Can the Leonardo Arduino be used as a USB HOST for CDC Com devices?

Question

I am trying to connect a CDC communication device to the Leonardo USB port and have communication with it via the TTL com port. Basically I want to echo to the TTL port whatever is transmitted over USB and vice-versa.

ASCII data is transmitted out the USB from the CDC device into the USB port of the Leonardo Aurduino. The Arduino needs to xtransfer this info over to the UART pins D0 (RX) and D1 (TX) that are connected to the UART of another micro-controller. I should be able to test it by connecting an FTDI TTL-RS232 cable and see results and have comms in my terminal program.

I came across this sketch that appears to be basically what I want, but I think the "hosting" portion is not being set up:

void setup() {
 Serial.begin(9600); // rx/tx pins
 Serial1.begin(9600); // USB port
 Serial1.write("2nd Version");
} 
void loop() {
 // copy from virtual serial line to UART and vice-versa
 if (Serial.available()) {
 char c = (char)Serial.read();
 Serial1.write(c);
 }
 if (Serial1.available()) {
 char c = (char)Serial1.read();
 Serial.write(c);
 } 
}

What am I missing? Note I am NOT trying to do HID but CDC. Basically I want to eliminate using a PC as a Host device and use the "bridge" between my CDC device and another micro-controller.

• user31481: Interesting. I do know nothing about CDC. Can you show us a schematic showing the connectiions?
• AA9GG: Nothing to it really....ASCII data is transmitted out the USB from CDC device into USB Port of the Leonardo Aurduino. The Aurduino needs to xtransfer this info over to the UART pins D0(RX) and D1(TX) that is connected to the UART of another microcontroller. I should be able to test it by connecting an FTDI ttl-RS232 cable and see results and have comms in my terminal program

Answer 1

No, the Leonardo cannot be a USB Host. You may be able to use a USB Host Shield in conjunction with the Leonardo, though I have never tried it and cannot vouch for compatibility with the Leonardo.

USB is a host->device protocol, not a peer-to-peer protocol. You cannot just connect two devices together. Only a USB Host can communicate with a USB device.

• user31481: Not even with an OTG cable?
• Majenko: No. The Leonardo cannot be a USB Host.