{"id":392,"date":"2008-07-06T11:05:43","date_gmt":"2008-07-06T15:05:43","guid":{"rendered":"http:\/\/mini.local\/blog\/index.php?entry=entry080706-110543"},"modified":"2008-07-06T11:05:43","modified_gmt":"2008-07-06T15:05:43","slug":"ir-interfacing-with-a-led-messgage-sign-part-2","status":"publish","type":"post","link":"https:\/\/biosrhythm.com\/?p=392","title":{"rendered":"IR interfacing with a LED messgage sign, part 2"},"content":{"rendered":"

\"\"<\/a>
To make the Arduino transmit IR signals, you need an IR LED. I found a couple from an old Sun optical mouse and an old TV remote control. I used two emitters because that's what the original Pro-Lite remote has inside and it also gains distance (I hoped). I should probably be connecting these LEDs through a resistor and at various stages I did. But I figured the pulses were so short that it _may_ be ok. Besides, there's more where that came from.<\/p>\n

I started the IR emitter sketch from this Arduino forum post<\/a>. Actually, the part that was most interesting, was how to modulate the LED at a certain frequency.

\/\/ this will write an oscillation at 38KHz for a certain time in useconds
void oscillationWrite(int pin, int time) {
for(int i = 0; i <= time\/26; i++) {
digitalWrite(pin, HIGH);
delayMicroseconds(13);
digitalWrite(pin, LOW);
delayMicroseconds(13);
}
}
<\/code>
This was to be the key to making it all work. I have no way of knowing if the actual modulation of the Pro-Lite IR remote is 38KHz but it seemed to work.<\/p>\n

The next step was to pack the pulse widths into the five known types to put it into code. Perl to the rescue again.

A: S001011110110SRS001011110110SRS00100000
B: S001010001011SRS001010001011SRS00101000
C: S001010100011SRS001010100011SRS00100000
..
M: S001001000010SRS001001000010SRS00100100
..
X: S001011101011SRS001011101011SRS00101110
Y: S001010001110SRS001010001110SRS00101000
Z: S001011111010SRS001011111010SRS00101111
<\/code>
You'll notice I said five types yet there are only four represented above. That's because the five pulse (which I've called null) is between every pulse (the dip down to 0 on the graph). You'll also notice that the bitstreams always begin with “S0010” which I've hard coded since every pulse begins with it. You'll also notice the bitstream repeats a few times. So, when you reduce and remove repeats, you're left with this.

A: 11110110
B: 10001011
C: 10100011
..
<\/code>
Which reduces further into decimal, saving valuable memory space on the Arduino.

int A = 246;
int B = 139;
int C = 163;
int D = 170;
int E = 166;
int F = 202;
int G = 135;
int H = 10;
int I = 78;
..
<\/code>
Next up, finish up the code and give it a test drive.<\/p>\n","protected":false},"excerpt":{"rendered":"

To make the Arduino transmit IR signals, you need an IR LED. I found a couple from an old Sun optical mouse and an old TV remote control. I used two emitters because that's what the original Pro-Lite remote has inside and it also gains distance (I hoped). I should probably be connecting these LEDs […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3,8],"tags":[],"_links":{"self":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts\/392"}],"collection":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=392"}],"version-history":[{"count":0,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts\/392\/revisions"}],"wp:attachment":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=392"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=392"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=392"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}