use a led matrix 5x7 without driver chip?

a next step...

Pulled some TBC20-12/... from junk - bi-color green/red and orange 5x7 LED modules... and I did - for testing them before investing more work - drive them directly with PICO... When both LEDs are on, the color is an orange. Attached you find some clips and pictures.

Below you find the code - which goes through each individual LED with given color. In console I then entered instant setInterval to indefinitely scroll through the colors while the display goes through all LEDs, one by one.

// TBC20-12-test5.js
// 5x7 red, green and orange dot display w/ common cathode (bi-color)
// http://www.kingbrightusa.com/images/cata­log/SPEC/TBC20-12EGWA.pdf
// cycle to all dots in selected color
//
// NOTE: use auto pinMode!
//
// --- Wiring:
// Row R1..R7 Anodes - common, for all AND green and red rows
// Col gC1..gC5 and rC1..rC5 green and rED Cathodes - ten (10)
// GPIOs Espruibo PICO A# and B#
//
//   4    5    6    7    8    9   10   11   12  (13)
//  B3   B4   B5   B6   B7   A8   B8   B9  A10  (A0)
//   |    |    |    |    |    |    |    |    |  - direct connetion
//  18   17   16   15   14   13   12   11   10    watch alignment
// rC1   R3   R1   R2   R4  gC3  gC4  rC5  gC5
//
//
// gC1  gC2  rC2  rC3   R6   R7  rC4   R5  NC?
//   1    2    3    4    5    6    7    8    9   watch alignment
//   :    :    :    :    :    :    :    :    : - wired from 'above'
// B13  B10   B1   A7   A6   A5   A4   A3   A2  (A1)
//  23   22   21   20   19   18   17   16   15  (1$)

// --- Row / Col pin assignments (according to wiring, see picture)
//
//        R1  R2  R3  R4  R5  R6  R7
var rps=[ B5, B6, B4, B7, A3, A6, A5]; // row pins - R1..R7
//
//       rC1 rC2 rC3 rC4 rC5 gC1 gC2 gC3 gC4 gC5
var cps=[ B3, B1, A7, A4, B9,B13,B10, A8, B8,A10]; // col pins (r, g)

// --- Hauskeeping
var rMax=6; // Row maximum 0..6
var cMax=4; // Col maximum 0..4
var rpOn, cpOn; // previus row/col pin(s) on for switching off in next cycle
var r=rMax, c=cMax; // row/col last - but not on - to start with first

// --- Rum parameters - speed and color
// can be change in console while running
var t0=100;  // default and previous cycle time (see below)
var t=t0;    // cycle time (>0) - cycle invokes itself after t [ms]
var color=1; // Color 1=red, 2=green, 3=orange (red and green at same time)

// core function: cycle:
// - switch old of, increment and switch new on - col as well as row
// - row concitional on column start over
function cycle() {
  if (cpOn) digitalRead(cpOn); // 'switch' off (by making it/them input) 
  if (++c>cMax) { // start over w/ col 0
    c=0;
    if (rpOn) digitalRead(rpOn); // 'switch off' (by making it/them input) 
    if (++r>rMax) { // start over w/ row 0
      r=0;
    }
    rpOn=rps[r]; // row pin
    digitalWrite(rpOn,1); // pull anode up
  }
  cpOn // col pin(s)                 // select col pin(s) for color case:
    = (color==3) ? [cps[c],cps[c+5]] // both red and green creating orange
    : (color==2) ? cps[c+5]          // green
    : cps[c]                         // red (default)
    ;
  digitalWrite(cpOn,0); // pull cathode(s) down
  if (t>0) {
    setTimeout(cycle,t);
  } else {
    if (cpOn) digitalRead(cpOn); // 'switch' off (by making it/them input) 
    if (rpOn) digitalRead(rpOn); // 'switch off' (by making it/them input) 
  }
}

function h() { // halt
  t0=t;
  t=0;
}
function resume() { // resume / run
  t=t0;
  cycle();
}
function onInit() {
  cycle(); // auto start cycle onInit
}

setTimeout(onInit,500); // auto onInit while developing

The first shot is taken with flash: you can barely see green in 6th row and 1st column on. I could increase the supply (Anode) voltage to 5 Volt, for example, but that would already require some driver... even if it is just a buffer... or level shifter. Second shot is taken with normal light and color can be seen better... of course, it is also red, which is easy to detect. Last shot is interesting: because taken in low light, the shutter picked up an outgoing and an incoming LED... ;O

Putting multiples of these 5x7 LED modules into a panel requires lots of losts of lots of wiring... therefore, the post about running text out of an Espruino Graphics buffer will come a bit later.

5 Attachments

• m5x7gro_normalLight.mp4
• m7x5gro_lowLight.mp4
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