Realtime sending PWM values using 433Mhz transmitter - c++

Question

I have tried to create wireless PWM transmission using 433Mhz transmitter modules. I found this library for transmiting https://github.com/zeitgeist87/RFTransmitter and this library for reading PWM values on some pin https://github.com/xkam1x/Arduino-PWM-Reader.
I wrote code for sending PWM values:
#include "PWM.hpp"
#include <RFTransmitter.h>
#define NODE_ID 1
#define OUTPUT_PIN 11
RFTransmitter transmitter(OUTPUT_PIN, NODE_ID);
PWM my_pwm(2);
// the setup function runs once when you press reset or power the board
void setup() {
my_pwm.begin(true);
}
// the loop function runs over and over again forever
void loop() {
int pwmValue = my_pwm.getValue();
char stringValue[4];
itoa(pwmValue, stringValue, 10);
transmitter.send(stringValue, strlen(stringValue) + 1);
}
And similar code for receiving
#include <Servo.h>
#include <PinChangeInterruptHandler.h>
#include <RFReceiver.h>
int PWM_out_pin = 9;
Servo servo;
// Listen on digital pin 2
RFReceiver receiver(2);
void setup() {
servo.attach(PWM_out_pin);
receiver.begin();
}
void loop() {
char msg[MAX_PACKAGE_SIZE];
byte senderId = 0;
byte packageId = 0;
byte len = receiver.recvPackage((byte *)msg, &senderId, &packageId);
String *stringObject = new String(msg);
servo.writeMicroseconds(stringObject->toInt());
}
It works, but it has few problems.
First is that is not optimal. I transforming all to string. How can I send int values from PWM directly?
Second problem is that it has about 1 sec delay. Does it possible make it faster? I need it for realtime controlling servo.
Thanks.

Answer 1

How can I send int values from PWM directly?
transmitter.send((char*)pwmValue, sizeof(int));
Then on the receive side, you don't need to convert the data to a string.
servo.writeMicroseconds((int) *msg);
(int) and (char*) are C-style typecasts. Essentially telling the compiler that you want the data to be interpreted as a different variable type.
WARNING: Be careful with the "new" keyword, you are dynamically allocating memory. Rule of thumb in C/C++: Wherever you use the "new" keyword there should be a corresponding "delete" call that cleans up the memory.
In terms of making it faster, your C/C++ code here is not the limiting factor causing the 1 sec latency from command to action. Most likely there is a parameter in your RF transmitter transmit/receive stack that needs to be tweaked. Before sending PWM values, I would benchmark your latency of sending and printing out a simple string.