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What is the difference between SPI chip select and SPI Pin select?
Also, we were trying to send three 8-bit data from the TMS570LC43x board to a daughter Board. The requirements are that the CS should be low throughout this operation. We are writing a value to a specific register and after that reading the same value from that register. There is transmit operation which takes uses 3 spiTransmit() API. Also in another function, there are 2 spiTransmit() API followed by a spiReceive() API. The code for the same is given below.
Transmit operation:
dataconfig1_t.CS_HOLD = TRUE;
dataconfig1_t.WDEL = FALSE;
dataconfig1_t.DFSEL = SPI_FMT_0;
dataconfig1_t.CSNR = SPI_CS_0;
dataconfig1_f.CS_HOLD = FALSE;
dataconfig1_f.WDEL = FALSE;
dataconfig1_f.DFSEL = SPI_FMT_0;
dataconfig1_f.CSNR = SPI_CS_0;
ack= spiTransmitData((spiBASE_t *)spiREG1,(spiDAT1_t *)&dataconfig1_t,1,(uint16 *)&op1);
ack1=spiTransmitData((spiBASE_t *)spiREG1,(spiDAT1_t *)&dataconfig1_t,1,(uint16 *)&op2);
spiTransmitData((spiBASE_t *)spiREG1,(spiDAT1_t *)&dataconfig1_f,1,(uint16 *)&value);
Receive Operation:
dataconfig1_t.CS_HOLD = TRUE;
dataconfig1_t.WDEL = FALSE;
dataconfig1_t.DFSEL = SPI_FMT_0;
dataconfig1_t.CSNR = SPI_CS_0;
dataconfig1_f.CS_HOLD = FALSE;
dataconfig1_f.WDEL = FALSE;
dataconfig1_f.DFSEL = SPI_FMT_0;
dataconfig1_f.CSNR = SPI_CS_0;
flag1=spiTransmitData((spiBASE_t *)spiREG1,(spiDAT1_t *)&dataconfig1_t,1,(uint16 *)&opcode1);
flag2=spiTransmitData((spiBASE_t *)spiREG1,(spiDAT1_t *)&dataconfig1_t,1,(uint16 *)&opcode2);
flag3=spiReceiveData((spiBASE_t *)spiREG1,(spiDAT1_t *)&dataconfig1_f,1,(uint16 *)&received_data);
The value which we are sending is 0x31 but what we are getting is 00. Can anyone help explain this?
Thanks in advance!
Hi Varikoti,
What is the difference between SPI chip select and SPI Pin select?
spiPinSelect:
Actually, SPI pins can also be operated as GIO, i mean we can SET or RESET the SPI pins values by making them as GIO output and similarly we can also make them as GIO input and can read the SPI pin values. The SPI "spiPinSelect" structure will be used in this case only.
For example, you can see the SPIPC3 register, once you configure any particular SPI pin into GIO output then you can use this register to SET or REST the output.
You can compare the "spiPinSelect" structure with above bit placements, they will match each other.
For example you can also see the above pic, in this example it try to control the output values of few SPI pins and here i used the values of "spiPinSelect" enum structure.
spiChipSelect:
This structure is used to activate the particular chip select pin during the SPI data transfer.
If you refer the "CSNR" field of the SPIDAT1 register, there it is explained about how to enable the particular chip select pin.
For example, if i want to activate the CS0 to low while transferring the data i have to write CSNR value to the 0xFE(SPI_CS_0), like as shown below:
The above code makes the only CS0 active low and other CS pins to active high while transferring the data.
You can also refer below thread for more details:
And here is the example SPI master code for TMS570LC4357:
5224.SPI_MASTER_TEST_LC4357.zip
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Thanks & regards,
Jagadish.
