STM32L496 SPI MOSI is wrong at clock 10mhz

[glin00]

Hello,

Description:
I am using ST MCU SPI-1 i/f to connect to OLED display. When I configure Zephyr SPI clock to 5mhz, the OLED displays correctly. But when I configure Zephyr SPI clock to 10mhz, the OLED displays incorrectly. After I use an osilloscope to measure SPI mosi and clock pin, I found SPI clock has the right frequency 10mhz, but MOSI is wrong.

Hardware: ST MCU STM32L496AGI6P, OLED with SPI interface
Zephyr Ver: Zephyr OS 2.7.0-rc2 .
OS: Linux Ubuntu

Analysis:
Attached SPI_CLK_5mhz.jpg is the 5mhz SPI clock when I try to write 0x55 0xaa. The OLED uses SPI clock rising edge to latch MOSI data.(CH1:SPI clock, CH2:SPI MOSI)
Attached SPI_CLK_10mhz_0x55.jpg is the 10mhz SPI clock when I try to write 0x55.
Attached SPI_CLK_10mhz_0xAA.jpg is the10mhz SPI clock when I try to write 0xAA.

When I build the firmware without Zephyr OS, using the same hardware as mentioned above , the MOSI is correct when SPI clock is configured at 20mhz. So the hardware should be no problem.

Below is how SPI and clock system get configured in DTS.

&clk_hsi {
status = "okay";
};

&pll {
div-m = <1>;
mul-n = <20>;
div-p = <7>;
div-q = <2>;
div-r = <4>;
clocks = <&clk_hsi>;
status = "okay";
};

&rcc {
clocks = <&pll>;
clock-frequency = <DT_FREQ_M(80)>;
ahb-prescaler = <1>;
apb1-prescaler = <1>;
apb2-prescaler = <1>;
};

&spi1 {
pinctrl-0 = <&spi1_sck_pa5 &spi1_miso_pb4 &spi1_mosi_pb5>;
status = "okay";
};

Please advise me how to fix this problem. Thank You!

[erwango]

@glin00 can you try to change pin speed, adding the following to board.dts file

&spi1_mosi_pb5{
slew-rate = "very-high-speed";
};

[glin00]

@erwango with your advise, the MOSI is correct. Thanks.