{"id":16205,"date":"2016-08-25T10:00:03","date_gmt":"2016-08-25T17:00:03","guid":{"rendered":"https:\/\/blog.digilentinc.com\/?p=16205"},"modified":"2021-06-16T13:56:44","modified_gmt":"2021-06-16T20:56:44","slug":"fundementals-of-writing-a-library","status":"publish","type":"post","link":"https:\/\/digilent.com\/blog\/fundementals-of-writing-a-library\/","title":{"rendered":"FUNdamentals of Writing a Library"},"content":{"rendered":"

Since working at Digilent, I have learned several lessons. One of these is that whenever I am done programming a library, I should have some fun by creating a small side project using it. This way, I can understand my library on a new depth, and find any limitations or errors in it. Also I get to have fun, which is well, always fun!<\/p>\n

\"20160816_150920\"
Having so much fun!<\/figcaption><\/figure>\n

A good example of this occurred\u00a0last week. I just finished a library for the PmodSSD<\/a>, which is a 2 digit seven segment display. This Pmod\u00a0utilizes 12 pins. Pins 1 through 7 each light up a single segment on the display, while pin 8 switches between the left and right digit. This display can only light up one digit at a time, so in order to simulate a 2 digit number it needs to flash the numbers on both sides fast enough so that the human eye can see\u00a0both numbers at once.<\/p>\n

Here is what I came up with:<\/p>\n

void SnakePattern(){
\n\/\/ start timer
\nlong startTimer = counter;
\nwhile(startTimer + displayTime > counter){
\n\/\/ select left digit
\ndigitalWrite(pinArray[7], HIGH);
\n\/\/ print snake at segment A of left digit
\ndigitalWrite(pinArray[0], HIGH);
\ndigitalWrite(pinArray[1], LOW);
\ndigitalWrite(pinArray[2], LOW);
\ndigitalWrite(pinArray[3], LOW);
\ndigitalWrite(pinArray[4], LOW);
\ndigitalWrite(pinArray[5], LOW);
\ndigitalWrite(pinArray[6], LOW);
\ndelay(1);<\/code><\/p>\n

\/\/ select right digit
\ndigitalWrite(pinArray[7], LOW);
\n\/\/ print snake at segment A of right digit
\ndigitalWrite(pinArray[0], HIGH);
\ndigitalWrite(pinArray[1], LOW);
\ndigitalWrite(pinArray[2], LOW);
\ndigitalWrite(pinArray[3], LOW);
\ndigitalWrite(pinArray[4], LOW);
\ndigitalWrite(pinArray[5], LOW);
\ndigitalWrite(pinArray[6], LOW);
\ndelay(1);
\n}
\nstartTimer = counter;
\nwhile(startTimer + displayTime > counter){
\n\/\/ select left digit
\ndigitalWrite(pinArray[7], LOW);
\n\/\/ print snake at segment B right digit
\ndigitalWrite(pinArray[0], LOW);
\ndigitalWrite(pinArray[1], HIGH);
\ndigitalWrite(pinArray[2], LOW);
\ndigitalWrite(pinArray[3], LOW);
\ndigitalWrite(pinArray[4], LOW);
\ndigitalWrite(pinArray[5], LOW);
\ndigitalWrite(pinArray[6], LOW);
\ndelay(1);<\/p>\n

\/\/ This continues on and on until pattern is done. It is a lot of lines.<\/p><\/blockquote>\n

My library was very simple, as you can see above. Basically, it takes a number, matches it to a case in a switch statement, and that case performs 7 digitalWrites() to display that number on the PmodSSD<\/a>. This function worked, and I was about to publish it.<\/p>\n

However,\u00a0I followed my lesson and decided to have some fun! Numbers are boring, I wanted to make some extravagant patterns on the display. So I set off to simulate a pattern of a snake circling around the display.<\/p>\n