Debby Polykarpou

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11 years, 10 months ago.

USB signal to Serial signal

Hello,

I have my Mbed connected to PC, through USB pins (D+, D-) (I used USBserial library to do that). and I want to send the received signals from PC (and therefore from USB) to another device, using a UART port from Mbed. How can I send the signals received from my PC to the other device using UART port? Do I have to convert the USB signals to Serial signals and then use the UART port??

Thank you in advance for any help

3 Answers

X M
11 years, 10 months ago.

If you use a real ( not virtual , through USB ) serial port (real RS232 , + - 12 volt levels ), you have to use a level shifter, such as MAX3232 ( 3V to RS232 levels ) Have a look at Keil MCB1700 schematic , at IC6 http://www.keil.com/mcb1700/

If you connect at microcontroller level ( between 2 same voltage microcontroller serial ports ) and the distance is short and you have no noise , then you can ommit the buffers ( max3232 ) from both sides .

Do not confuse max3232 with ft232RL etc ! ( buffer ,receiver vs serial to USB )

Regards, Christos

Accepted Answer
avnish aggarwal
11 years, 10 months ago.

You will send/receive ASCII characters from the PC over the serial USB interface.

Open another serial "port" to the device you want to connect to - and act as a passthrough between that device and the USB device. Should be about less than 10 lines of code.

Debby Polykarpou
poster
11 years, 10 months ago.

Thank you for your reply. Just to make sure, there is no need to use a USB to serial converter (FT232BM) before passing the data to the other device, through serial port?