Trouble using LPUART eDMA on Coral Micro board

[andreas90]

Hi,

I'm trying to use a Coral Micro Dev board, which features an RT1176 MCU, to facilitate UART communication via UART2 to a custom board. Basically, I want to send a single byte via UART to the board, receive a large chunk of data (about 64K) in return, process that, repeat. This works (in principle), if I use the LPUART_WriteBlocking and LPUART_ReadBlocking functions from the LPUART driver (fsl_lpuart.c). However, probably due to the very high datarate, I occasionally received RxHardwareOverrun error, so I tried implementing the same functionality using the EDMA unit instead.

Unfortunately, this didn't work at all. While I can send data via UART2 using LPUART_SendEDMA, the board subsequently resets itself, presumably when trying to call the corresponding ISR upon TxIdle. With a JTAG debugger connected, the board does not reboot, but the PC ends up stuck at address 0x00223104.

Here's a short example of my code:

#include <cstdio>
#include <inttypes.h>
#include <FreeRTOS.h>
#include <task.h>
#include "fsl_lpuart.h"
#include "fsl_lpuart_edma.h"
#include "fsl_dmamux.h"
#include "libs/base/led.h"
#include "MIMXRT1176_cm7.h"

void LPUART_UserCallback(LPUART_Type *base, lpuart_edma_handle_t *handle, status_t status, void *userData);

edma_handle_t tx_edma_handle;
edma_handle_t rx_edma_handle;
lpuart_edma_handle_t lpuart_edma_handle;
lpuart_transfer_t sendXfer;

AT_NONCACHEABLE_SECTION(uint8_t rx_edma_buffer[8192]);
AT_NONCACHEABLE_SECTION(uint8_t tx_edma_buffer[8]);

void LPUART_UserCallback(LPUART_Type *base, lpuart_edma_handle_t *handle, status_t status, void *userData) {
    // nothing yet
}

extern "C" [[noreturn]] void app_main(void *param) {
    (void)param;

    vTaskDelay(pdMS_TO_TICKS(5000));

    clock_root_config_t root_cfg = {0};
    lpuart_config_t lpuart_config;
    edma_config_t edma_config;

    root_cfg.mux = kCLOCK_LPUART2_ClockRoot_MuxOscRc400M;
    root_cfg.div = 5;
    CLOCK_SetRootClock(kCLOCK_Root_Lpuart2, &root_cfg);
    
    LPUART_GetDefaultConfig(&lpuart_config);
    lpuart_config.baudRate_Bps  = 6000000;
    lpuart_config.enableTx      = true;
    lpuart_config.enableRx      = true;
    lpuart_config.parityMode    = kLPUART_ParityDisabled;
    lpuart_config.stopBitCount  = kLPUART_OneStopBit;
    lpuart_config.dataBitsCount = kLPUART_EightDataBits;
    LPUART_Init(LPUART2, &lpuart_config, CLOCK_GetRootClockFreq(kCLOCK_Root_Lpuart2));

    DMAMUX_Init(DMAMUX0);
    DMAMUX_SetSource(DMAMUX0, 0U, kDmaRequestMuxLPUART2Tx);
    DMAMUX_SetSource(DMAMUX0, 1U, kDmaRequestMuxLPUART2Rx);
    DMAMUX_EnableChannel(DMAMUX0, 0U);
    DMAMUX_EnableChannel(DMAMUX0, 1U);

    EDMA_GetDefaultConfig(&edma_config);
    EDMA_Init(DMA0, &edma_config);
    EDMA_CreateHandle(&tx_edma_handle, DMA0, 0U);
    EDMA_CreateHandle(&rx_edma_handle, DMA0, 1U);
    LPUART_TransferCreateHandleEDMA(LPUART2, &lpuart_edma_handle, LPUART_UserCallback, NULL, &tx_edma_handle, &rx_edma_handle);
   
    sendXfer.data = &tx_edma_buffer[0];
    sendXfer.dataSize = 1;
    LPUART_SendEDMA(LPUART2, &lpuart_edma_handle, &sendXfer);

    while (true);
}

And here's the CMakeLists.txt I'm using to build my project:

cmake_minimum_required(VERSION 3.13)

# Toolchain must be set before project() call.
if (NOT DEFINED CMAKE_TOOLCHAIN_FILE)
    set(CMAKE_TOOLCHAIN_FILE ${CMAKE_CURRENT_LIST_DIR}/coralmicro/cmake/toolchain-arm-none-eabi-gcc.cmake)
endif()

project(coralmicro-app CXX C ASM)

set(CMAKE_BUILD_TYPE Release)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)

include_directories(coralmicro)
add_subdirectory(coralmicro)

add_executable_m7(coralmicro-app
    main_cm7.cc
    ${CMAKE_CURRENT_SOURCE_DIR}/coralmicro/third_party/nxp/rt1176-sdk/devices/MIMXRT1176/drivers/fsl_lpuart_edma.c
)

target_include_directories(coralmicro-app PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}
    ${CMAKE_CURRENT_SOURCE_DIR}/coralmicro
    ${CMAKE_CURRENT_SOURCE_DIR}/coralmicro/third_party/CMSIS/CMSIS/Core/Include
    ${CMAKE_CURRENT_SOURCE_DIR}/coralmicro/third_party/nxp/rt1176-sdk/devices/MIMXRT1176/drivers
)

target_link_libraries(coralmicro-app PRIVATE -Wl,--start-group)
target_link_libraries(coralmicro-app PRIVATE libs_base-m7_freertos)
target_link_libraries(coralmicro-app PRIVATE libs_nxp_rt1176-sdk_freertos)
target_link_libraries(coralmicro-app PRIVATE m)
target_link_libraries(coralmicro-app PRIVATE c)
target_link_libraries(coralmicro-app PRIVATE gcc)
target_link_libraries(coralmicro-app PRIVATE nosys)
target_link_libraries(coralmicro-app PRIVATE -Wl,--end-group)

What am I missing here? Is there some additional configuration to be done to make this work?

Any help is greatly appreciated...

Thanks!

[Omar_Anguiano · Accepted solution]

Once sent the date you can add the function LPUART_ReceiveEDMA() to start receiving.
Make sure that DMA channels and interruption are enabled. 

Best regards,
Omar