Sending '+++' to serial port

[Andaluz]

OS: Linux Debian Lenny
IDE: Code::Blocks

Hello guys,

I really have an issue with sending '+++' to a GSM module through serial port. All the other AT commands are sent successfully, except that damn '+++'. This triple '+' is needed to tell the GSM module to bridge so the data is passed to another serial port device.

How am I sure that other AT data is sent successfully? Well, because for every AT command I send, I receive a repsonse. Normally a '+++' sends back a response of another serial port device. I have tested it with minicom (a serial port app) and sending '+++' works ok there. But from a C program it's not working. I'm kind of desperate now, cause I don't know what's the problem.

Another thing to mention, it just doesn't send somehow. I don't think '+' has a special meaning.

I hope you guys can give me some good tips.
Thank you.

[Salem]

+++ has two meanings, depending on how quickly you send it.

Testing it "slow speed" using minicom, you get one answer.

From a program, it gets sent a lot quicker, and the meaning changes.

[Andaluz]

Thanks for your reply, but even slow sending didn't work.
This is rediculous, that's so wrong, what's the difference between a '+' character and alphabetical character? It's all data...I'm about having a heart attack here.

[tabstop]

Wild guess based on no evidence whatsoever:
make sure your quotes are right (i.e. sending '+' not "+" or '+++', which should give a warning anyway)

[Andaluz]

Thank you Thank you Thank you Thank you very much for your help guys!
Salem was right, adding some pauses between the '+' did indeed help to solve the problem!

Tabstop, you are right also, cause my latest modification was wrong. Well if I get desperate, my coding gets worse too because of frustrations. But I was working on a system which has no network connection for some reasons, so I couldn't copy paste the code here.

The problem in our organization is communication. A colleague had implemented the '+++' stuff in an embedded device, but didn't tell me that he needs a few hundreds ms to process another serial port event. Which means, if he gets the '+' too fast, he won't do anything.

I learnt another important lesson and your help is very valuable, thank you very much.

[Salem]

Modem AT Command Set
Hayes command set - Wikipedia, the free encyclopedia
These talk about a pre and post delay. I'm not sure about the intra-character delay between each +

Anyway, good job on getting there.