RS232 Protocol not working

deltatech · Joined: 22 Apr 2006 Posts: 87

Hi I am trying to communicate with the following circuit . if you click on this link you can see it. www.geocities.com/knisar

The RS232 module works with following settings .

Speed 300
Data Bit Count 7
Parity Even, odd, mark, space
Stop Bit count 2

I have tried the following bit of code . But all i am getting on the monitor is a C .

Can any one please tell me what i am doing wrong .

grasspuddle · Joined: 15 Jun 2006 Posts: 66

what are you expecting to recieve?

it seems to me that it gets one char 'c' then hangs waiting to recieve another char.

for chars i usually use

deltatech · Joined: 22 Apr 2006 Posts: 87

according to the datasheet there should apear 15 ascii charecters when a o + cr is sent to the rs232 module . or the tx line is helh hich permentaly

deltatech · Joined: 22 Apr 2006 Posts: 87

grasspuddle i have tried but still i get a C on the monitor .

There should be 15 ASCII charecters mostly numbers .

Ttelmah · Guest

There are a whole series of seperate 'issues' here.
First,the PIC cannot generate 2 stop bits. If you need this, then you will have to set the data bits to 8, and 'pad' the characters with an extra '1' at the end.
Second, is this pin being used for the debugger or to talk to another unit?. You can't use the same pin for both operations, and if it is used for a debugger you still have to set both the transmit, and the receive pins (just to the same value).
Third, as has already been pointed out, '%s', is an incorrect printf declaration. This prints a _null terminated_ string. You do not have a null terminated string...
You speak of the unit sending 15 characters when an 'o' + CR is sent to it, but there is no sign of these characters being sent.
Though declaring a variable inside an internal routine, is acceptable in C, it is not really supported in CCS C. It may cause issues.

Best Wishes

deltatech · Joined: 22 Apr 2006 Posts: 87

I have corrected the code with fprintf(MSF,"%C",c); but still i only get a C on the monitor.

As pointed out by Ttelmah that the pins cannot be used for both the module and the monitor.

How do i get an indication if the module is sending data or not if i cant use the pins to display the output on the monitor.

Is is possible to talk to the RS232 module and display the data any other way . ?

Eugeneo · Joined: 30 Aug 2005 Posts: 155 Location: Calgary, AB

7bits+1parity+2stop = 10 bits

You're going to have to use the LONG_DATA (9data 1stop) with no hardare usart.