Arduino and USB Serial UART

Hello forum,

I have my Arduino UNO pumping out serial messages. I have a USB Serial UART connect on another port. I have connected the TX of the Arduino to RX of the USB Serial UART and the RX of the Arduino to the TX of the Serial UART. I have also joint the grounds of both devices. I have a serial monitor open on both port. However, I can only see the Arduino sending message through it's in build UART, nothing from the USB Serial UART.

Sound I be able to see the output of the Arduino through the Serial UART?

Kind Regards, Harold Clements

PS, I am just trying to test the USB Serial UART.

Check the tx line of your USB-TTL adapter with a multimeter; it should be 3.3 or 5v (idle state voltage). https://www.sparkfun.com/tutorials/215

Your adapter likely has LEDs for tx and rx activity. If you short the rx line to ground, the rx LED should come on.

haroldjclements: Hello forum,

I have my Arduino UNO pumping out serial messages. I have a USB Serial UART connect on another port. I have connected the TX of the Arduino to RX of the USB Serial UART and the RX of the Arduino to the TX of the Serial UART. I have also joint the grounds of both devices. I have a serial monitor open on both port. However, I can only see the Arduino sending message through it's in build UART, nothing from the USB Serial UART.

Sound I be able to see the output of the Arduino through the Serial UART?

Kind Regards, Harold Clements

PS, I am just trying to test the USB Serial UART.

You didn't say, so I ask ... Same Baud Rate? Same # Data Bits? Same # Stop Bits? Same Parity Bits?

Does the USB UART need DSR, CTS or DCD pins set to enable communications?

Thank you very much for your replies...

I have managed to get the USB-UART device talking as a loop back, but cannot get any other communication. I will answer the questions asked one by one.

Check the tx line of your USB-TTL adapter with a multimeter; it should be 3.3 or 5v (idle state voltage). Yes, I get 3.3V.

Your adapter likely has LEDs for tx and rx activity. Yes, but I only have the one LED (DATA).

If you short the rx line to ground, the rx LED should come on. As I only have a DATA LED, I am not too sure it makes a difference to the question now, but; NO shorting of RX to ground does NOT turn the DATA LED on.

You didn't say, so I ask ... CP210x USB to UART Bridge (COM4) Baud Rate: 9600 Data Bits: 8 Stop Bits: 1 Parity Bits: None Flow Control: None

I am not too sure how to check on the Arduino; Device Manager say's the following, but I am not sure if that relates to the PC -> Ardunio comms rather then Adrunio -> USB UART.

Arduino Uno (COM3) QBaud Rate: 9600 Data Bits: 8 Stop Bits: 1 Parity Bits: None Flow Control: None

Does the USB UART need DSR, CTS or DCD pins set to enable communications? This USB device only has GND, RX, TX, 5V, RST, 3.3V pins showing, I do not know how you would set DSR, CTS or DCD pins.

Do do appreciate your time and effort in helping me with this issue...

Kind Regards, Harold Clements

Hello guys... I don't know how... but I appear to have solved the problem....

The only thing I can think of (as I did not change any settings) is that I wired it up wrong (despite checking 1000 times) before posting.

Anyhow, thanks very much for your time. Harold Clements