BMA456 Simple read of Acceleration Values

[HBUDE]

Hello,

we are using BMA456, connected to a uC via SPI Interface.

In first step, I simply want to read the acceleration data registers, and I wrote a small program according to the steps described in "Example 2" of the data sheet.

But the readout of the registers is always Zero.

What am I doing wrong, resp. what do I have to do to make it work ? Is there any further initialisation/configuration necessary ? If so, does anybody have a code example for this ?

I downloaded the driver API, but there is a lot of code inside which I do not (yet) understand.

I searched the net carefully, but could not find any help or information....

Thanks in advance, bye

Harald

[HBUDE]

Hello again,

I migrated the acceleration example project to my hardware, but unfortunately it does not work correctly...

I can see that in lines 921+922 of module bma4.c:

 rslt = bma4_read_regs(BMA4_INTERNAL_STAT, &config_stream_status, 1, dev);
config_stream_status = config_stream_status & BMA4_CONFIG_STREAM_MESSAGE_MSK;

the content of variable config_stream_status is 0 after execution of function bma4_read_regs(...). This seems to signal an error.

Sorry, but I do not exactly understand what this function does, but I believe it could be a problem of my implementation of functions user_spi_read(...) and

user_spi_write(...).

I implemented the following code by use of HAL SPI functions. Could you please check if there is something wrong ?

I assume the code in user_spi_write() is possibly not correct. On call of the function I first transmit one byte of adress data, after the register data with given length. Is that okay ?!

/*!
* @brief Function for writing the sensor's registers through SPI bus.
*/
int8_t user_spi_write(uint8_t reg_addr, const uint8_t *reg_data, uint32_t length, void *intf_ptr)
{

/* Implement the SPI write routine according to the target machine. */

HAL_GPIO_WritePin(SPI2_ACC_NSS_GPIO_Port,SPI2_ACC_NSS_Pin,GPIO_PIN_RESET); // NSS Pin = Low

HAL_SPI_Transmit(&hspi2,&reg_addr,1,100); // Transmit Register Adress
HAL_SPI_Transmit(&hspi2,(uint8_t *)reg_data,length,100); // Transmit Data

HAL_GPIO_WritePin(SPI2_ACC_NSS_GPIO_Port,SPI2_ACC_NSS_Pin,GPIO_PIN_SET); // NSS Pin = High

return 0;
}

/*!
* @brief Function for reading the sensor's registers through SPI bus.
*/

int8_t user_spi_read(uint8_t reg_addr, uint8_t *reg_data, uint32_t length, void *intf_ptr)
{

/* Implement the SPI read routine according to the target machine. */

HAL_GPIO_WritePin(SPI2_ACC_NSS_GPIO_Port,SPI2_ACC_NSS_Pin,GPIO_PIN_RESET); // NSS Pin = Low

HAL_SPI_TransmitReceive(&hspi2,&reg_addr,reg_data,length,100);

HAL_GPIO_WritePin(SPI2_ACC_NSS_GPIO_Port,SPI2_ACC_NSS_Pin,GPIO_PIN_SET); // NSS Pin = High

return 0;
}

Thank you in advance, kind regards

Harald

[HBUDE]

Hello again,

it's okay now, I found the problem. The use of HAL_SPI_TransmitReceive in function user_spi_read() was wrong. I replaced it by

HAL_SPI_Transmit(&hspi2,&reg_addr,1,100); // Transmit Register Adress
HAL_SPI_Receive(&hspi2,reg_data,length,100); // Receive Register Data

and now it works....it seems, the second dummy write byte of adress transfer is included in the receive data length, or not ?

However, now it works and that's great 🙂

Thanks a lot for your assistance

Harald

[BSTRobin]

Hello HBUDE,

HAL_SPI_TransmitReceive() also could work. You could refer example code I uploaded in another ticket: https://community.bosch-sensortec.com/t5/MEMS-sensors-forum/BMA456-Init-fail/m-p/47081#M8520

[HBUDE · Accepted solution]

Hello BSTRobin,

thanks for information. I know it's working, I simply used the wrong data length in this function.

Thanks again, bye

Harald