Hi All,

I'm relatively new to the world of microcontrollers, and I'm currently working on a project with a AT89C2051 chip as the main chip.

The project is to make a simple calculator but with intentions to turn it into a serial I/O device for integration into later projects. I'm currently using half of the built in UART on the 2051 for a serial lcd screen I have hooked up to it and the other half for an input only serial port (current plan is to hook up a serial barcode scanner). However, I want to have a second full serial port to communicate with a computer.

Since the 2051 only has one built in UART, it leaves me with a choice of either getting an external UART chip or doing a software UART. I'm already using 9 I/O lines of the 20 pin 2051 for a keypad and a LED, so I don't think I can use an external chip as I only have a few lines left. This leaves me with setting up a software UART.

I've never written code for a software UART and currently not sure how to implement it for my situation. As you know, I'm already using the built in UART and I'm also using one timer for a simple scheduler (which currently just scans the keypad, but I might add more to this later) and the other timer for the built in UART. I also currently know very little assembler (that'll change soon :-), so I'd need to do this in C. Can anyone help guide me in implementing this software UART?

Thanks,
J Silverman