Posted on May 17, 2011 at 09:40Hi
has anyone solved the loop back problem in SSP?
when the ssp is used in the master mode and data is transmitted on the mosi pin and received on miso pin. transmitted data is correct but the received data is just the copy of transmitted data.
The nss pin is directly connected to the LRC (left right clock) of codec without any pull up resistor. when data that comes on the miso pin is seen in an oscilloscope it is not the transmitted data. the loop back happens inside the microcontroller.
Connecting the nss pin to vcc is not an option for me as the ssp is configured in SSI mode to communicate with a codec.
the code is as follow:
void SSPCodec_Init(void)
{
SSP_InitTypeDef SSP_InitStructure;
// SSP1 configuration
SSP_DeInit(SSP1);
SSP_InitStructure.SSP_FrameFormat = SSP_FrameFormat_TI;
SSP_InitStructure.SSP_Mode = SSP_Mode_Master;
SSP_InitStructure.SSP_CPOL = SSP_CPOL_High;
SSP_InitStructure.SSP_CPHA = SSP_CPHA_1Edge;
SSP_InitStructure.SSP_DataSize = SSP_DataSize_8b;
SSP_InitStructure.SSP_ClockRate = 0; //5- for slave; 0-for master
SSP_InitStructure.SSP_ClockPrescaler = 24;
SSP_Init(SSP1, &SSP_InitStructure);
// Disable the Loop back mode for the SSP1 peripheral
SSP_LoopBackConfig(SSP1, DISABLE);
// SSP1 enable
SSP_Cmd(SSP1, ENABLE);
}
int main(void)
{
u8 cnt=0;
.........
while(1)
{
if(send_ready==1)//wait for 1/48kHz duration, flag is set in tim2 ISR
{
send_ready=0; //reset flag
SSP_SendData(SSP1, sin_data[cnt]);
//wait to receive data
while(SSP_GetFlagStatus(SSP1, SSP_FLAG_RxFifoNotEmpty) == RESET);
mic_data[cnt] = SSP_ReceiveData(SSP1); //Receive the output of mic
cnt++;
if (cnt == NbrOfSamples)
{
cnt = 0;
}
}
}
}
Please, help me out.
Thanks in advance,
vik
