/* This low-level send bytes function is NON-BLOCKING; blocking behavior, with
* a timeout, is implemented in usercode (or in the Wirish C++ high level
* implementation).
*
* This function will quickly copy up to 64 bytes of data (out of an
* arbitrarily large buffer) into the USB peripheral TX buffer and return the
* number placed in that buffer. It is up to usercode to divide larger packets
* into 64-byte chunks to guarantee delivery. Use usbGetCountTx() to determine
* whether the bytes were ACTUALLY recieved by the host or just transfered to
* the buffer.
*
* The function will return -1 if it doesn't think that the USB host is
* "connected", but it can't detect this state robustly. "Connected" in this
* context means that an actual program on the Host operating system is
* connected to the virtual COM/ttyACM device and is recieving the bytes; the
* Host operating system is almost always configured and keeping this endpoint
* alive, but the bytes never get read out of the endpoint buffer.
*
* The behavior of this function is subtle and frustrating; it has gone through
* many simpler and cleaner implementation that frustratingly don't work cross
* platform.
*
* */
uint16 usbSendBytes(uint8* sendBuf, uint16 len) {
uint16 loaded = 0;
if (bDeviceState != CONFIGURED || (!usbGetDTR() && !usbGetRTS())) {
// Indicates to caller to stop trying, were not configured/connected
// The DTR and RTS lines are handled differently on major platforms, so
// the above logic is unreliable
return 0;
}
// Due to a variety of shit this is how we roll; all buffering etc is pushed
// upstream
if (countTx) {
return 0;
}
// We can only put VCOM_TX_EPSIZE bytes in the buffer
if(len > VCOM_TX_EPSIZE) {
loaded = VCOM_TX_EPSIZE;
} else {
loaded = len;
}
// Try to load some bytes if we can
if (loaded) {
UserToPMABufferCopy(sendBuf,VCOM_TX_ADDR + countTx, loaded);
_SetEPTxCount(VCOM_TX_ENDP, countTx+loaded);
_SetEPTxValid(VCOM_TX_ENDP);
countTx += loaded;
}
return loaded;
}
void loop() {
toggle ^= 1;
digitalWrite(LED_PIN, toggle);
delay(100);
Serial2.print("DTR: ");
Serial2.print(usbGetDTR(), DEC);
Serial2.print("\tRTS: ");
Serial2.println(usbGetRTS(), DEC);
}
uint8 USBSerial::getRTS(void) {
return usbGetRTS();
}
