitSerialPort function below). The Development Environment is Code Composer Suite v7 (7.3.0).
void InitSerialPort(void)
{
int baudRateRegister = 0;
/* Channel A Setup */
SciaRegs.SCICCR.all = 0x0007; // 8 data bits, 1 stop bit, parity-none
SciaRegs.SCICTL1.all = 0x0043; // enable TX, RX, internal SCICLK, Disable RX ERR, SLEEP, TXWAKE
SciaRegs.SCICTL2.bit.TXINTENA = 0; // No tx interrupt
SciaRegs.SCICTL2.bit.RXBKINTENA = 0; // No rx interrupt
baudRateRegister = 37500000/(8 * 9600) - 1;
SciaRegs.SCIHBAUD = (baudRateRegister & 0xFF00) >> 8;
SciaRegs.SCILBAUD = baudRateRegister & 0x00FF;
SciaRegs.SCIFFTX.all=0xC001; // Int when 1 byte left (disabled)
SciaRegs.SCIFFRX.all=0x002F; // Int when 15 bytes present
SciaRegs.SCIFFCT.all=0x0000;
SciaRegs.SCICTL1.all =0x0063; // Relinquish SCI from Reset
SciaRegs.SCIFFTX.bit.TXFIFOXRESET=1;
SciaRegs.SCIFFRX.bit.RXFIFORESET=1;
} /* InitSerialPort */
Using the eval board, I’ve connected the SCITXDA (P8-3)/SCIRXDA (P8-4) pins to the TxD/RxD pins on my RS232-to-USB adapter. The ground on the adapter is connected to P8-19 (Analog Ground). The RS232-to-USB adapter is connected to my laptop where I’m running a PuTTY client. I’m assuming the communications standard is RS-232.
After calling the InitSerialPort (along with the other DSP Initialization routines), I call the ReportResults function, which is continuously outputting the character ‘A’.
void ReportResults(void)
{
char transmitBuffer[TRANSMIT_BUFFER_BYTE_LENGTH] = {0};
int characterCount = 0;
sprintf(transmitBuffer, "A");
characterCount = strlen(transmitBuffer);
SendBuffer(SERIAL_PORT_A, transmitBuffer, characterCount);
} /* ReportResults */
In order for the ‘A’ character to be displayed in PuTTY, I must modify the character’s ASCII value by left-shifting by one bit and then inverting the shifted value. This is accomplished in the ModCharacter function, which is called by SendBuffer.
int SendBuffer(char portSelection, char *buffer, Uint16 bufferByteCount)
{
int index;
int count = 0;
for (index=0; index < bufferByteCount; index++)
{
SciaRegs.SCITXBUF = ModCharacter(buffer[index] & 0x00FF);
while (SciaRegs.SCICTL2.bit.TXRDY != 1);
count++;
}
// return bytes accepted
return count;
} /* SendBuffer */
char ModCharacter(char character)
{
char tempCharacter = character << 1;
return (~tempCharacter);
} /* ModCharacter */
I’ve attached the screen shot from the scope of the ‘A’ character on the TxD pin. My question is why do I need to bit-shift and invert the data?
When I try to send data to the eZdsp eval card, then the communications is in the correct Start-Data-Stop-Bit order and not understood by the UART. I receive an RxError from the UART as expected. If I could invert the data and then right-shift the it by one bit, then it might work.
I forgot to attach the screen captures from the scope in the initial report. I’ve attached new captures under two different cases. In the first case, I’m outputting 0x00 continuously and receiving 0xFF in the log file that is captured using PuTTY. (I have PuTTY to capture All Session Output.) The associated screen capture is named, “FFs in PuTTY.png”. In the second case, I’m outputting 0xFF continuously and receiving 0x00 in the PuTTY log file. The associated scope capture is named, “00s in PuTTY.png”.
