Hi, can anyone help me to interpret what the code below is saying?
void chk_incoming() // incoming fuction call...
{
if ( radio.available() ) // check if a payload came in....
{
// Dump the payloads until we've gotten everything
bool done = false;
while (!done)
{
// Fetch the payload,
done = radio.read( button_states, num_button_pins );
printf("Got buttons\n\r"); // for debugging
// takes recieved button state and toggles the correct led
int i = num_led_pins;
while(i--)
{
if ( button_states[i] )
{
led_states[i] ^= HIGH;
digitalWrite(led_pins[i],led_states[i]);
}
}
}
}
I especially don't get the part where it says "int i = num_led_pins" and then "while (i--)"
Below is the whole code where the section above is from:
/*
Copyright (C) 2014 Nathan Sobieck <nathan@sobisource.com>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
version 2 as published by the Free Software Foundation.
*/
/*
/ This Example uses the RF24 library written by J. Coliz @ https://github.com/maniacbug/RF24 ,
/ Write this same sketch to two different Nodes. upon power up it will place both nodes into receiving mode
/ and await a button press. When a button press is detected it will switch to send mode, uppdate the leds on
/ on other node and return to listening mode.
/ PINS: NRF24l01 UNO/328p Mega
/ CE 3 - 9 9
/ CSN 4 - 10 53
/ SCK 5 - 13 52
/ MOSI 6 - 11 51
/ MISO 7 - 12 50
/ IRQ 8 - n/a n/a
*/
#include <SPI.h>
#include "nRF24L01.h"
#include "RF24.h"
#include "printf.h"
RF24 radio(9,53); //CE,CSN uno=(9,10) mega=(9,53)
// Buttons: where and how many
const uint8_t button_pins[] = { 3 }; // you can add more seperated by comma i.e.. (3, 4, 5)
const uint8_t num_button_pins = sizeof(button_pins);//this just adds how many pins there are so they can be checked in succession later
// Leds: where and how many
const uint8_t led_pins[] = { 2 }; // you can add more seperated by comma i.e.. (3, 4, 5)
const uint8_t num_led_pins = sizeof(led_pins); // same as as above for leds
// Single radio pipe address for the 2 nodes to communicate. in this case were just havining them take turns on the same address
const uint64_t pipe = 0xE8E8F0F0E1LL;
uint8_t button_states[num_button_pins]; // place to store button values
uint8_t led_states[num_led_pins]; // place to store led values
// Setup---------------------Setup---------------------Setup
void setup (void)
{
Serial.begin(57600);
printf_begin(); // starts printf.h so we can use it to print to serial monitor...
//you can replace all the printf("text"); stuff with Serial.println("text")
//but I like printf better than the built in serial.prinln as it has more options.
printf("Sobisource.com rf24 two way led test sketch %s\n"); // debug
radio.begin(); //starts nrf with whatever config settings have been set.
radio.setRetries(15,15);// optionally, increase the delay between retries & # of retries
radio.openReadingPipe(1,pipe); //opens preset pipe/channel for reading.
radio.startListening(); // starts listen on above pipe/channel
radio.printDetails(); // dumps the nrf settings to monitor for debugging
int i = num_button_pins; //
while(i--) //
{ // Sets buttons pins high
pinMode(button_pins[i],INPUT); // Looks for ground when pressed
digitalWrite(button_pins[i],HIGH); //
}
int L = num_led_pins; // Sets Led pins to on
while(L--) // till it recieves different info...
{ //
pinMode(led_pins[L],OUTPUT); // if you wanted them off till there turned on
led_states[L] = HIGH; // change HIGH to LOW
digitalWrite(led_pins[L],led_states[L]); //
}
}// end of setup=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Loop---------------------------Loop---------------------------Loop
void loop (void)
{
chk_incoming();
delay(20);
chk_outgoing();
} //end of loop-=-=--=--=--==-=--=--=-=-=-===-=-=--=-
void chk_incoming() // incoming fuction call...
{
if ( radio.available() ) // check if a payload came in....
{
// Dump the payloads until we've gotten everything
bool done = false;
while (!done)
{
// Fetch the payload,
done = radio.read( button_states, num_button_pins );
printf("Got buttons\n\r"); // for debugging
// takes recieved button state and toggles the correct led
int i = num_led_pins;
while(i--)
{
if ( button_states[i] )
{
led_states[i] ^= HIGH;
digitalWrite(led_pins[i],led_states[i]);
}
}
}
}
}
void chk_outgoing() // chk buttons states to see if we need to send updated info to other unit...
{
int i = num_button_pins;
bool different = false;
while(i--)
{
uint8_t state = ! digitalRead(button_pins[i]);
if ( state != button_states[i] )
{
different = true;
button_states[i] = state;
}
}
if (different)// if button has been pressed then.....
{
TX_mode(); //calls Tx_mode function
}
}
/* /
/ Tx_mode's code could have been placed directly above where "TX_mode();" /
/ was called but, I seperated it into it's own fuction for visual clairity and /
/ for easier editing later.. This sketch only uses like 7k space of the 30k on a uno /
/ so I wasnt too worried about saving space.... I also seperated it so it was clear how /
/ I did the switch from receiving to sending button states and back to receiving again..... /
*/
void TX_mode()// TX_mode function......
{
radio.stopListening(); // must stop listening before you open a writing pipe
radio.openWritingPipe(pipe);
printf("Now sending...",button_states, num_button_pins); // for debuggging info
bool ok = radio.write( button_states, num_button_pins ); // sends data
if (ok) { // checks if data was propperly received..
printf("ok\n\r"); // for debugging
radio.openReadingPipe(1,pipe); // closes writing pipe and opens Reading pipe
radio.startListening(); // sets listening mode so were receiving and we start all over again from the beginning...
delay(200);
}
else {
printf("failed\n\r"); // for debugging " lets you know other did not received transmittion "
}
}