stm32f407vg spi1 data register stay 0xff

[Jalal Sadigli]

Posted on May 02, 2017 at 10:53

hi, i am new to community.....

i have a stm32f4 discovery board with sym32f407cg microcontroller i tried to test spi communucation of the microcontroller with onboard accelerometer

but there is one or more problem that i can not hande

the problem is whatever i write on data register of spi1 , the register only shows 0xff when i read it with the help of pointer

how can i solve this problem

thats what i did as settings of spi1..

spi_cr1 |= 0x30; // select speed

spi_cr1 |= 0x03; // select cpha and cpol spi_cr1 |= 0x00; // select dff spi_cr1 |= 0x00; // select msbfirst

spi_cr2 |= 0x10; // select frf

spi_cr2 |= 0x04; // set ssoe spi_cr1 |= 0x04; // set mstr spi_cr1 |= 0x40; // enable spi##discovery ##spi #stm32

[waclawek.jan]

Posted on May 02, 2017 at 12:28

The SPI_DR is in fact two registers: when you write it, it is the transmit buffer; when you read it, it is the receive buffer. Thus you read always what you've received last.

JW

[Jalal Sadigli]

Posted on May 02, 2017 at 13:13

Thanks for your reply

But the problem is when i write 0x20 to data register ,it shows 0xff on dr

[waclawek.jan]

Posted on May 02, 2017 at 13:29

That's it - you'll never read back the data you've written into SPI_DR, except if you loop back MOSI into MISO externally.

JW

[S.Ma]

Posted on May 02, 2017 at 13:41

Use Cube example for SPI for Nucleo or Discovery of the same STM32Family. Check the schematics that the sensor can be properly addressed as SPI. In some sensors, they power up in SPI 3 wire mode and there might be a bit to write in the sensor to activate the 4 wire mode (for very generic SPI communication).

[Tesla DeLorean]

Posted on May 03, 2017 at 01:16

What version of the board do you have? Which accelerometer does it use?

Is this an official ST board, or a clone?

[Jalal Sadigli]

Posted on May 02, 2017 at 23:52

okay , i have tested shorted miso and mosi that worked . what i had sent over spi returned back and i can saw it .

but when  i try to communicate with accelerometer rx data become 0xff 

i can not handle the problem

[Jalal Sadigli]

Posted on May 02, 2017 at 23:54

i have looked into datasheet of accelerometer there is no such kind of information also tutorials written about onboard accelerometer (stm32f4discovery board) does not contain any that kind of info.

[Jalal Sadigli]

Posted on May 03, 2017 at 10:36

it is probably cloned one because i have bought it from china.

the accelerometer is 

LIS3DSH

how to check version of board?

[Tesla DeLorean]

Posted on May 03, 2017 at 17:28

The colour of the board, buttons, and audio jack should be consistent with this image. The version is in the top corner, the newer boards have ''STM32F407G-DISC1'' silk-screened in the top-left corner, and a board ♯ MB997D