CCS USART SETUP --> 16F877A

[sysysy]

Hi,

I'm planning to make a communication between 2 microcontroller with using RF transmitter and receiver (315Mhz).

So with USART, the data just will be put in the tx MCU1 and through the RF transmitter and in another side rx in MCU2 will receive the data.

There is a problem raise in my mind,
Do need method still need a rs232? I feel that it is don't need, but I just wonder when talk about USART, everybody talk about RS232. I'm really confusing with this?

Besides, any hint with writting the USART using CCS? Any built-in function. Else, how to set the USART register? I would happy if anyone willing to provide me some sample code.

Thanks alot.

Regards,
sysysy

[temtronic]

Whether you need RS232 interface chips(ie: MAX232) depends upon the RF transmitter / receiver modules you're using. Same are 'TTL' compatible, others need RS232 chips.
Be very careful with VOLTAGE supplies though, be sure both PIC and your xmt/rcv modules are compatible(both 5 v or both 3.3 volt)

CCS has several builtin functions for 'RS232' communications AKA serial interfaces, consult the help files as well as examples folders for info.

I suggest you get your program working without RF modules first, then add the modules later....

[sysysy]

[sysysy]

Hi,

I need a help from you guys.
Anyone know how to write the setup code for USART without RS232?

I found that all the ccs built-in also involving #use232(...). I don't know how to apply this in my case since I am not using rs232.

In my hardware, I never use rs232 or max 232, the communication just between 2 MCU through RF module. But before proceed to further RF communication, I want to try just using the jumper to connect Tx and Rx to test first.

But now I am stucking in writing the setup code. Hopefully anyone can provide me a sample setup code. Thanks.

[Ttelmah]

Funnily enough 'well done', in being confused.....

CCS, uses the nomenclature 'RS232' (which a PIC cannot generate without external buffer hardware), to refer to the async TTL serial which the chip generates. That the chip _doesn't_ actually generate 'RS232' communications leads sometimes to a lot of bother...
So the line #USE RS232, is used to setup the async hardware or software serial communication, even when 'RS232' is not involved. If (for example), you look in the RS485 examples (which obviously use 485, rather than 232 connections), they still use #USE RS232.
So in your case, you want this async serial connection, so use the #USE RS232 setup, and use the TTL serial to talk to your radio modules.

Best Wishes

[sysysy]

Thanks for the fast reply.

Hmmm, so in the #use232(...)

example

[Ttelmah]

Distinguish two configurations:
1) Setting up the hardware USART.
2) Generating a software UART emulation.

For '1', you 'need' the baud rate, the chip defaults to 8bits no parity (and the compiler does the same), so use:

#use rs232(baud=9600, UART1, ERRORS)

You don't need to specify the TX, and RX pins, since you are using the hardware UART (UART1 says this), but _do_ have the ERRORS statement (this adds code to handle UART overrun, and framing errors, and _must_ be used with the hardware, unless you do this yourself).

Stream is only necessary if you are setting up multiple connections.

For '2', you need to define the pins.

Best Wishes

[sysysy]

Hello,
i know i am weak in programming, this is just a only code that i can come out with. i don't know how to transmit and receive part.

I just want to simply send a signal from MCU1 to MCU2 while push the turn
on and off button. Then in other side, the LED will turn on when receive the signal.

I hope someone can help me complete my code. I know it is easy, but i don't know write the code to transmit out the data and receive data.

Transmitter Part

[ezflyr]

Hi sysysy,

You really need to spend a bit of time reading the forum, and studying the example programs. I'm a self-taught "C" programmer, and I did that by taking on some small projects that interested me, looking at the work of others, and experimenting. It's not terribly difficult, and can actually be a lot of fun to "learn by doing"!! If your programming "strategy" is to throw yourself at the mercy of the forum, I think you are going to be awfully disappointed with the results in the long run....!

Your code has a lot of problems. First, in the transmitter code, you are not debouncing your pushbuttons, and this will surely lead to problems. Look at the 'button' routine that has been posted here previously to do this. Next, your serial transmit syntax, Tx = On;, is meaningless. Take a look at the 'PUTC' function for sending individual bytes of data (ie. PUTC(0xAA);).

In the receiver code, look at the 'GETC' function. This function will allow you to receive a single character from the defined serial port.

Good Luck,

John