How to write on external IC's registers connected to the SPI2 line of STM32F407VG MCU?

[Lorenzo Estienne]

Posted on December 09, 2017 at 12:46

Hello everybody,

I need to write some registers of an integrated circuit connected to an STM32F407VG MCU by the SPI2 line.

I found these two functions:

     -SPI_I2S_ReceiveData()

     -SPI_I2S_SendData()

which documentation can be found at

http://www.disca.upv.es/aperles/arm_cortex_m3/curset/STM32F4xx_DSP_StdPeriph_Lib_V1.0.1/html/group___s_p_i___group2.html

I just didn't get how to tell the function which register I want to write to, since the SPI_I2S_SendData() accepts only 2 parameters: SPI line number (e.g. SPI1, SPI2, SPI3) and the data to be transmitted.

Any help is highly appreciated.

Thank you,

best regards,

Lorenzo

#register #spi #firmware #data

[waclawek.jan]

Posted on December 09, 2017 at 13:35

Read the external chip's datasheet. It should tell you what data to send in order to write to its registers.

JW

[Andrew Neil · Accepted solution]

Posted on December 09, 2017 at 19:16

Lorenzo Estienne wrote:

I just didn't get how to tell the function which register I want to write to, since the SPI_I2S_SendData() accepts only 2 parameters: SPI line number (e.g. SPI1, SPI2, SPI3) and the data to be transmitted.

That's because SPI has no definition of 'registers' or 'addresses' - it's all just data.

It's only your mystery '

integrated circuit' that assigns meaning to those bytes.

As  ​ (or is it ​) says, you'll have to study the datasheet of your mystery '

integrated circuit'  to find the required format for the data ...

[Lorenzo Estienne]

Posted on December 09, 2017 at 21:43

Thank you both!

I firstly had to use the SPI_I2S_SendData() function to select the register, and THEN use it again to tell the data I wanted to write on the register I previously chosen.

[Lorenzo Estienne]

Posted on December 09, 2017 at 21:54

I've created a function that takes as arguments the SPI line, the register, and the data that I want to write.

Then this function executed the SPI_I2S_SendData() twice.

[Andrew Neil]

Posted on December 09, 2017 at 21:52

are you sure you couldn't do it all in one?