data communication using radio

Community Projects
1

Hello there,

  1. I have a VHF radio that can transmit data.

  2. Radio follows RS232 protocol to recieve and transmit data.

  3. I have purchased a gps bee which gives TTL output.

  4. I tried converting the TTL to RS232 using max232(which is working fine ,since checked using response of sim900 rs232) but when I recieve data on another radio and see it on Putty/Realterm , it is just garbage/corrupt data.

  5. Please advice where am i going wrong.

thanks in advance

2

Edit: Sorry, I read “gsp bee” and thought you were using Xbees.

VHF radios can’t communicate with XBees, unless they use Xbee frequencies and Xbee radio protocols (extremely unlikely).

Use two Xbees.

3

hello there,

ok i will put it like this.

please help me out in converting a ttl input to an rs232 one but of voltage ±12 V,because what i am getting from max232 cct is only ±9.5 V and that is not sufficeint for my project.

thanks in advance

4

The RS232 standard permits voltages compatible with what you are seeing with the max232.

Check data polarity inversions from end to end. Probably one inversion in the Max232.

5

but isnt max232 suppose to give proper inverted inputs.

can i make any other cct to convert ttl to ±12v rs232

6

+/-9.5V is well within the RS-232 specification. Don’t call it RS-232 if that is not what you want.

https://en.wikipedia.org/wiki/RS-232

7

please tell how can i further increase the voltage to ±12 v after they get converted to ±9.5 v by max232

8

tyaginitish1448:
please tell how can i further increase the voltage to ±12 v after they get converted to ±9.5 v by max232

One way to get that is to use +/- 12v power supplies and a a driver such as the MC1488. However, with 12v supplies the TI MC1488 max output is spec'd at only +/- 10.5v. That's only a volt more than the MAX232 outputs. As darelg said, this is well withing the RS-232 specs. RS-232 levels can be as low as +/- 3v. So I don't think that the voltage level is your problem.
9

@tyag

What happens if you connect the “rs232” transmitter to any other “rs232” comm (e.g. PC com output) and try to receive it on the “rs233” receiver? I’m thinking u still get garbage (which would indicate the xbee module is not the issue). If you do this and do not get garbage, does the “rs232” radio support the baud rate coming out of the xbee module?

10

i understand that the voltage level given with max232 are well with in rs232 levels ,but what about the amount of current required to drive the cct ahead. the amount of current generated by max232 might not suffice for the cct ahead ,thats why garbage is being recieved ,so please tell me a way by which i can increase the current in the signal.

thanks in advance