AS5047u SPI Driver

[kavinkumar]

So i started to learn stm32cubeide recently i decided to write a driver for AS5047u magnetic sensor using SPI and i can communicate with the IC with SPI. On reading the data i get a 16 bit value from it the first two bits are don't care bits and i have now 14 bits of data. How do i convert them into angles ? should i convert the 14bit Binary vaue into something else ??? This is the datasheet of the IC
https://look.ams-osram.com/m/48d90c982e0879e8/original/AS5047U-DS000637.pdf
 Any help would be appreciated. Thank you 

[Tesla DeLorean]

Perhaps 360 / 16384 = 0.02197265625

Velocity quoted as 24.141 degrees/second/bit

https://github.com/Adrien-Legrand/AS5X47

https://github.com/Adrien-Legrand/AS5X47/blob/master/src/AS5X47.cpp#L71

https://github.com/jonas-merkle/AS5047P

https://github.com/jonas-merkle/AS5047P/blob/master/src/AS5047P.cpp#L227

[kavinkumar]

Why should i divide it by 16384?

Also the SPI data will be in binary right? what should i divide it with?

[Tesla DeLorean]

Why would you think?  2**14 = 16384

0 ..16383 relates to 0 to 359.99

You're trying to scale the full range 14-bit value into 360 degrees, or 2PI radians

Binary value, multiplied by 0.02197 to scale to degrees

[kavinkumar]

Understood if i want to know the angle i should multiply the binary value by 0.02197 like this 

	  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);
	  HAL_SPI_TransmitReceive(&hspi1, (uint8_t*)&angle_addr, data, 16, HAL_MAX_DELAY);
	  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);
	  uint16_t value = (data[0]<<8) | data[1];
	  angle = value*0.02197.;

[Tesla DeLorean]

>>HAL_SPI_TransmitReceive(&hspi1, (uint8_t*)&angle_addr, data, 16, HAL_MAX_DELAY);

16 bytes? Also doesn't it return the response in a subsequent interaction? It's not going to know the address whilst you're shifting it in. That's what the NOP's for, to clear out the chain of requests.

Would probably mask or check the ER bits

https://look.ams-osram.com/m/48d90c982e0879e8/original/AS5047U-DS000637.pdf

Send a READ ANGLEUNC + NOP sequence as a 4-byte pattern

uint16_t value = ((data[2]<<8) | data[3]) & 0x3FFF;
float angle = (float)value*0.02197f;

[kavinkumar]

sorry i couldn't understand your second statement ERbits you mean the don't care bit rights yeah i changed it afterwards to remove the first two bits

You mean like this 

  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);
	  HAL_SPI_Transmit(&hspi1, (uint8_t*)&ANGLECOM, 16, HAL_MAX_DELAY);
	  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);

	  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);
	  HAL_SPI_TransmitReceive(&hspi1, (uint8_t*)&NOP, data, 16, HAL_MAX_DELAY); 
	  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);

	  uint16_t value = ((data[0]<<8) | data[1]) & 0x3FFF;
	  angle = (float)value*0.02197f;
	  HAL_Delay(250);

  }

[Tesla DeLorean · Accepted solution]

Which part, the one where the document explains you're sending data out, and getting it back later?

That each 16-bit frame has a CS around it, the bus is symmetrical, so you send the read command in one burst, but get the response in the next, and send a new command or NOP.

So Read ADD[ANGLEUNC] then Read ADD[NOP], the data you get back when clocking out the NOP will be the ANGLEUNC value.

[kavinkumar]

is my code in the above reply is correct?

[kavinkumar]

I tried this and i get a value in the range of 0 to 360 degree but the live expressions doesn't seem to be updating