failing to generate a random number using stm32f4xx_rng

[raiyans]

Posted on November 10, 2016 at 17:34

Hi all,

I am using an stm32f4 micro to generate a random number. I am using the RNG Driver from the stm32cubef4 library. I followed the examples but the micro is generating the same number over and over again. here is a code snippet.

int
main(
void
)

{

HAL_Init();

system_init();

if
(HAL_RNG_Init(&hRNG1) != HAL_OK)

{

DEBUG_PRINT(
''Random Number generation failed\r''
);

}

if
(HAL_RNG_GenerateRandomNumber(&hRNG1,code_)==HAL_OK)

{

DEBUG_PRINT(
''RNG initiated\r''
);

}

else

{

DEBUG_PRINT(
''RNG failed\r''
);

}

DEBUG_PRINT(
''%''
PRIu32 
''\r''
,code_[0]);

}

Does anybody have a clue on what am missing. I am using the DEBUG_PRINT function to get the random value through the serial port. Best Regards Raiyan #no-hablo-hal #stm32f407-random-number-generate

[Tesla DeLorean]

Posted on November 10, 2016 at 20:18

What does it actually output?

The RNG must have its AHB clock enabled, and the PLL Q must be clocking and outputting 48MHz. Things won't work if the PLL isn't running.Review the Reference Manual, examine the registers and settings directly.

[Tesla DeLorean]

Posted on November 10, 2016 at 20:21

Don't exit main()

Provide output from

while(1)
{
 DEBUG_PRINT(''%'' PRIu32 ''
'',code_[0]);
 HAL_RNG_GenerateRandomNumber(&hRNG1,code_);



}

[raiyans]

Posted on November 11, 2016 at 10:56

There you go 😉 I have initiated the rng clock as suggested in the documentations.

[Tesla DeLorean]

Posted on November 11, 2016 at 17:20

Does this work?

code_[0] = 12345;
DEBUG_PRINT(''%'' PRIu32 ''
'',code_[0]);

I might examine the RNG hardware on the F4 under the SPL if I get time. You should review the Reference Manual, and output/advance the registers manually.

[Tesla DeLorean]

Posted on November 11, 2016 at 21:07

Interestingly the STM32F446ZE doesn't have an RNG

On the STM32F429ZI I had more joy

void RNG_Configuration(void)
{
/* Enable RNG clock source */
RCC_AHB2PeriphClockCmd(RCC_AHB2Periph_RNG, ENABLE);
/* RNG Peripheral enable */
RNG_Cmd(ENABLE);
}
...
RNG_Configuration();
printf(''%10lu
'', RNG_GetRandomNumber());
printf(''%10lu
'', RNG_GetRandomNumber());
printf(''%10lu
'', RNG_GetRandomNumber());
printf(''%10lu
'', RNG_GetRandomNumber());
...
1820376166
544183808
417758785
2790747703

[raiyans · Accepted solution]

Posted on November 14, 2016 at 12:01

Hi clive1,

I finally managed to solve the issue. What I was missing from the code is the instance initiation and a correct PLL clock initiation

RNG_HandleTypeDef hRNG1;
int
main()
{
hRNG1.Instance = RNG;
}
and also I might have not configured my PLL correctly. Now I configured it as follow
/*Enable HSE Oscillator and activate PLL with HSE as source*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 25;
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2
clocks dividers*/
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);

Thanks a lot for your help Regards from Austria,