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NRF24L01에 대한 공부를 하던 중 RF24 라이브러리를 설치하면 아두이노에 있는 예제 gettingstarted 를 공부하던 중 이해가 안가는 부분이 있어서 이렇게 글을 올리게 되었습니다.
하단에 코드 전부분을 일단 올려 놓았구요. NRF24L01을 공부하신 분이면 누구나 한번쯤 보셨을 코드라고 생각합니다. 원리는 간단한 것 같은데 제가 뭔가 기본적인 걸 모르는 것 같습니다.
byte addresses[][6] = {"1Node","2Node"}; 에서
byte란 -125~125 까지의 정수를 나타내는 데이터형이고 addresses[ ][6] 은 2차원 배열인 것으로 이해했습니다.
그런데 1Node, 2Node는 텍스트인데 정수형 데이터로 선언한 배열에 어떻게 문자가 들어가는 걸까요???
예를 들어
addresses[0][0] = 1
addresses[0][1] = N
addresses[0][2] = o
addresses[0][3] = d
addresses[0][4] = e
addresses[0][5] = " "
이렇게 들어간단 말입니까?
그리고 밑에 보면
radio.openWritingPipe(addresses[1]);
과 같이 위에서 선언하고 값을 넣어준 addresses 배열을 사용하기 시작하는데
2차원 배열이었던 addresses가 1차원 배열이 되어 버렸습니다.
대체 addresses[1]에는 무슨 값이 들어있을까 궁금하여
새 스케치 창을 열어 아래와 같이 실험을 했더니 컴파일시에 오류가 나버립니다.
-----------------------------------------------------------------------
int i;
byte addresses[][6] = {"1Node","2Node"};
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
}
void loop() {
// put your main code here, to run repeatedly:
Serial.println(addresses[1]);
}
------------------------------------------------------------------
컴파일 에러 메시지
exit status 1
call of overloaded 'println(byte [6])' is ambiguous
누구라도 좋으니 알려주시면 감사하겠습니다.
그리고 하나 더 있습니다.
radio.openReadingPipe(1,addresses[1]); 에서 괄호열고 바로 적혀있는 1이 무슨 의미인지도 알고 싶습니다.
알려 주시면 감사하겠습니다.
---------------------------------------------------------------------------
/*
* Getting Started example sketch for nRF24L01+ radios
* This is a very basic example of how to send data from one node to another
* Updated: Dec 2014 by TMRh20
*/
#include <SPI.h>
#include "RF24.h"
/****************** User Config ***************************/
/*** Set this radio as radio number 0 or 1 ***/
bool radioNumber = 1;
/* Hardware configuration: Set up nRF24L01 radio on SPI bus plus pins 7 & 8 */
RF24 radio(7,8);
/**********************************************************/
byte addresses[][6] = {"1Node","2Node"};
// Used to control whether this node is sending or receiving
bool role = 0;
void setup() {
Serial.begin(115200);
Serial.println(F("RF24/examples/GettingStarted"));
Serial.println(F("*** PRESS 'T' to begin transmitting to the other node"));
radio.begin();
// Set the PA Level low to prevent power supply related issues since this is a
// getting_started sketch, and the likelihood of close proximity of the devices. RF24_PA_MAX is default.
radio.setPALevel(RF24_PA_LOW);
// Open a writing and reading pipe on each radio, with opposite addresses
if(radioNumber){
radio.openWritingPipe(addresses[1]);
radio.openReadingPipe(1,addresses[0]);
}else{
radio.openWritingPipe(addresses[0]);
radio.openReadingPipe(1,addresses[1]);
}
// Start the radio listening for data
radio.startListening();
}
void loop() {
/****************** Ping Out Role ***************************/
if (role == 1) {
radio.stopListening(); // First, stop listening so we can talk.
Serial.println(F("Now sending"));
unsigned long start_time = micros(); // Take the time, and send it. This will block until complete
if (!radio.write( &start_time, sizeof(unsigned long) )){
Serial.println(F("failed"));
}
radio.startListening(); // Now, continue listening
unsigned long started_waiting_at = micros(); // Set up a timeout period, get the current microseconds
boolean timeout = false; // Set up a variable to indicate if a response was received or not
while ( ! radio.available() ){ // While nothing is received
if (micros() - started_waiting_at > 200000 ){ // If waited longer than 200ms, indicate timeout and exit while loop
timeout = true;
break;
}
}
if ( timeout ){ // Describe the results
Serial.println(F("Failed, response timed out."));
}else{
unsigned long got_time; // Grab the response, compare, and send to debugging spew
radio.read( &got_time, sizeof(unsigned long) );
unsigned long end_time = micros();
// Spew it
Serial.print(F("Sent "));
Serial.print(start_time);
Serial.print(F(", Got response "));
Serial.print(got_time);
Serial.print(F(", Round-trip delay "));
Serial.print(end_time-start_time);
Serial.println(F(" microseconds"));
}
// Try again 1s later
delay(1000);
}
/****************** Pong Back Role ***************************/
if ( role == 0 )
{
unsigned long got_time;
if( radio.available()){
// Variable for the received timestamp
while (radio.available()) { // While there is data ready
radio.read( &got_time, sizeof(unsigned long) ); // Get the payload
}
radio.stopListening(); // First, stop listening so we can talk
radio.write( &got_time, sizeof(unsigned long) ); // Send the final one back.
radio.startListening(); // Now, resume listening so we catch the next packets.
Serial.print(F("Sent response "));
Serial.println(got_time);
}
}
/****************** Change Roles via Serial Commands ***************************/
if ( Serial.available() )
{
char c = toupper(Serial.read());
if ( c == 'T' && role == 0 ){
Serial.println(F("*** CHANGING TO TRANSMIT ROLE -- PRESS 'R' TO SWITCH BACK"));
role = 1; // Become the primary transmitter (ping out)
}else
if ( c == 'R' && role == 1 ){
Serial.println(F("*** CHANGING TO RECEIVE ROLE -- PRESS 'T' TO SWITCH BACK"));
role = 0; // Become the primary receiver (pong back)
radio.startListening();
}
}
} // Loop
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