In this tutorial we learn how communicate between two Arduino using low cost 433MHz wireless modules. These modules are also available in long range in kilo meters. It uses ASK (Amplitude Shift Keying).
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In Arduino programming many times you will come with situations where you want to put double quotes in a string. For example sending AT command with double quotes. There many different methods let’s discuss one by one.
How do I put quotes in a string?
AT+CPMS=”SM”
Serial.println(“AT+CPMS=”SM””); // This results in error
Continue reading Arduino : How to put quotation marks in a string ?
A Serial Peripheral Interface (SPI) bus is a system for serial communication, which uses up to four conductors, commonly three. One conductor is used for data receiving, one for data sending, one for synchronization and one alternatively for selecting a device to communicate with. It is a full duplex connection, which means that the data is sent and received simultaneously. The maximum baud rate is higher than that in the I2C communication system.
SPI uses the following four wires −
The following functions are used. You have to include the SPI.h.
We have four modes of operation in SPI as follows −
Now, we will connect two Arduino UNO boards together; one as a master and the other as a slave.
The ground is common. Following is the diagrammatic representation of the connection between both the boards −
Let us see examples of SPI as Master and SPI as Slave.
Master unit sends hello world data to slave unit.
#include <SPI.h>
void setup (void) {
Serial.begin(115200); //set baud rate to 115200 for usart
digitalWrite(SS, HIGH); // disable Slave Select
SPI.begin ();
SPI.setClockDivider(SPI_CLOCK_DIV8);//divide the clock by 8
}
void loop (void) {
char c;
digitalWrite(SS, LOW); // enable Slave Select
// send test string
for (const char * p = "Hello, world!\r" ; c = *p; p++)
{
SPI.transfer (c);
Serial.print(c);
}
digitalWrite(SS, HIGH); // disable Slave Select
delay(2000);
}
Slave unit waits for data as soon as data is arrived process variable becomes true, indicating there is data in buffer. in main loop we read this buffer and send to serial terminal.
#include <SPI.h>
char buff [50];
volatile byte indx;
volatile boolean process;
void setup (void) {
Serial.begin (115200);
pinMode(MISO, OUTPUT); // have to send on master in so it set as output
SPCR |= _BV(SPE); // turn on SPI in slave mode
indx = 0; // buffer empty
process = false;
SPI.attachInterrupt(); // turn on interrupt
}
ISR (SPI_STC_vect) // SPI interrupt routine
{
byte c = SPDR; // read byte from SPI Data Register
if (indx < sizeof buff) {
buff [indx++] = c; // save data in the next index in the array buff
if (c == '\r') //check for the end of the word
process = true;
}
}
void loop (void) {
if (process) {
process = false; //reset the process
Serial.println (buff); //print the array on serial monitor
indx= 0; //reset button to zero
}
}
Open serial monitor of slave, you will see “Hello, World”.
Many new people find this error avrdude: stk500_getsync(): not in sync: resp=0x00 while uploading program to board.
Before we start to conclude the error first know how arduino works.
Arduino IDE is a special software running on your system that allows you to write sketches (synonym for program in Arduino language) for different Arduino boards. The Arduino programming language is based on a very simple hardware programming language called processing, which is similar to the C language.
In fact, you already are; the Arduino language is merely a set of C/C++ functions that can be called from your code. Your sketch undergoes minor changes (e.g. automatic generation of function prototypes) and then is passed directly to a C/C++ compiler (avr-g++).
Arduino board is basically consists of main three components.
In most cases program is uploaded using usb cable or using external usb to serial converter.
When u buy fresh micrcontroller such as ATmega328p from market. It is completely blank. To program using arduino you need USB-ASP (SPI based programmer) shown below.
Reason 1: You are trying to program using serial of arduino to a blank controller.
Flashing Arduino boot-loader to fresh ATmega328p.
After uploading bootloader you can use serial port / usb to program your arduino.
When using external USB2Serial converter, May be you have not connected +5V to microcontroller or Incorrect connections of Rx TX.
You have connected external device on Rx Tx pin i.e. Arduino Pin 0 and Pin 1.
Remove or Disconnect any circuit present on Rx Tx lines and try again.
You have selected incorrect Serial Port. Go to Tools>>Ports Menu and select proper port.
or Incorrect board selection.
If you will not find correct serial port, check that you have installed correct USB to Serial converter or Arduino Drivers. for windows look for any yellow sign (indicates error) on Serial ports.
For linux see this
Tools ► Board ►, e.g. If you are using the Duemilanove 328, select that instead of Duemilanove 128. The board should say what version it is on the microchip.Tools ► Serial Port ►. One way to figure out which port it is on is by following these steps:
Tools ► Serial Port ► and see which ports are listed (e.g. COM4 COM5 COM14).Tools ► Serial Port ►, and see which port appeared that wasn’t there before.Unfortunately, it can also mean that you burned your microcontroller. Were you doing anything dangerous right before you tried to upload a new sketch?
When using external USB to serial converter you need to connect RTS pin of usb2serial converter to reset pin of micro-controller through a 0.1uF (104) capacitor.
You need four pins from external serial converter RX, TX, GND and RTS —||— with 0.1uF capacitor connect one terminal of capacitor to RTS pin and another to reset pin of micro-controller.
Try running Arduino IDE in administrator mode.
Check that Most of the Arduino boards use 16MHz or 8MHz crystal, If you are trying with fresh chip, this is common mistake. Use 16MHz crystal for ATmega328p with Arduino UNO boot-loader
These are the most common mistakes that cause error avrdude: stk500_getsync(): not in sync: resp=0x00
In this tutorial we interface RCWL-0516 Human body induction switch module Intelligent sensor (Radar Motion sensor) with Arduino.
This mini doppler radar motion sensor module is equipped with supporting DC 4-28V wide voltage. It will automatically continuously output the high level TTL signal when there is motion. 360 degree no blind angle detection and maximum 7m sensing distance. It is perfect for DIY microwave motion sensor light switch, human sensor toys, smart security devices, etc.
Continue reading RCWL-0516 Doppler Radar Sensor Interface with Arduino