Wio Terminal RTL8720D UART Transport Passthrough

erpc_debug_passthrough.ino

#include <wiring_private.h>

#define PIN_BLE_SERIAL_X_RX (84ul)
#define PIN_BLE_SERIAL_X_TX (85ul)
#define PAD_BLE_SERIAL_X_RX (SERCOM_RX_PAD_2)
#define PAD_BLE_SERIAL_X_TX (UART_TX_PAD_0)
#define SERCOM_BLE_SERIAL_X sercom0

static Uart rtl_uart(&SERCOM_BLE_SERIAL_X, PIN_BLE_SERIAL_X_RX, PIN_BLE_SERIAL_X_TX, PAD_BLE_SERIAL_X_RX, PAD_BLE_SERIAL_X_TX);

extern "C" {
    void SERCOM0_0_Handler()
    {
      rtl_uart.IrqHandler();
    }
    void SERCOM0_1_Handler()
    {
        rtl_uart.IrqHandler();
    }
    void SERCOM0_2_Handler()
    {
        rtl_uart.IrqHandler();
    }
    void SERCOM0_3_Handler()
    {
        rtl_uart.IrqHandler();
    }
}

void setup()
{
    Serial.begin(115200);
    while(!Serial);
    rtl_uart.begin(1843200);
    //rtl_uart.begin(115200);
    rtl_uart.setTimeout(10 * 1000);

    pinMode(RTL8720D_CHIP_PU, OUTPUT);
    digitalWrite(RTL8720D_CHIP_PU, LOW);
    delay(100);
    digitalWrite(RTL8720D_CHIP_PU, HIGH);
    delay(100);

    
    digitalWrite(RTL8720D_CHIP_PU, LOW);
    delay(100);
    digitalWrite(RTL8720D_CHIP_PU, HIGH);
    delay(100);
}

char buf4[4];
char buf[0x0400];
int idx;

void loop()
{
    if (Serial.available() > 0)
    {
        char c = Serial.read();
        rtl_uart.write(c);
    }

    if (idx == 0) {
        if (rtl_uart.available() > 0)
        {
            rtl_uart.readBytes(buf4, 4);
            idx = buf4[0] + (buf4[1]<<8);
            for (int i = 0; i < 4; i++) {
                Serial.write(buf4[i]);
            }
        }
    } else {
        if (rtl_uart.available() > 0) {
            rtl_uart.readBytes(buf, idx);
            for (int i = 0; i < idx; i++) {
                Serial.write(buf[i]);
            }
            idx = 0;
        }
    }
}

以下をベースに作成。
元コードだと、 read の速度が足りてないのか欠落してしまっている感じ。
https://gist.github.com/ciniml/5521e556cc1740b973858a5249a88da7