Tico,
I have used those modules in a project last fall. Be prepared for some head scratching. These modules do have "potential" but the manual leaves a lot to be desired. I spent nearly a week of hair pulling and lots of web searching before I got the thing to work. My boss was quite pissed about that! I contacted Sparkfun, the original distributor, and the guy at DOSONCHIP and they were both quite aware of the inacuracies of the manual and even today their website claims to be updating it in January of 2007. Here it is April 2007. I talked to those folks in October and they seemed almost unconcerned that the device was a bitch to work with and the manual was confusing. And I've got over 25 years experience in electronics.
I don't get it!
I was stuck because I had already designed the PCB for 13 units and had all the other parts ready to go. I did figure it out and used it but it was a pain. They have one advantage over the competition and that is the small footprint.
I don't have all my notes with me but here are some things from memory.
The reset pin can't be left unconnected as mentioned in the manual. Also if memory serves, the CTS line active state is reversed.
The command for writing is the most criptic thing I remember. When you send the command for write, you follow it with the number of bytes you intend to send. The module sends the quote character back to you and then you follow with the actual bytes. There is no way I could have deciphered that from the manual. I got that info from another "hair puller" on the internet.
My advice to you is to hook the thing up on a breadboard and practice using it with Hyperterminal before you even think of using it with your microcontroller. I did that so I could actually see what the thing was doing.
Good luck.
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