NOTE: This is the same setup as the last exercise “Potentiometer and LEDs”. The potentiometer is no longer necessary to the circuit but can remain in place without interference.

Plug the NXT sound sensor (microphone) into sensor port 2 0n the NXT.

• 220 Ohm Resistor (6)

• 10k Potentiometer (1)

• LED (6)

The six LEDs are connected to six digital-out pins. As the volume varies between 0% and 100% of the sensor's range, it outputs a value between 0 and 100. This value is read in the same algorithm as analog input A0 was read before and the amount of lit LEDs corresponds to the output of the sensor. This digital-out pin control can be realized in the code excerpt below:

...
 if(inputdata>20)  outputdata=b0|b1;
 if(inputdata>40)  outputdata=b0|b1|b2;
 if(inputdata>60)  outputdata=b0|b1|b2|b3;
 if(inputdata>80)  outputdata=b0|b1|b2|b3|b4;
 if(inputdata>90)  outputdata=b0|b1|b2|b3|b4|b5;
...

Circuit Diagram from HiTechnic's Experimenter's Kit Handbook

Photo of completed circuit

Note: If the video doesn't work just reload the page.

MicLED.nxc

/*
Filename: MicLED.nxc
Based on HiTechnic Experimenter's Kit Program
 
(c) HiTechnic 2009
(c) Alex Alspach 2012
 
*/
 
#include "NXCDefs.h"
 
#define PROTO_PORT IN_1
 
int inputdata;
int outputdata;
int count;
byte cmndbuf[];                 // buffer for outbound I2C command
byte respbuf[];                 // buffer for inbound I2C response
 
/* protoboard I/O map
   42,43 - A0 input
   44,45 - A1 input
   46,47 - A2 input
   48,49 - A3 input
   4A,4B - A4 input
   4C    - B inputs
   4D    - B outputs
   4E    - B controls
*/
 
void readdata()
  {
  ArrayInit(cmndbuf, 0, 2);     // set the buffer to hold 2 values
  cmndbuf[0] = 0x02;            // set write to channel
  cmndbuf[1] = 0x42;            // to set read address
  count=2;                      // 2 bytes to read
  I2CBytes(PROTO_PORT, cmndbuf, count, respbuf);  // issue I2C write command and read the byte back
  inputdata=respbuf[0]*4+respbuf[1];              // create input value by reading the high order byte,
                                                  // shift it left 3 bits and add the low order byt to
                                                  //create a full 10 bit value
  }
 
void writedata()
  {
  ArrayInit(cmndbuf, 0, 3);     // set the buffer to hold 3 values
  cmndbuf[0] = 0x02;            // set write to channel
  cmndbuf[1] = 0x4D;            // to set write address
  cmndbuf[2] = outputdata;      // to set write data
  count=0;                      // no bytes to read
  I2CBytes(PROTO_PORT, cmndbuf, count, respbuf);  // issue I2C write command and read the byte back
  }
 
task main()
  {
 
  byte b0 = 1;
  byte b1 = 2;
  byte b2 = 4;
  byte b3 = 8;
  byte b4 = 16;
  byte b5 = 32;
 
 
  int soundSensorValue;
  string stgSoundSensorValue;
  string stgMessageandValue;
 
  SetSensorSound(IN_2);
 
  SetSensorLowspeed(PROTO_PORT); // set sensor port 1 to low speed serial (I2C)
  Wait(100);
 
 
  ArrayInit(cmndbuf, 0, 3);     // set the buffer to hold 3 values
  cmndbuf[0] = 0x02;            // set write to channel
  cmndbuf[1] = 0x4E;            // to set write address
  cmndbuf[2] = 0x3F;            // to write 111111
  count=0;                      // no bytes to read
  I2CBytes(PROTO_PORT, cmndbuf, count, respbuf);  // issue I2C write command
  Wait(100);
 
  while (TRUE)
    {
 
    soundSensorValue = Sensor(IN_2);
    inputdata =  soundSensorValue;
 
    ClearScreen();
 
    NumOut(20, LCD_LINE1, inputdata);
 
    outputdata=b0;                      //set the output value to turn one LED on
    if(inputdata>20) outputdata=b0|b1;     //       based on the input value
    if(inputdata>40) outputdata=b0|b1|b2;
    if(inputdata>60) outputdata=b0|b1|b2|b3;
    if(inputdata>80) outputdata=b0|b1|b2|b3|b4;
    if(inputdata>90) outputdata=b0|b1|b2|b3|b4|b5;
    writedata();
 
    Wait(50);
    }
 
    StopAllTasks();
}

micled.zip