I have a 2-board communication project set up with 2 NUCLEO-H753ZI boards, where they communicate over UART. The sender side sends a 22-byte stream of data that is received by the receiver side and gets parsed into data. This data can then be streamed to a PC over Ethernet.
Inside of the UART_RxCpltCallback, I toggle the Red on-board LED, which gives me the rate at which packets are coming in. Inside the UART_TxCpltCallback I am calling a function that takes the data from the UART buffer, and moves it into a member variable of an object. All this should happen at 2KHz, but for some reason the data is only updating every few seconds, and it is not a specific rate at which it updates, it seems random. The graph might better illustrate what I am talking about. The graph *should* look like a sawtooth waveform.
The confusing part is that the LEDs work as expected, i.e. those blocks of code that are responsible for getting the data where it needs to be are surely executing, they just don't seem to do the thing I think they are doing.
AFAIK the receive buffer being used is in a non-cacheable region, so the issue should not be MPU or cache related.
void MPU_Config(void)
{
MPU_Region_InitTypeDef MPU_InitStruct = {0};
/* Disables the MPU */
HAL_MPU_Disable();
/** Initializes and configures the Region and the memory to be protected
*/
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.Number = MPU_REGION_NUMBER0;
MPU_InitStruct.BaseAddress = 0x0;
MPU_InitStruct.Size = MPU_REGION_SIZE_4GB;
MPU_InitStruct.SubRegionDisable = 0x87;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
MPU_InitStruct.AccessPermission = MPU_REGION_NO_ACCESS;
MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);
/** Initializes and configures the Region and the memory to be protected
*/
MPU_InitStruct.Number = MPU_REGION_NUMBER1;
MPU_InitStruct.BaseAddress = 0x30010000;
MPU_InitStruct.Size = MPU_REGION_SIZE_64KB;
MPU_InitStruct.SubRegionDisable = 0x0;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL1;
MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);
/** Initializes and configures the Region and the memory to be protected
*/
MPU_InitStruct.Number = MPU_REGION_NUMBER2;
MPU_InitStruct.BaseAddress = 0x30020000;
MPU_InitStruct.Size = MPU_REGION_SIZE_128KB;
HAL_MPU_ConfigRegion(&MPU_InitStruct);
/** Initializes and configures the Region and the memory to be protected
*/
MPU_InitStruct.Number = MPU_REGION_NUMBER3;
MPU_InitStruct.BaseAddress = 0x30040000;
MPU_InitStruct.Size = MPU_REGION_SIZE_512B;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);
/* Enables the MPU */
HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);
}
Linked script snippet:
{
. = ALIGN(8);
. = ABSOLUTE(0x30000000);
*(.RxUsartBuffer)
. = ALIGN(8);
. = ABSOLUTE(0x30008000);
*(.TxBuffer)
. = ALIGN(8);
. = ABSOLUTE(0x30010000);
*(.Adc1Buffer)
. = ALIGN(8);
. = ABSOLUTE(0x30014000);
*(.Adc2Buffer)
. = ALIGN(8);
. = ABSOLUTE(0x30018000);
*(.Adc3Buffer)
. = ALIGN(8);
. = ABSOLUTE(0x30040000);
*(.RxDecripSection)
. = ALIGN(8);
. = ABSOLUTE(0x30040100);
*(.TxDecripSection)
. = ALIGN(8);
. = ABSOLUTE(0x30040200);
*(.Rx_PoolSection)
. = ALIGN(8);
} >RAM_D2and the buffer
std::array<uint8_t, SerialRxBuffer::kSize> SerialCommunication::rx_buffer_
__attribute__((section(".RxUsartBuffer")));
