Category: Arduino

I ordered a Spark core post-Kickstarter. Interestingly, it shipped from Europe. Right out of the box, I could not get it to to connect to wifi (b/g). I tried configuring it by iOS app and by USB (cool!). It turns out that my ancient WAP54G was on channel 11. I changed the channel and it connected immediately. Weird.

I’ve used Electric Imps. I found them to be quirky and nearly impractical. The Imp cloud service is really hard to use. The API’s change a lot. The Imp would get stuck downloading new firmware and takes minutes to come back online after a hardware reset.

Want some quick starter code? Use this to control the built-in RGB LED.

void setup() {
RGB.control(true);
}

// wait one second
delay(1000);
}

I ran across this cheap (USD$4.70 SKU 250813) multi digit 7 segment display from DealExtreme. It’s composed of 3461BS displays and two 74HC595D shift registers. It runs cleanly on 5VDC (only voltage I tested). It requires three GPIO lines to run (latch, data, clock). Because the displays are multiplexed, it can only display one character at a time. This means you need to set activate each character faster enough to avoid any flicker (at least >= 20 hertz).

#define latch 9
#define clock 10
#define data 11
#define kDigitCount 8

char gDisplayBuffer[kDigitCount+1];

void setup()
{
   pinMode(latch, OUTPUT);
   pinMode(clock, OUTPUT);
   pinMode(data, OUTPUT);
   
   Serial.begin( 9600 );
   
   memset(gDisplayBuffer, ' ', kDigitCount);
}


void writeDigit(int digit, char inValue)
{
  byte value = 0;
  byte bitsToSend = 0;
  
  bitSet(bitsToSend, digit);
  
  digitalWrite(latch,LOW);
  shiftOut(data,clock,MSBFIRST, bitsToSend);
  
  
    switch (inValue)
    {
        case '.': value = B01111111; break;
        case '1': value = B11111001; break;
        case '2': value = B10100100; break;
        case '3': value = B10110000; break;
        case '4': value = B10011001; break;
        case '5': value = B10010010; break;
        case '6': value = B10000011; break;
        case '7': value = B11111000; break;
        case '8': value = B10000000; break;
        case '9': value = B10010000; break;
        case '0': value = B11000000; break;
        case 'H': value = B10001001; break;
        case 'i': value = B11111011; break;
        
        default:
        case ' ': value = B11111111; break;
    }
    
    shiftOut(data,clock,MSBFIRST,value);
  
  digitalWrite(latch,HIGH);
}

void writeToDisplay(bool inOveride)
{
  for (int i = 0 ; i < kDigitCount ; i++)
  {
    if (' ' != gDisplayBuffer[i] || inOveride)
      writeDigit(i, gDisplayBuffer[i]);
  }
}

void loop()
{
  char cmdBuffer[16];
  
  if (0 < Serial.available())
  {
      memset(cmdBuffer, ' ', 16);
      int iBytes = Serial.readBytesUntil('\n', cmdBuffer, 16);
      cmdBuffer[iBytes] = 0;
      
      if (!strncmp(cmdBuffer, "SET ", 4))
      {
        if (12 != strlen( cmdBuffer))
          Serial.println("ERR");
        else
          memcpy(gDisplayBuffer, &cmdBuffer[4], kDigitCount);
      }
      else if (!strncmp(cmdBuffer, "CLR", 3))
      {
          memcpy(gDisplayBuffer, "        ", kDigitCount);
          
          writeToDisplay(true);
      }
  }
  
  writeToDisplay(false);
}

I’m a big fan of Fridays, not just because the weekend is close, but Friday is the day SparkFun releases new products. I have a special box near my home work bench with all the breakout boards I’ve purchased through the past few years. I have a break board for almost every purpose. Even the chinese are seeing value in producing breakout boards for smaller SMD components. You can find a number of interesting modular pieces on ebay through other Hong-King storefronts.

The state of industry (and market demand) is now advanced enough that kits are being produced using several different breakout boards. Take for example the FabFM kit. It uses a SI4703 breakout board. Anyone could modify such a kit with extra features, but it also looks aesthetically pleasing.