USART1 and hard fault

[Diego Colombo]

Posted on January 05, 2018 at 10:59

Hi and happy new year

I need help,to avoid an hard fault after un unpredictable time(2 ...120 sec) when i use the USART1 Tx

MCU is STM32F410RBT,mounted on a custom board

Configuration done with CubeMx,IDE is STM32 Workbench

I have to acquire 12 analog channels at 1KHz,then i have to send the data to a PC using USART1 at 460800 bps

I trigger the ADC with TIM1,then the ADC transfers in DMA the 12 x 12 bit samples to a 16 bit buffer

unsigned short ADC1ConvertedValues[ADC_BUFFER_SIZE];

I associated some interrupt to the timer event ,to the end of 12 channels conversions and to the end of ADC DMA transfer,

in these interrupt routines i move somo pin so that i can't verify on the scope the activities.

Channel1-yellow and channel 2-blue goes high when the TIM event happens

Channel 1 goes low ath the end of ADC conversions,Channel 2 goes low at the end of ADC DMA transfer

A 3rd scope -green channel is connected to the UART Tx pin

First thing i notice is that the ADC DMA transfer pulse is prior than the ADC EoC,maybe because of the highest priority of the DMA transfer interrupt?

Anyway everything looks okay until here.

In the DMA interrupt routine i call HAL_UART_Transmit_DMA(&huart1, (uint8_t *)buff_char_prova, 20);

or i simply turn on a flag that calls the same function in the main loop.

After some seconds i have hard fault ,the same happens if i call 

HAL_UART_Transmit_IT(&huart1, (uint8_t *)buff_char_prova, 20);

 

or the blocking function 

HAL_UART_Transmit(&huart1, (uint8_t *)buff_char_prova, 20);//(in main loop)

Saving the content of registers and program counter PC during hard fault shows every time a different  PC value.

May i have some help,please ?

Attached is the whole project,including CubeMx file.

Many thanks for your time.

Diego,

Milan ,Italy

[Bogdan Golab]

Posted on January 05, 2018 at 11:46

I use the KEIL IDE and during the debugging and hard fault I can see what kind of hard fault occured (hard fault type):

http://www.keil.com/appnotes/files/apnt209.pdf

 

Since you get different PC value each time it means that the code that crashed is NOT deterministic (not the same code) because the data from the ADC is random and influence the code (location for example), or more likely the stack (changing the return addresses of called functions).

Check the stack size defined, especially if the buffer for adc data is allocated inside a function (main() is also a function) because the array is allocated on the stack.

Instead you can simply allocate the array as global variable (outside main() or any other function) to see if it helps.

It's a guess only.

[Bogdan Golab]

Posted on January 05, 2018 at 11:53

Moving the array outside any function cause array to be allocated outside the stack and heap (assumed that the array size is known to the compiler, not dynamic array)

[Tesla DeLorean]

Posted on January 05, 2018 at 18:31

Double check FLASH Wait States, classic cause of random Hard Faults.

Check voltage on VCAP pins.

[Diego Colombo]

Posted on January 06, 2018 at 16:21

Thanks Bogdan , Doug and Clive

SOLVED.It depended by hardware:

As you can see it is not exactly professional:

anyway

1)I put some capacitor closer to VDD pins

2)I added 3 'wired vias' across the 2 ground planes

3)last but probably more important,i have soldered better the 0402 sized VCAP pin capacitor, it was probably disconnected

In over 20 hours i never had hard fault,despite i doubled the core speed at 96MHz.

The misleading things were:

1)Previous lucky experiences with similar mounting and only few caps

2)The fact that the hard fault never happened with this code,unless activating USART1

Thanks again for help

[Tesla DeLorean]

Posted on January 06, 2018 at 18:42

I seem to recall ST using 0603 caps for VCAP. For the single cap implementation 4.7uF with ESR less than 1Ohm. This is the bulk capacitance for the internal 1.25V regulator the core is running from.