SPI interface of lmp90100 with arduino...

Hi Mike,
I prepared an arduino code according to demo-app01. But it returns value 512 all the time as reg_read _data though reg_write_data is 86.
I changed reg_write_data to another value but it still gives 512 as the reg_read _data . My arduino code is bellow.
#include <SPI.h>
const int chipSelectPin = 42;
void setup() {
int prev_URA; // Previous Upper Register Address (URA)
int reg_write_data, reg_read_data;

Serial.begin(9600);
// start the SPI library:
SPI.begin();
// initalize the data ready and chip select pins:
pinMode(chipSelectPin, OUTPUT);

prev_URA =0XFF;
reg_write_data = 0x56;
TI_LMP90100_SPIWriteReg(0x11, reg_write_data,&prev_URA);
reg_read_data = TI_LMP90100_SPIReadReg(0x11,&prev_URA);
Serial.println("Write_data");
Serial.println(reg_write_data);
Serial.println(reg_read_data);

}

void loop() {
// int reg_write_data, reg_read_data;
// int prev_URA;
// prev_URA =0XFF;
// reg_read_data = TI_LMP90100_SPIReadReg(0x11,&prev_URA);
// if (reg_read_data)
// Serial.println(reg_read_data);

// put your main code here, to run repeatedly:

}


void TI_LMP90100_SPIWriteReg(int addr, int value, int *pURA)
{
int new_URA, inst;

new_URA = (addr & 0x70)>>4; // extract upper register address
Serial.println("SpiWrite");
digitalWrite(chipSelectPin, LOW);
if (*pURA != new_URA) // if new and previous URA not same, add transaction 1
{
inst = 0x10;
SPI.transfer(inst);
delay(10);
SPI.transfer(new_URA);
delay(10);
*pURA = new_URA;
}
inst = 0x00 | 0x00 |(addr & 0x0F); // lower register address
SPI.transfer(inst);
delay(10);
SPI.transfer(value);
delay(10);
digitalWrite(chipSelectPin, HIGH);
}

int TI_LMP90100_SPIReadReg(int addr, int *pURA)
{
int x, new_URA, inst;

new_URA = (addr & 0x70)>>4; // extract upper register address
digitalWrite(chipSelectPin, LOW);
if (*pURA != new_URA) // if new and previous URA not same, add transaction 1
{
inst = 0x10;
SPI.transfer(inst);
delay(10);
SPI.transfer(new_URA);
delay(10);
*pURA = new_URA;
}
inst = 0x80 |0x00 | (addr & 0x0F);
SPI.transfer(inst);
delay(10);
inst=0x00;
while(!x)
x=SPI.transfer(inst);
delay(100);
Serial.println("SpiRead");
Serial.println(x);
delay(100);
digitalWrite(chipSelectPin, HIGH);
return x;
}

Hello,

Yes, you can connect your SPI signals directly to J8.

Mike

Hi Sathish,

If you are using the topology in Figure 78 you can only connect one RTD.  You would need another two current sources to be able to connect another RTD.  Another possibility is to use a device to switch to connect the current sources to one or the other of the RTDs, if you want to use two of them in the Figure 78 topology.

Yes, you can leave RCOMP out.  It is used to set the Vin to be0V at any temperature.

Mike

Hello Charanraj,

Start off by checking that all connections are being properly made to the LMP90100. Do you have power and ground at the pins of the part? Check right at the part. Are your SPI signals also present at the pins of the part? Check your SPI signals with an oscilloscope. Do they match Figure 1 in the datasheet? Are all the timing specifications being met? What data do you see on the SDO pin when you send your write and read sequence?

Mike