SPI Receive problem

Question

Posted on June 27, 2017 at 06:45Hi all,I am trying to read a four bytes register from TDC-GP30 ultrasonic flow converter using HAL_SPI_Receive function. Below is the code that I am using for reading the register contents:/******************************************************************************* * Function Name: gp30_read_n_bytes * Parameters: n_bytes = how many bytes should be read * read_opcode = read opcode of the device * read_addr = read address of the device * * Return: n bytes from the specified read address * * Description: Reads n bytes from an address in GP30 * ******************************************************************************/float gp30_read_4_bytes(uint8_t read_opcode, uint8_t read_addr){ uint32_t Result_read = 0x00000000; uint8_t Result_read_buff = 0x00;  GP30_SPI_enable();  HAL_SPI_Transmit(&hspi1,&read_opcode,1,100); HAL_SPI_Transmit(&hspi1,&read_addr,1,100);   HAL_SPI_Receive(&hspi1,&Result_read_buff,1,100); Result_read |= (Result_read_buff<<24);  HAL_SPI_Receive(&hspi1,&Result_read_buff,1,100); Result_read |= (Result_read_buff<<16);  HAL_SPI_Receive(&hspi1,&Result_read_buff,1,100); Result_read |= (Result_read_buff<<8);  HAL_SPI_Receive(&hspi1,&Result_read_buff,1,100); Result_read |= (Result_read_buff);  GP30_SPI_disable();  return Result_read;}The problem is that I cannot receive all four bytes. For example one register contains 0x12345678 and when I read its content I receive 0x12345600 all the time. Its receiving fine for some other values but not for all values.

hashem ahmadi · Accepted Answer

Posted on July 02, 2017 at 19:27Well my problem become solved simply by changing the input type from float to uint32_t.

Mathew Hystek · Answer

Posted on July 02, 2017 at 12:15Hi HashemI am having problems too, all though I dont have a full understanding of it.But I would imagine how it works is as follows:https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2(SPI_HandleTypeDef *hspi, uint8_t *pData, uint16_t Size, uint32_t Timeout)When you use https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2, the clock pin outputs based on the size of the data (hspi1.Init.DataSize) and the https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2 multiplier parameter (which is the third parameter, uint16_t Size)If your hspi1.Init.DataSize is set to 10bit, and the multiplier is set to 1, then the clock pin will output 10 times.If the multiplier is set to 2, then the clock pin will output 20 timesHowever the https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2 parameter (uint8_t *pData) will only transmit on the first 10 bits.Here I am sending 0xF, 10bit data size, 2 x multiplierbased on the datasheet of the device i am talking to, I cannot use 2 x multiplier. Why? because it will send data during https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2. And to my understanding, https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2 is non blocking mode, which means the application waits for https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2 to finish before proceeding with the rest of the program/application.So I would image I would use https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#ga02ec86e05d0702387c221f90b6f041a2 with a multiplier of 1, where the clock sends 10 bits.Then I would use https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#gafdf43dbe4e5ef225bed6650b6e8c6313 with also a multiplier of 1, causing the clock to sen additional 10bits and also listening on the MISO line.But what actually happens when you use https://developer.mbed.org/users/EricLew/code/STM32L4xx_HAL_Driver/docs/tip/group__SPI__Exported__Functions__Group2.html#gafdf43dbe4e5ef225bed6650b6e8c6313, it does not send any additional bits on the clock (otherwise i would see it on the oscilloscope) and instead goes to some sort of infinite loop called HardFault_HandlerWhy? this is the third device in a row I have used that has the exact same problem with SPI under the STM32 family.the varibles I am using: uint8_t SpiTransmit = 0xF; uint8_t SpiReceive;calling the HAL functions in main while(1) HAL_SPI_Transmit(&hspi1, &SpiTransmit, 1, 10); HAL_SPI_Receive(&hspi1, &SpiReceive, 1, 10);HAL_Delay(100);initiation code generated from STM32CubeMX 4.19compiled using Keil uVision v5.23

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