I am using a transceiver [TFDU4101-TR3](http://www.vishay.com/docs/81288/tfdu4101.pdf) to communicate with another device which has exactly the same transceiver. I bought this thinking I can communicate with the transceiver using my microcontroller ATMega164PA running at 8MHz at 3.3V. Turns out I cannot use serial without the endec which I cannot buy because of budget constraints.

So I was looking to use the RxD and TxD pins on the transceiver to somehow modulate the signal. I have made my PCB ages ago and the transceiver connects to the microcontroller through RX and TX lines. Can I still modulate the signal using RX and TX pins on the micro as GPIOs? 

I was looking into pulse width modulation but for that do I need to connect the transceiver pins to OCxA and OCxB pins on the micro? Can I still make do with RX and TX pins on the micro used as GPIOs and somehow use that in conjunction with PWM?