环境：
CubeMX（5.2.1）
HAL库（1.15.0）
STM32F765IIK（主频180MHz，关闭Cache）
SDMMC2+DMA
FATFS（R0.12c）
测试程序：
void sdcard_test_task(void *p) {
static FATFS fs;
FIL fil;
uint32_t bw;
const char *w = "1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n"
"1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234_1234\r\n";
if (f_mount(&fs, "0:", 1)) {
__nop();
return;
}
while (1) {
if (f_open(&fil, "ggg.txt", FA_OPEN_ALWAYS | FA_WRITE) == FR_OK) {
f_lseek(&fil, f_size(&fil));
f_write(&fil, w, strlen(w), &bw);
f_close(&fil);
} else {
__nop();
}
HAL_Delay(100);
}
}
问题：
程序运行一段时间后f_open一直返回FR_LOCKED错误
解决：
重新打开CubeMX，把FATFS的这栏选成Enable即可
其他：
这个版本的CubeMX和HAL库使用SD卡必须打开DMA产生TXUNDERR错误：
解决办法是打开I，DCache
别忘了栈可能要调大我在STM32F429I-DISCOVERY这个板子上也试过用CubeMX（5.4.0）生成的代码（HAL库V1.24.1）调试SD卡，也遇到了类似的问题。具体是SD卡可以写但不能读，读出错的原因是SDIO_FLAG_RXOVERR，解决办法是把HAL_SD_ConfigWideBusOperation(&hsd, SDIO_BUS_WIDE_4B)中的SDIO_BUS_WIDE_4B改成SDIO_BUS_WIDE_1B
