STM32H7 SPI clock frequency, is not changing with different BaudratePrescaler Value

0
votes

my SPI kernel clock at 400Mhz and prescaler 256 at this configuration alone, my SPI is generating Clk, MISO,MOSI, CS signals, when I change the Prescaler Value other than this value, none of the signals are generated, the code enters into a Loop, Device busy status is returning.

With this configuration, only 1.56Mhz SPI clk speed is running. I want to increase the SPI clk speed. Pls help me out.

My SPI Init is as follows:

hspi1.Instance = SPI1;
hspi1.Init.Mode = SPI_MODE_MASTER;
hspi1.Init.Direction = SPI_DIRECTION_2LINES;
hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;
hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;
hspi1.Init.NSS = SPI_NSS_SOFT;
//hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_8;
hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
hspi1.Init.CRCPolynomial = 7;
hspi1.Init.NSSPMode = SPI_NSS_PULSE_ENABLE;

I want to execute the SPI clk at 80 or 100 Mhz which is the max execution speed of SPI in STM32.

1
cembedded
Are you aware of all the tough requirements that the hardware needs to fulfil in order to run SPI that fast? Why do you need such extreme speeds? – Lundin
Thank you Lundin, I am using SPI NOR Flash. Its normal read/write can be done at 80Mhz. My filesystem LittleFS gets executes properly sometimes, and most of the time device busy status occurs. hence thought of increasing the clk. – Indu
Have you configured proper slew rate settings (IO speed settings) for the GPIOs that you use as output pins? – th33lf
@Lundin, I was able to do SPI communication between two STM32H7 Nucleo boards connected with basic wires at around 100MHz. Could you elaborate on the touch requirements you are mentioning ? – Guillaume Petitjean
Thank you @ Guillaume Petitjean and @th33lf. Changed the speed to Very high, it worked. – Indu

1 Answers

2
votes

I've had the exact same issue and it was due to the GPIO output speed setting. You should check and change it to Very High Speed (register GPIOx_OSPEEDR).