TMS320F28388D: How to read the MISO lines

Hi,

As per the suggestion I tried to read the MISO lines using below API.

SPI_receiveNBytes(mySPI0_BASE, &read_data, 5, 0U);

But the data stored to read_data register is left shifted by one bit. 

Also MOSI line is always zero even though i am sending 0x2100000000 data

Below is the OSCILLOSCOPE image captured while reading the register without API.

Yellow is CLOCK

Blue is MISO

Red is MOSI

Below is the OSCILLOSCOPE image captured while reading the register with API.

On comparing the two images its observed that there is a initial delay in clock. I am curious to know why is this happening. Is this the reason my received data is getting shifting to left by one bit.

Thanks

 Navya Anna Prince

Navya,

SPI_receiveNBytes does transmit 0x00 to initiate the SPI transaction. So, it is not surprising to see you seeing 0's on MOSI.

If you want to transmit / receive 'N' byte simulatanously you need to use

SPI_pollingFIFOTransaction(base, charLength, &TxBuffer, &RxBuffer, numOfWords, txDelay)

where,

base = mySPI0_BASE

charLength = 8U

TXbuffer should be filled with 0x2100000000

RXbuffer can be empty

numOfWords = 5U

txDelay = 0U  

"On comparing the two images its observed that there is a initial delay in clock. I am curious to know why is this happening. Is this the reason my received data is getting shifting to left by one bit."

Are you sure slave and master are working on same clock scheme? I also see lot of ringing noise on the SPI bus. Consider doing impedance matching and clean up your signals

Hi,

As per the suggestion i tried to use  SPI_pollingFIFOTransaction(base, charLength, &TxBuffer, &RxBuffer, numOfWords, txDelay) API to read the MOSI and MISO lines but still getting the same result on the Oscilloscope. Below is the image for the same

Here in MOSI line i am sending 0x2100000000 but not getting the same on the Oscilloscope. 

Below is the code for reading the SPI MISO data

uint32_t SPI_Receive_Multichannel_Motor(uint16_t *address)
{
int i=0;

uint16_t read_data[5] ={0};
uint32_t receivedData=0;

SPI_pollingFIFOTransaction(SPIB_BASE, 8U, address, read_data, 5U, 0U);
SPI_enableFIFO(SPIB_BASE);

return receivedData;

}

And below is the clock scheme for slave and master

Navya,

Navya Anna Prince said:

Here in MOSI line i am sending 0x2100000000 but not getting the same on the Oscilloscope. 

I'm really concerned with the amount ringing noise of SPI bus. The ringing noise is high enough to cause communication error. That is the reason why I suggested you perform impedance matching.

Can you just try transmitting a byte and check whether you correctly see 0x21 transmitted in both the methods shown below

Method1: SPI_transmitByte(SPIB_BASE, 0x21);

Method2:

temp = 0x21;

addr = &temp;

SPI_pollingFIFOTransaction(SPIB_BASE, 8U, address, read_data, 1U, 0U);

Can you show me how you are packing the address in 0x2100000000? This is how I would package the data. Is this how you are doing?

TxData_SPIB[0] = 0x21;

TxData_SPIB[1] = 0x00;

TxData_SPIB[2] = 0x00;

TxData_SPIB[3] = 0x00;

TxData_SPIB[4] = 0x00;

address = &TxData_SPIB[0]

Regards,

Manoj

Also, which SPI slave are you trying to communicate?

Hello,

which SPI slave are you trying to communicate?

We are trying to connect to TMC5160A motor driver via SPI with TMS320F28388D controller

Below is the SPI configuration needed for communication

• SPI Speed : 1Mhz
• SPI Mode : 3
• SPI character length : 8
• Motor driver register length : 40(8 bit address + 32 bit Data)
• We have to send send 8 bits five times as motor driver register needs 40 bits of data.

//SPIB GPIO Configuration
SysCtl_enablePeripheral(SYSCTL_PERIPH_CLK_SPIB);
GPIO_setPinConfig(GPIO_24_SPIB_SIMO);
GPIO_setPinConfig(GPIO_25_SPIB_SOMI);
GPIO_setPinConfig(GPIO_26_SPIB_CLK);
GPIO_setPinConfig(GPIO_27_SPIB_STEN);

//mySPIB initialization
SPI_disableModule(SPIB_BASE);
SPI_enableFIFO(SPIB_BASE);
SPI_setConfig(SPIB_BASE, DEVICE_LSPCLK_FREQ, SPI_PROT_POL1PHA0,
SPI_MODE_MASTER, 1000000, 8);
SPI_disableLoopback(SPIB_BASE);
SPI_enableTalk(SPIB_BASE);
SPI_disableInterrupt(SPIB_BASE, SPI_INT_TXFF);
SPI_setEmulationMode(SPIB_BASE, SPI_EMULATION_FREE_RUN);
SPI_enableModule(SPIB_BASE);

Method1: SPI_transmitByte(SPIB_BASE, 0x21);

While trying method 1, code is not going to next line of execution . I am guessing since I have enable FIFO in my SPI Configuration its not going to next line.

Method2:

temp = 0x21;

addr = &temp;

SPI_pollingFIFOTransaction(SPIB_BASE, 8U, address, read_data, 1U, 0U);

Above is the Oscilloscope image for sending 8 bits with SPI_pollingFIFOTransaction(SPIB_BASE, 8U, address, read_data, 1U, 0U);

Can you show me how you are packing the address in 0x2100000000? 

uint32_t Get_Motor_Register_X(uint16_t Address)
{
uint16_t *SPI_Data=0;
uint32_t received_data=0;
SPI_Data[0]=Address;
SPI_Data[1]=0;
SPI_Data[2]=0;
SPI_Data[3]=0;
SPI_Data[4]=0;
received_data= SPI_Receive_X_Motor(SPI_Data); //Here i am calling the API for SPI Transmit and SPI Response
;

return received_data;

}

The ringing noise is high enough to cause communication error. That is the reason why I suggested you perform impedance matching.

i am sorry i didn't understand by impedance matching. Could you elaborate a little on this?

Thanks

Navya

Navya Anna Prince said:

Method1: SPI_transmitByte(SPIB_BASE, 0x21);

While trying method 1, code is not going to next line of execution . I am guessing since I have enable FIFO in my SPI Configuration its not going to next line.

I see you have configured SPI chip select pin as SPI pin and not GPIO pin. You need to configure SPI chip select pin as GPIO output pin and do the following. When you mentioned the code was stuck, it should have stuck in SPI_writeDataBlockingNonFIFO function waiting for the transmission to complete.

Also, don't enable the SPI FIFO when you use SPI_transmitByte function

You can check spi_ex6_eeprom (C2000Ware example), this shows how the how these driver lib APIs are used.

1) Pull GPIO (used for chipselect) LOW

2) SPI_transmitByte(SPIB_BASE, 0x21)

Navya Anna Prince said:

The ringing noise is high enough to cause communication error. That is the reason why I suggested you perform impedance matching.

i am sorry i didn't understand by impedance matching. Could you elaborate a little on this?

This is a basic electrical engineering topic and taken care during the pcb design. There is lot of material online when search for impedance matching. Ringing noise I see on your SPI bus (spikes on SPI signals) can lead to communication issues.

From TI, we have this appnote which covers this topic with respect to SDFM peripheral but the concepts are universal and can be applied to SPI

Achieving Better Signal Integrity With Isolated Delta-Sigma Modulators in Motor Drives (https://www.ti.com/lit/tida033)

Regards,

Manoj