PIC18F4550 USB Serial
For more C sample code, see www.MicrochipC.com.
USB example for Microchip PIC18F4550.
Connect a USB cable directly to the pins of a pre-programmed PIC18F4550, add capacitor and crystal, and you have a virtual COMx serial port.
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Plug your PIC18F4550 into your PC using a USB cable. A virtual RS232 COM port is created, allowing your application to print RS232 messages into HyperTerminal. Allows porting of legacy code that used RS232 comms.
Note: ensure that you read "readme (including install notes).txt" after download.
Schematic and PCB
This code runs on the PICDEM-FS board from Microchip.
This board is no longer available, but its easy to make your own circuit:
- Place a preprogrammed PIC18F4550 on a breadboard.
- Ensure that you are using a 20Mhz crystal.
- Place a 470nF capacitor on port Vusb.
- Hook the USB wires directly to the chip.
- It should start to work straight away. Download the PICDEM-FS datasheet for the exact schematic to use with this code.
- Start up any program which can monitor a standard serial port, such as HyperTerminal or putty.
- Find the new COMx port that has been enumerated.
- Set it to 115200,N,8,1.
- The actual COM port speed doesn't matter, as its a virtual comm port.
- You will see "[alive]" being continuously generated on virtual com port X over USB.
- You can find the exact number of the virtual COM port by going into "Control Panel", then "System", then selecting the "Hardware" then "Device Manager", there will be a new COM port under "Ports (COM & LPT). You can change the number of the virtual comm port by going into properties, and selecting the new COM port.
11th Nov 2007 Tried it on Hi-Tech C v9.62, it worked. Had reports that it does not work on Hi-Tech C v9.51.
2nd Feb 2009 Customer got it working with Hi-Tech C v9.51, it worked after some tweaks. Added instructions to v1.10 of the download.
More C Sample Code
For more sample code, see www.MicrochipC.com.
Do you have any enhancements to share with the community? We honour 98% of pull requests within a few days!