Arduino Nano ATMega328 i2C raspberry Pi L298N Motor Driver Control

Projects Programming
1

Hi;

I have successfully built a collision avoidance robot using an Arduino Nano AtMega328, HC-SR04 Sensors, 9gMicro Servo (for scanning) and 2 x DC Motors connected via an L298N Motor Driver.

I am now trying to add a raspberry Pi connected via i2C to control the motors through the Nano, run a Webcam and stream video to a web page that will also be used to control the robot.

I have successfully interfaced the Arduino as Slave using i2C and have managed to blink the onboard LED using python on the raspberry Pi.

I have also managed to (finally) spin the motor connected to the L298N again using a Python command on the Rapsberry Pi.

At first I was having no joy but found that this was because I had been using some of the the Nano PWM as OUTPUTS, when using Sketch without the Pi via i2C on the original bot this was not a problem but when using i2c it seems it may be?

What I am having trouble with is using PWM commands and reading pin status (I keep getting a key error).

My Fault Finding

When I connected up an LED using a 1K resistor connected to pin 3 on the Nano, the LED blinked very momentarily and very dim. I then tried a 470ohm resister and got the same results.
When I looked at the pin status being returned, instead of High it showed a status of P?

Then I checked the pinouts again for the Nano, looking at this page:

http://eezone.co.uk/blog/arduino/arduino-compatible-nano-board-free-usb-cable-2.html

Pin 3 is also PWM so maybe setting the status of this pin to OUTPUT and High makes it PWM only??

I then amended the code and changed the wiring to use non PWM pins for the L298N inputs and a PWM for the L298N en pin.

First I tried using a PWM command with no joy, then I tried just to set the L298N en pin to High and when I ran the code Ta Da, the motor span :slight_smile:

So maybe when in i2C mode you can't use PWM pins as standard OUTPUTS to the 'in' pins on the L298N??

I still don't know the correct command for PWM to control the speed???

Here was my code not using PWM using pins that had worked fine on the avoidance bot:

Pinouts for the code below are:
Nano - L298N
08 - in1
07 - in2
11 - enA

There are two motors connected to pin 1 and 2 / 13 and 14

setPin(33, "08", "Output")  #on Arduino with I2C ID #33 set pin 08 to OUTPUT
setPin(33, "07", "Output")  #on Arduino with I2C ID #33 set pin 07 to OUTPUT
setPin(33, "11", "Output") #on Arduino with I2C ID #33 set pin 11 to OUTPUT
writePin(33,"08", "Low")   #on Arduino with I2C ID #33 set pin 08 LOW
writePin(33,"07", "High")   #on Arduino with I2C ID #33 set pin 07 HIGH
writePin(33,"11", "High")   #on Arduino with I2C ID #33 set pin 11 HIGH
# analogWritePin(33, "11", 245): #on Arduino with I2C ID #33 set PWM on pin 11 to 245

And here is the same code but this time trying to use a PWM analogueWritePin command:

setPin(33, "08", "Output")  #on Arduino with I2C ID #33 set pin 08 to OUTPUT
setPin(33, "07", "Output")  #on Arduino with I2C ID #33 set pin 07 to OUTPUT
setPin(33, "11", "Output") #on Arduino with I2C ID #33 set pin 11 to OUTPUT
writePin(33,"08", "Low")   #on Arduino with I2C ID #33 set pin 08 LOW
writePin(33,"07", "High")   #on Arduino with I2C ID #33 set pin 07 HIGH
# writePin(33,"11", "High")   #on Arduino with I2C ID #33 set pin 07 HIGH
analogWritePin(33, "11", "245"): #on Arduino with I2C ID #33 set PWM on pin 11 to 245

I then changed the pins for one motor and used:

Nano - L298N
4 - in1
7 - in2
3 - enA

By amending the first set of code above (setting pin 3 High and not using PWM) the motor span, trying the second set of code, again amended for the above pin changes and using a PWM command the motor failed to spin.

I am also still getting pin status read error:

2

And here is the code I am using to set the Arduino as slave and receive commands from the Pi.

// Arduino I2C Wire Slave version 0.21
// by Racer993 <http://raspberrypi4dummies.wordpress.com/>

// Turns the Arduino to a I2C slave device (for the Raspberry Pi) 
// using the Wire library. Configure pins, read and write to pins
// via a simple instruction set.

// Supported instructions
// pinMode = setPin(device, pinnumber, INPUT/OUTPUT/INPUT_PULLUP)
// digitalWrite = writePin(device,pinnumber,HIGH/LOW)
// analogWrite = analogWritePin(device,pinnumber,0-255)
// getStatus(device)

// A0 - analog read / digital write
// A1 - analog read / digital write
// A2 - analog read / digital write
// A3 - analog read / digital write
// A4 - IN USE as SDA
// A5 - IN USE as SCL

//  1 - digital read / write + RX
//  2 - digital read / write + TX  + Interrupt
//  3 - digital read / write + PWM + Interrupt
//  4 - digital read / write
//  5 - digital read / write + PWM
//  6 - digital read / write + PWM
//  7 - digital read / write
//  8 - digital read / write
//  9 - digital read / write + PWM
// 10 - digital read / write + PWM + SPI - SS
// 11 - digital read / write + PWM + SPI - MOSI
// 12 - digital read / write +       SPI - MISO
// 13 - digital read / write + LED + SPI - SCK

// HOW TO USE

// sending commands

// general: all commands must be 7 bytes long + 1 ending byte

// 1) to set the pinMode write a message with 7 characters on I2C bus to the arduino
// first character = S for set pinMode
// second & third character are pin ID 00 - 13 for digital pins & A0 - A3 for analog pins
// fourth character is to set the mode I for INPUT, O for OUTPUT, P for INPUT_PULLUP
// character 5,6,7 are not used, set to 000

// 2) to turn the pin on or off write a message with 7 characters on I2C bus to the arduino
// first character = W for digitalWrite
// second & third character are pin ID 00 - 13 for digital pins & A0 - A3 for analog pins
// fourth character is to turn off or on H for HIGH and L for LOW
// character 5,6,7 are not used, set to 000

// 3) to turn use PWM write a message with 7 characters on I2C bus to the arduino
// first character = A for analogWrite
// second & third character are pin ID 00 - 13 for digital pins & A0 - A3 for analog pins
// forth character is not used, set to X
// fifth - seventh character are used to write the PWM cycle (000-255)

// 4) to get a status with pin readings send Wire.requestFrom(device, #chars = 30)
// the arduino will send back 30 chars 
// char 1-14 for each digital pin 1 = on 0 = off
// char 15-18 for reading of A0, 1000 is added to the A0 reading in order to guarantee a 4 digit reading, subtract 1000 to get the proper reading
// char 19-22 for reading of A1, 1000 is added to the A0 reading in order to guarantee a 4 digit reading, subtract 1000 to get the proper reading
// char 23-26 for reading of A2, 1000 is added to the A0 reading in order to guarantee a 4 digit reading, subtract 1000 to get the proper reading
// char 27-30 for reading of A3, 1000 is added to the A0 reading in order to guarantee a 4 digit reading, subtract 1000 to get the proper reading

// Created 17 July 2013

// This example code is in the public domain.

#include <Wire.h>

void setup()
{
  int arduinoI2CAddress = 33;     // set the slave address for the Arduino on the I2C buss
    
  Wire.begin(arduinoI2CAddress); // join i2c bus with specified address
  Wire.onRequest(requestEvent);  // register wire.request interrupt event
  Wire.onReceive(receiveEvent);  // register wire.write interrupt event
}

  char sendStatus[31] = "000000000000000000000000000000";  // initialize the container variable
  int index = 0;                                           // initialize the index variable
  char pwm[15] = "00000000000000";                         // initialize the PWM flag container

void loop()
{
  
  String pinStatus="";                                      // initialize pinStatus variable
    
  for(int digitalPin = 0; digitalPin <= 13; digitalPin++)   // loop through 14 digital pins 0 - 13
     {
      if (pwm[digitalPin] == 0)                            // in case PWM is off for the pin, read the pin status
         {
           pinStatus += String (digitalRead(digitalPin));   // read the pin status & add it to the container variable
         }
      else
         { 
           pinStatus += "P";                                // in case PWM is on for the pin, add P to the pin status container string
         } 
     }
  
  for(int analogPin = 0; analogPin <= 3; analogPin++)      // loop through the 4 (unused) analog pins 0 - 3
     {
      pinStatus += String (1000+analogRead(analogPin));    // read the analog value from the pin, add 1000 to make it 4 digit & add it to the container variable
     }  
  
   pinStatus.toCharArray(sendStatus, 31);                  // convert the container variable pinStatus to a char array which can be send over i2c
    
  delay(1000);                                             // wait for an interrupt event
}

//--------------------------------------------------------------------------------
// function that executes whenever a status update is requested by master
// this function is registered as an event, see setup()

void requestEvent() { 
   Wire.write(sendStatus[index]);
    ++index;
    if (index >= 30) {
         index = 0;
    }
 }

//--------------------------------------------------------------------------------
// function that executes whenever a message is received from master
// this function is registered as an event, see setup()

void receiveEvent(int howMany)
{
  int receiveByte = 0;                   // set index to 0
  char command[7];                       // expect 7 char + 1 end byte
  String mode = "";                      // initialize mode variable for holding the mode
  String pin = "";                       // initialize pin variable for holding the pin number as a String
  String awValue = "";                   // intitalize the variable for holding the analogWrite value
  int pinVal;                            // inititalize the variable for holding the pin number as integer
  int awValueVal;                        // initialize the variable for holding the analog write value as integer (only PWM pins!)   
    
  while(Wire.available())                // loop through all incoming bytes
  {
    command[receiveByte] = Wire.read();  // receive byte as a character
    receiveByte++;                       // increase index by 1
  }
  
  pin = String(command[1]) + String(command[2]);                          // combine byte 2 and 3 in order to get the pin number
  awValue = String(command[4]) + String(command[5]) + String(command[6]); // combine byte 5, 6 and 7 in order to get the analogWrite value
  awValueVal = awValue.toInt();                                           // convert the awValue string to a value
  
  if (String(command[1]) != "A" ) { pinVal = pin.toInt();}                // in case of not an analog pin assignment convert into digital pin number
  if (String(command[1]) != "A" ) { pwm[pinVal] = 0;}                     // in case of not an analog pin assignment set PWM flag to 0

// incase of analog pin assignment determine analog pin to be set  
  if (String(command[1]) == "A" && String(command[2]) == "0") { pinVal = A0;}
  if (String(command[1]) == "A" && String(command[2]) == "1") { pinVal = A1;}
  if (String(command[1]) == "A" && String(command[2]) == "2") { pinVal = A2;}
  if (String(command[1]) == "A" && String(command[2]) == "3") { pinVal = A3;}

// if requested set pinmode  
  if (String(command[0]) == "S" && String(command[3]) == "I") { pinMode(pinVal, INPUT);}
  if (String(command[0]) == "S" && String(command[3]) == "O") { pinMode(pinVal, OUTPUT);}
  if (String(command[0]) == "S" && String(command[3]) == "P") { pinMode(pinVal, INPUT_PULLUP);}

// if requested perform digital write
  if (String(command[0]) == "W" && String(command[3]) == "H") { digitalWrite(pinVal, HIGH);}
  if (String(command[0]) == "W" && String(command[3]) == "L") { digitalWrite(pinVal, LOW);}


// if requested perform analog write
  if (String(command[0]) == "A" && pinVal == 3 || pinVal == 5 || pinVal == 6 || pinVal == 9 || pinVal == 10 || pinVal == 11 ) 
      { 
       analogWrite(pinVal, awValueVal);
       pwm[pinVal] = 1;
      }
  
}
3

Just had a reply on another forum which pointed to this link about coding PWM in Sketch:

Linky Link

I then spotted the line that says "You do not need to call pinMode() to set the pin as an output before calling analogWrite()".

This may have been causing the problem?

Still unsure about the key error?

4

Still not working :frowning: