[RESOLVED] First attempt at I2C

Comments

• Hal Albach Posts: 747

  2014-12-21 18:01 edited 2014-12-21 18:01

  I'm not 100% certain but I think the device address you are using is trying to address device 0x40. If the actual device address is 0x20 then the 7 bit address should be 0b0010000. Try using the 7 bit binary address instead of the variable sensorADDR and see if that works.
  I use the same I2C function in my projects and use 0b1010000 for the EEPROM (address 0xA0) and 0b1100000 for a compass (address 0xC0) and using the 7 bit binary for the device address it all works. The 7 bit address has bit 0, the R/W bit, removed.
  EDIT: I just modified my EEPROM code and defined a variable "int eeadr = 0b1010000; and the program continues to access the EEPROM. So if you change the variable sensorADDR assignment to 0b0010000 it should work.
• Wildatheart Posts: 195

  2014-12-21 18:54 edited 2014-12-21 18:54

  Revised address to 0b0010000 and removed the "!" from the "while busy" statement. Now value always = 0.
  
  I am suspecting the need for pull-ups on the SCL and SDA lines?
• Hal Albach Posts: 747

  2014-12-21 19:17 edited 2014-12-21 19:17

  Definitely put pullup resistors on the bus. Your first statement in Main() ;
  

    i2cBus = i2c_newbus(IRsensor_SCL, IRsensor_SDA, 0);            // Join the I2C bus master (Mode 0 indicates pull-up 
    print ("Joined master bus \n");                                //   resistors present on the SDA & SCL lines)
  

  The last parameter being 0 means that the I2C bus will have pullup resistors instead of the propeller I/O driving the bus high and low. The propeller does not provide the pullups in mode 0, you have to provide them. Actually, per the I2C Specification, pullups are required. I use 4.7K resistors and never have any problems. Just be sure to use 3.3 Volts as the pullup source, not 5 - keeps the prop happy.
  
  edit (again!) Just noticed you are using the PPDB, and the schematics indicate that it is using one 10K resistor as a pullup on the SDA (P29) line. Add a 10K to SCL line.
  Just looked up the device you are using and there seems to be some confusion re device address. The OSEPP site for the IR module clearly states the device address is 0x20, but the I2C interface chip on the module is a PCA9534, which, according to all data sheets shows a device address of 0b0100000.
  For the i2c_in statement, I would define a char variable at the beginning of main and use that variable name for the data field. Change "(char*)&val" to whatever name you use for the data variable.
  On the module the schematic shows two switches, A1 and A2, both need to be closed to keep the low nibble of the device address at 0.
• Wildatheart Posts: 195

  2014-12-22 12:18 edited 2014-12-22 12:18

  Sensor address appears to be 0b0010000 else attempts to use address 0b0100000 will cause the program to hang at the request to join the bus.
  
  Added 10K between 3.3V and SCL (pin 28) as recommended. Also renamed (char*)&val with a char variable as recommended. Still no go.
  
  But I have noticed that if I set val = 5 the loop will cycle and print the value received as 5. So among other possible problems the “i2c_in” is not functioning as intended.
  
  I’m guessing that memADDR or the parameters in “i2c_in” are not set properly.
• Hal Albach Posts: 747

  2014-12-22 13:02 edited 2014-12-22 13:02

  I found this sketch on their web site, it may provide some guidance as to the communications required, read the comments for the setup function to turn on the sensor . So, before you can read any data from the sensor you first have to write to it.
  

  IR Proximity Sensor Module
  Setup
  Connect one end of the cable into either Molex connectors on the sensor
  Connect the other end of the cable to the Arduino board:
  RED: 5V
  WHITE:  I2C SDA (pin A4 on Uno; pin 20 on Mega)
  BLACK: GND
  GREY: I2C SCL (pin A5 on Uno; pin 21 on Mega)
  Set the DIP switch on the sensor to set the sensor address (check back of sensor for possible addresses)
   
  Example Sketch
  // OSEPP IR Proximity Sensor Example Sketch
  // by OSEPP <http://www.osepp.com>
  
  // This sketch demonstrates interactions with the IR Proximity Sensor
  
  #include <Wire.h>
  
  // Possible sensor addresses (suffix correspond to DIP switch positions)
  #define SENSOR_ADDR_OFF_OFF  (0x26)
  #define SENSOR_ADDR_OFF_ON   (0x22)
  #define SENSOR_ADDR_ON_OFF   (0x24)
  #define SENSOR_ADDR_ON_ON    (0x20)
  
  // Set the sensor address here
  const uint8_t sensorAddr = SENSOR_ADDR_OFF_OFF;
  
  // One-time setup
  void setup()
  {
     // Start the serial port for output
     Serial.begin(9600);
  
     // Join the I2C bus as master
     Wire.begin();
  
     // Turn on the sensor by configuring pin 1 of the GPIO expander to be an
     // output pin; the default output value is already HI so there's no need
     // to change it
     WriteByte(sensorAddr, 0x3, 0xFE);
  }
  
  // Main program loop
  void loop()
  {
     uint8_t val;
  
     // Get the value from the sensor
     if (ReadByte(sensorAddr, 0x0, &val) == 0)
     {
        // The second LSB indicates if something was not detected, i.e.,
        // LO = object detected, HI = nothing detected
        if (val & 0x2)
        {
           Serial.println("Nothing detected");
        }
        else
        {
           Serial.println("Object detected");
        }
     }
     else
     {
        Serial.println("Failed to read from sensor");
     }
  
     // Run again in 1 s (1000 ms)
     delay(1000);
  }
  
  // Read a byte on the i2c interface
  int ReadByte(uint8_t addr, uint8_t reg, uint8_t *data)
  {
     // Do an i2c write to set the register that we want to read from
     Wire.beginTransmission(addr);
     Wire.write(reg);
     Wire.endTransmission();
  
     // Read a byte from the device
     Wire.requestFrom(addr, (uint8_t)1);
     if (Wire.available())
     {
        *data = Wire.read();
     }
     else
     {
        // Read nothing back
        return -1;
     }
  
     return 0;
  }
  
  // Write a byte on the i2c interface
  void WriteByte(uint8_t addr, uint8_t reg, byte data)
  {
     // Begin the write sequence
     Wire.beginTransmission(addr);
  
     // First byte is to set the register pointer
     Wire.write(reg);
  
     // Write the data byte
     Wire.write(data);
  
     // End the write sequence; bytes are actually transmitted now
     Wire.endTransmission();
  }
  - See more at: http://osepp.com/learning-centre/start-here/ir-proximity-sensor-module/#sthash.s7X5gwaf.dpuf
  
• Andy Lindsay (Parallax) Posts: 1,919

  2014-12-22 17:28 edited 2014-12-22 17:28

  Here is some code adjusted per posts to to this point. Sorry if it still doesn't work, I don't have this particular sensor to test. If it doesn't work as-is, retry with while(i2c_busy... and i2c_stop commented. Side note: 3 bytes per exchange is a good sign, but not a guaranty.
  

  /*
    Using PPDB:
    Test I2C OSEPP IR proximity sensor module 
        http://osepp.com/products/sensors-arduino-compatible/osepp-ir-proximity-sensor-module/ 
    SW1 and SW2 are shorted for address 0x20
    Assume master controller has pull-ups, therefore SB1 and SB2 are left open.  
        See PDF schematic at bottom of OSEPP web page.
  */
  
  #include "simpletools.h"                      // Include simpletools header
  
  i2c *i2cBus;                                  // I2C bus ID
  
  const int i2c_SCL = 28;                       // Propeller pin 28
  const int i2c_SDA = 29;                       // Propeller pin 29   
  
  const int irProx0 = 0x20;                     // Address 0x20 named irProx0
  
  int main()
  {
    i2cBus = i2c_newbus(i2c_SCL, i2c_SDA, 0);   // Declare I2C bus with pullups
                        
    int reg = 0x3;                              // Declare/init reg & data
    char data = 0xFE; 
    int b = i2c_out(i2cBus, irProx0, reg, 1,    // Turn on sensor
                                   &data, 1);
                                   
    print("Bytes sent = %d\n", b);              // Addr + reg + data = 3
  
    while(1)                                    // Main loop
    {
      while(i2c_busy(i2cBus, irProx0));         // Wait here if sensor is busy
      i2c_stop(i2cBus);                         // Might be needed
  
      reg = 0;                                  // Set reg to 0
      data = 0;                                 // Prepare data for new reading
      b = i2c_in(i2cBus, irProx0, reg, 1,       // Check irProx0 sensor
                                &data, 1);
  
      print("Bytes total = %d\n");               // Addr + reg out + data in = 3
  
      int val = (data >> 2) & 1;                 // Isolate detection bit
      if(b == 3) print("val = %d \n", val);      // Print detection status
      
      pause (500);                               // 1/2 sec before repeat
    }    
  }
  
• Wildatheart Posts: 195

  2014-12-23 06:48 edited 2014-12-23 06:48

  With Andy's example in #7... Bytes sent = 3. Bytes total = 3.
  
  int val = (data >> 2) & 1; needs to be changed to int val = (data >> 1) & 1;
  
  Example code works with or without i2c_busy and/or i2c_stop
  
  Andy, after your review of the changes one of us should pass this on to OSEPP to promote this sensor's use with the Propeller. Thanks Hal and Andy for your interest and help.