ESP32 TF卡读写性能优化

1 将SPI时钟速度调到16M

 if (!SD.begin(SS, SPI, 16000000))
    {
        Serial.println("Card Mount Failed");
        return;
    }

DSTATUS ff_sd_initialize(uint8_t pdrv)
{
    char token;
    unsigned int resp;
    unsigned int start;
    ardu_sdcard_t * card = s_cards[pdrv];

    if (!(card->status & STA_NOINIT)) {
        return card->status;
    }

    AcquireSPI card_locked(card, 16000000);
    ....

1. 每次读写的字节数
2. 调整读写异常时的延时函数

char sdCommand(uint8_t pdrv, char cmd, unsigned int arg, unsigned int* resp)
{
    ...
        // Serial.printf("%s.%d : %u. token = %d
","sd_diskio",__LINE__,millis(),token);
        if (token == 0xFF) {
            log_w("no token received");
            sdDeselectCard(pdrv);
            sdDeselectCard(pdrv);// 变更此处的延时处理
            // delay(1);
            sdSelectCard(pdrv);
            sdSelectCard(pdrv);
            continue;
        } else if (token & 0x08) {
            log_w("crc error");
            sdDeselectCard(pdrv);
            sdDeselectCard(pdrv);// 变更此处的延时处理
            // delay(1);
            sdSelectCard(pdrv);
            sdSelectCard(pdrv);
            continue;
        } else if (token > 1) {
            log_w("token error [%u] 0x%x", cmd, token);
            break;
        }
...
}