Communication rf adc

[sergio3214]

Friend what I want is to do the radio control for the electric cart that I build.
I want to make the servo motor control go right, center, and left
and an acceleration ramp for the traction motor.
And a button to reverse the motor direction forward or backward.

[temtronic]

As I said before, you can do ALL that without the RF modules. Build/code/test it all on the bench. Just 'simulate' the RF modules with 3 short wires to connect the PICs together.

I'd order 5 of the HC-12 modules and while waiting for them to arrive,code and test your program. That way you'll have working code when the HC12s come.
Then, simply add the HC12s (5 wires each) and your project is done.

Jay

[sergio3214]

"temtronic"Only you did not understand what I can not do in my code.

I want to control the bike but I can not do it, you could give me an example code so that it would be a guide for me, because until now I can only turn on the LED and the conversion, but I could not control the engine.

[Ttelmah]

Temtronic does understand. You need to actually start to write for yourself, and he is telling you how to start this more easily.

You need first of all to layout what your task needs to do. Probably send a number of 'messages' for different parts of the job.

So perhaps a 'button' message, and a 'steer' message.

Then you need to design the parts of these messages. Perhaps 'Bxc\n, where 'B' is the letter 'B', 'x' is a code for what button has operated, 'c' is a checksum, and `\n', is a line feed. Then perhaps 'Snnnc\n', again where 'S' is the letter 'S', 'nnn' is a number giving the steering position, 'c' is a checksum, and then again a line feed. Then your receive code, can look for the 'key' letters to know what to do with what follows, and when it sees the line feed, test the checksum, and if it is OK, then use the number to either say a button (or more than one button) has been pressed, or to set the steering to a position. You need to have a logic and design to your messages, so you can tell one from another, and verify that the message is correct before doing anything. The design needs to be yours, and suit what you need the messages to do.

Now, nobody is going to design this for you. Examples. There are hundreds of examples, both with the compiler, and here on the forum (and also some of the code library).

You need though also to understand the limitations. This is why I said to get a chip with a UART. Problem is that if your receive chip is going to do any sort of job 'with' the messages, if it doesn't have a UART, it will have to stop receiving to do the job. The UART helps to make it possible to actually do something with a received message, while the chip is receiving further messages.

Now, some comments on what you post:

1) The 12F675, doesn't have a UART. So it doesn't have an INT_RDA. This is what makes receiving hard on such chips....

2) Then assuming you switched to a chip with a UART, 'think microprocessor'. You are returning the data back to the sending chip (why?), using printf. The format you send back will 'print' the data as ASCII (so text a human can read). However much easier for a processor to receive, if you sent as (perhaps ) hex (then one character is four 'bits' of the number, without having to fiddle around. Also much easier if the data is sent is a 'fixed' width. So your 16bit value can be sent using the format %04X\n, and will then always be four characters wide, followed by a line feed. Makes receiving this _much_ easier and quicker to decode.

3) You have the comment:
"// characters transmitted faster than the pic eats them will cause UART to hang."
This is fundamentally wrong. The PIC will only transmit characters when it can. Won't hang. What will cause the UART to hang, is if characters are _received_ faster than they are read by the chip. Add 'ERRORS' to the UART setup (if you were on a chip with a UART....), to automatically prevent this.
Since neither chip you are using _has_ a UART, this doesn't apply anyway. All you will get if you miss a character is garbage.

Honestly if you are actually going to do anything with this data, you need a PIC with more pins. The 675, has 8pins. Two used by the power, two by the crystal. Using two more for TX/RX, only leaves two pins. Assuming you want to do anything at all with the data something larger is needed....
A PIC like the 16F1704, gives you 14 pins, and a UART. There are any number of more capable chips, but this is at least able to do what you are asking.
If you must use 8pin then the 12F1840, could be used without a crystal, and probably do what you are asking.

The second big reason nobody is answering your 'give me code' call, is that it is not really practical on your chip....

[sergio3214]

Good morning, Ttelmah.

Still can not develop the project, and my great difficulty is in the knowledge after all knowledge that I have acquired and through the internet, put this I could not leave the light and erase an LED through the communication, so ask for a sample code to follow as Base, I would like but a little of your help I know you can this me helping.

[temtronic]

As Mr. T points out, you've only got 2 available pins for 'control'.
1 could be the steering 'servo' assuming it's an RC model servo,
the other could be the 'traction motor', and IF I assume it's also an RC model style 'servo' motor, from a hardware perspective a 'possible' project.
The HUGE problem is software. Now it does have 1KW of program space so with very,very clever and careful coding you 'might' get it to work. The MAJOR probem is the communications functions. As pointed out, without a hardware UART a lot of code and time will be spent there.
As much as I love a challenge, I do not have the time to cut code for this.
However I would start by placing cart on blocks..
1) cutting code for the steering servo. RC servos generally respond like 1ms=left, 1.5ms=center, 2ms=right. So cut code to do that.
2) cut code for the traction motor. Without any specs of that, I'll assume an RC servo motor so 1ms=off, 1.5ms=1/2 speed, 2ms=full speed. Cut code and see what happens.
These tests can be in a loop that automatically does one 'command', pause for 2 seconds, then the next 'command'. Once you've confirmed it works, then step 3..
3) comunications. Design a 'protocol' to send data to the cart. Choose soemthing very simple, say 'L' for left, 'C' for center, 'R' for right, 'S' for stop, 'G' for go. Speed is difficult but you could use '1,2,3,4' as preset speeds, similar to gear shift selection. The key point is it needs to be simple as you don't have a lot of memory.
Once this all works on the bench, hardwired to a PC, then install the RF modems. If you use the HC-12 style, it'll work fine.

Jay

[sergio3214]

Ttelmah
I changed the microcontroller to pic18f252, that and my start code would like you to continue me helping to get control the motor
This is the transmitter code

[PCM programmer]

What temtronic and Ttelmah don't understand is that he can't write code.
He has said repeatedly "but I can not do it".

temtronic, he can't take your well-written description and turn it into code,
because he can't write code.

[sergio3214]

[gjs_rsdi]

Hi Sergio

You have written:

[sergio3214]

Good night!

I already wrote yes using MPLAB delivered ccs compile.
I have also done communication between two PICs, to turn on an LED.
What I want to control is a traction motor and a servomotor for a model
auto that I'm finishing.
This code was also the one I wrote.

[gjs_rsdi]

Hi Sergio

I hope you know that RCM servo actuators will work by pulse width modulation.
In general, you have to provide a pulse of 1000us for one side, 1500us for the middle and 2000us for the other side. The pulse may vary slightly per the manufacturer. The period is 20ms.
For the "traction motor" you need a electronic speed controller that works with pulses same as the servo. You have to buy a speed controller that fits the specific motor.
You should start writing code for the above PWM.

Regarding the program you posted, why you are using floats? It takes a lot of time to make them on those microcontrollers.
You can start from reading a potentiometer in 8 bit resolution as the command for the servo and generate the pulse accordingly.
Also working at 4MHz is giving you a 1us program cycle so your resolution for the pulse will be not so good. If working at 32MHz one PC=0.125us, 8 times faster.
By the way, PIC18F252 is not recommended by Microchip for new designs.

Best wishes
Joe

[sergio3214]

Good afternoon my friend enlarges balcony and I do not have enough skills and knowledge to write the code, all my knowledge and the base of the internet and the forum, so far only be able to make simple codes, with LED lighting, serial communication, unfortunately my knowledge Still and little for if you can only write the code in that size.

I thank you for the guidance and will be trying other code, until you reach this level of development.

[gjs_rsdi]

PCM Programmer is 100% right

[sergio3214]

GOOD NIGHT !!
Based on some research I wrote this code, it works but I can not send the data through the serial port, someone who can help me, and what I'm doing wrong