how to send and receive float for serial communication?

cenadius · Joined: 13 Mar 2010 Posts: 11

The ccs function for rs232 send and receive data can only use getc() and putc()?

If i want to send a float value or string, getc() and putc() seem can't be use for this purpose, is there any other function other than getc() and putc()?

I know there is a printf() to substitute the putc(), but if i use printf() then the getc() cant receive the exact value......

can any1 guide me?

thanks.

Wayne_ · Joined: 10 Oct 2007 Posts: 681

It depends if you want to send it in ASCII format or in binary ?

I like to just send the 4 bytes of the float and just re-build the float on the receiver but if you are sending to anything other than another pic you will have to re-arrange some of the bits.

cenadius · Joined: 13 Mar 2010 Posts: 11

Thanks for reply.

If I want to send in binary, how to convert it to binary and and convert it back to float at receiver?

Torello · Joined: 29 Sep 2006 Posts: 120

In a nut shell:

Create a struct with all your variables that you want to parse in each line that you send in your serial communication.
Receive the line in a buffer (int8 array), undo it from overhead information (like command and checksum (if there is)) and then memcpy the bare binary data in the struct variable. In this way each variable get typecasted and is directly accessible.
Of course you need to send the data in the right sequence according to the type of variables used.

I use this a lot to parse (UBX) data from a Gps module. I think is it a beautiful, easy way to do it.

Regards,
Edwin

Wayne_ · Joined: 10 Oct 2007 Posts: 681

Or

To send

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

Bravo Wayne_ !

A very clear simple example of C pointers in use. That is going in my (virtual) scrapbook.
_________________
The search for better is endless. Instead simply find very good and get the job done.

Ttelmah · Joined: 11 Mar 2010 Posts: 19538

Add one more comment to this thread.
In CCS C (for the PIC 12/16/18), the format of FP numbers in memory, is different from the IEEE format used inside a PC.
The file 'ieeefloat.c', contains two routines, to convert a PIC float directly to a PC float, and vice-versa.

So take Wayne's example, and modify as:

Gavin Pinto · Joined: 18 Oct 2009 Posts: 27 Location: Australia