A how-to on making a DIY RS232 to TTL converter by Jestine Yong:
As I read many pages on the internet I saw there is a sort of adapter so called “USB to TTL adapter” who can communicate through with the uC. I had not the time to order one but I give a try to make one for the COM port. Actually it is an RS232 to TTL converter which I found better from my opinion than that USB to TTL adapter.
Here is why I like more this RS232 to TTL adapter than the other one:
- can be used on a real RS232 port
- it is a stable voltage level converter
- can be used on USB port too (through USB to RS232 converter)
- there is no VCC ( somebody would say it’s a disadvantage but wait…) *
- it is a real hardware stuff, no emulation etc. (if it is used through a real com port)
- can be built really cheap and easy
More details at Electronics Repair site.