CMSIS Driver UART Revision: V1.02
file C:\Keil\ARM\Pack\Keil\STM32F4xx_DFP\1.0.8\RTE_Driver\UART_STM32F4xx
function UART_ReadData
static int32_t UART_ReadData (uint8_t *data, uint32_t size, UART_RESOURCES *ptr_uart) { volatile uint32_t val; osMutexWait(ptr_uart->info->mutex_read, osWaitForever); if ((size == 0) || (ptr_uart->info->rx.empty == true)) { osMutexRelease(ptr_uart->info->mutex_read); return 0; } val = (ptr_uart->info->rx.idx_in - ptr_uart->info->rx.idx_out) & (ptr_uart->rx_buffer_size - 1); if (val == 0) val = ptr_uart->rx_buffer_size; if (size > val) size = val; if ((ptr_uart->hw_flow == true) && (ptr_uart->manual_rts_cts == false)) { if (ptr_uart->flow_ctrl_threshold < val) GPIO_PinWrite(ptr_uart->pin_rts.port, ptr_uart->pin_rts.num, 0); } if (size > (ptr_uart->rx_buffer_size - ptr_uart->info->rx.idx_out)) { memcpy(data, ptr_uart->rx_buffer + ptr_uart->info->rx.idx_out, val); memcpy(data + val, ptr_uart->rx_buffer, size - val); if (ptr_uart->info->rx.idx_in == (size - val)) ptr_uart->info->rx.empty = true; ptr_uart->info->rx.idx_out = size - val; } else { memcpy(data, ptr_uart->rx_buffer + ptr_uart->info->rx.idx_out, size); val = (ptr_uart->info->rx.idx_out + size) & (ptr_uart->rx_buffer_size - 1); if (ptr_uart->info->rx.idx_in == val) ptr_uart->info->rx.empty = true; ptr_uart->info->rx.idx_out = val; }
Guess what will be if variable size is less than val?
The first memcpy is not correct also, because it over reads the input buffer. So first I've added the following line before the first memcpy:
//number of characters before the end of the input buffer val=ptr_uart->rx_buffer_size-ptr_uart->info->rx.idx_out;
After I've added this line, then I checked the following logic, and everything seems to be correct. So finally the code, which is works fine for me:
if (size > (ptr_uart->rx_buffer_size - ptr_uart->info->rx.idx_out)) { val=ptr_uart->rx_buffer_size-ptr_uart->info->rx.idx_out; memcpy(data, ptr_uart->rx_buffer + ptr_uart->info->rx.idx_out, val); memcpy(data + val, ptr_uart->rx_buffer, size - val); if (ptr_uart->info->rx.idx_in == (size - val)){ ptr_uart->info->rx.empty = true; } ptr_uart->info->rx.idx_out = size - val; }
When I tested the original version, that causes hard fault. The same test works fine with this modified version. There is no hard fault, nor data losses.
I hope, that I didn't make another bug, which is not discovered yet, but if yes, please post a comment.
Attila Zombori
For the special case where the processor has 2^n wide registers with "traditional" overflow of unsigned integers and where the ring buffer has 2^n elements, it would have been way better if you had completely rewritten the code into a more classical ring-buffer solution. This CMSIS implementation is just poor code from the start.
right,it is good,also bug in other dirvers for ST like STM32F10X,STM32F20X,STM32F30X