Created a small RS232 Transceiver yesterday

On a current project we're working on, we had a serial port output which came from the BMC, but there was no RS232 to level shift the TTL levels. In this design, the RS232 transceiver is on the adjoining system which connects to this serial port.

So for testing purposes, to test this serial port we needed to either invest in a special cable with it all built in or make one ourselves from locally available parts. Unfortunately we weren't able to wait for the arrival from Farnell of the USB to TTL cable from FTDI (TTL-RS232-3V3). So I drove down to Maplin and picked me up a small Maxim RS232 transceiver (MAX3232CPE), 5 0.1uF ceramic disc caps and a male and female serial port header. Back in the labs, I snapped off a bit of unused bread-board, soldered in the part, cut the tracks beneath the device to isolate the pins on either side. Attached the 0.1uF caps, wires and I got 3V3 from the front of a capacitor on the actual system itself. Attached the thing up and lo and behold... it didn't work :(

I had the TX and Rx the wrong way around. I was using a crossover cable which swaps the Tx and Rx when going from my device to the Host PC. Once swapped, the yoke works proper. I haven't tested to see how clean the signals are yet, but it should work like a beauty.

The easy part was knowing where to hook up the caps and what to solder to where, it's all freely available on Maxim-IC's website MAX3222-MAX3241 DATASHEET (PDF).
See page 12 for the exact circuit I used. If using a different input voltage to 3V3, then check out table 2.