[DONE]SPI Daisy chain with MPU-9250

Projects Networking, Protocols, and Devices
1

Hi
I use an Arduino Due and try to communicate with two MPU-9250 with daisy chain.
I wired it like this:
MOSI -> SDI 1
SDO 1 -> SDI 2
SDO 2 -> MISO

Same GND, VCC and CS

I now like to get the temperature (register 0x41 tempH, register 0x42 tempL).

I programmed the following code to first get the values in tempH and then tempL.

Issue is it doesn't work. I connected a logic analyzer to the MISO and MOSI pins from the Due but it's not what I expected (tempH have to be 0x03, and in daisy chain twice).

So can anybody help me here?

void setup() {
  Serial.begin(9600);

  pinMode(csPin,OUTPUT);
  digitalWrite(csPin,HIGH);
  SPI.begin();
  mpuConfigure();
}

void loop() {
  // high register
  SPI.beginTransaction(SPISettings(SPIclk, MSBFIRST, SPI_MODE3));
  digitalWrite(csPin,LOW);
  
  SPI.transfer(0x41 | 0x80);
  buffer[0] = SPI.transfer(0x41 | 0x80);
  buffer[1] = SPI.transfer(0x41 | 0x80);
  
  digitalWrite(csPin, HIGH);
  SPI.endTransaction();

  delayMicroseconds(10);

  // low register
  SPI.beginTransaction(SPISettings(SPIclk, MSBFIRST, SPI_MODE3));
  digitalWrite(csPin,LOW);
  
  SPI.transfer(0x42 | 0x80);
  buffer[2] = SPI.transfer(0x42 | 0x80);
  buffer[3] = SPI.transfer(0x42 | 0x80);
  
  digitalWrite(csPin, HIGH);
  SPI.endTransaction();
  
  // calculation
  tempCache1 = ((int16_t)buffer[0] << 8) | buffer[2];
  tempCache2 = ((int16_t)buffer[1] << 8) | buffer[3];

  tempC1 = ((tempCache1 - 21.0) / 333.87) + 21.0;
  tempC2 = ((tempCache2 - 21.0) / 333.87) + 21.0;   

  // output
  Serial.print("MPU 1: ");
  Serial.println(tempCache1);
  Serial.println(tempC1);
  Serial.print("MPU 2: ");
  Serial.println(tempCache2);
  Serial.println(tempC2);
}

SPI_daisy_chain.png
SPI_daisy_chain.png825×341 6.17 KB

2

a_n:
Hi
I use an Arduino Due and try to communicate with two MPU-9250 with daisy chain.
I wired it like this:
MOSI -> SDI 1
SDO 1 -> SDI 2
SDO 2 -> MISO

Same GND, VCC and CS

Where did you see that you can daisy chain those?!! unless there there is some kind of SPI port 'IN' and SPI port 'OUT' on SPI devices, generally daisy chaining is NOT possible.

you would need to use seperate CS pins for each MPU-9250 to get the correct response from either of them.
Capture.PNG

Hope that helps....

Capture.PNG

3

sherzaad:
Where did you see that you can daisy chain those?!! unless there there is some kind of SPI port 'IN' and SPI port 'OUT' on SPI devices, generally daisy chaining is NOT possible.

So not every chip which can SPI support daisy chain?
Thought when they deliver the same data length it is allright.

Then you can say, if it's not written in the datasheet it's not possible.

Ok, thanks.