Redirecting RS232 data using HW and SW USART on PIC18F4220

jpage · Joined: 23 Jun 2004 Posts: 24

I am interfacing with a device connected to a PIC18F4220 and want to communicate with the device by using RS232 from a Host computer.

The device is connected the PIC18F4220 using pins B2 and B1.

B1 is reading data transmitted from device and B2 is sending data to device.

I am using the onboard USART to communicate with the Host computer via RS232 on pin C6 and C7.

I want to take the data on pins B2 or B1 and redirect the data to or from the USART.

I would appreciate any feedback on any methods to accomplish this. Thanks.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Guest · Posted: Wed Jun 23, 2004 2:45 pm

Communications for the device on pins B1 and B2 is RS232.

And yes it does transfer data in 8 bit Bytes.

I have had the device connected directly to my computer serial (COM1) and am able to transfer data with no problem.

Only this time, I will need to go through the PIC's USART and redirect to the data through pins B1 and B2. This is where I need some ideas in how to accomplish this.

dyeatman · Joined: 06 Sep 2003 Posts: 1933 Location: Norman, OK

What you want to do can't be done to my knowledge. What I have done in the past is use an RS232 multiplexer chip to switch B6/B7 between multiple RS232 sources. I did this to service 5 different LCD displays and it worked fine. The only limitations are that you cant have the different channels transmitting/receiving at the same time and they must all be the same bits/stop bits. You have to service them sequentially to use the mux..

Your only other option is to use a chip with two hardware USARTS.