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Merged
urish merged 2 commits into from
Jan 22, 2022
Merged

Minor fixes to charlieplexing example code #22

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21d9582
Fix last example so all pins are set to INPUTS at the end of the loop!
arduino12 Jan 22, 2022
6fdf92c
Replaced all for-loop iterators types to byte, and rename LED to LED_PIN
arduino12 Jan 22, 2022
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136 changes: 68 additions & 68 deletions pages/guides/charlieplexing.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -289,9 +289,9 @@ for us to extend later:
#define SCAN_DELAY 500

/* gac: The port pins are defined as an array. In this case it will be two port pins: 2, 3 */
byte LEDS[] = { 2, 3 };
/* gac: to derive the number of port pins. LED_COUNT will get a value of 2 */
const byte LED_COUNT = sizeof(LEDS);
byte LED_PINS[] = { 2, 3 };
/* gac: to derive the number of port pins. LED_PIN_COUNT will get a value of 2 */
const byte LED_PIN_COUNT = sizeof(LED_PINS);

void setup() {
}
Expand All @@ -300,32 +300,32 @@ void loop() {
/* gac:
Variables `i` and `j` represent port pins of the Arduino.
In first iteration, <br />
`i` will have value of 0 --> LEDS[i] will be 2 (first element in the array) <br />
`j` will have value of 0 --> LEDS[j] will be 2.
`i` will have value of 0 --> LED_PINS[i] will be 2 (first element in the array) <br />
`j` will have value of 0 --> LED_PINS[j] will be 2.

`if` condition will fail.

In the second iteration of inner for-loop, LEDS[j] will be 3.
In the second iteration of inner for-loop, LED_PINS[j] will be 3.
The `if` condition will pass.

Since there are only two port pins, go through the iterations manually to see the logic by yourself.
you can leave a comment if there is need for more clarity
*/
for (int i = 0; i < LED_COUNT; i++) {
for (int j = 0; j < LED_COUNT; j++) {
for (byte i = 0; i < LED_PIN_COUNT; i++) {
for (byte j = 0; j < LED_PIN_COUNT; j++) {
if (i != j) { //The LED port pins are always connected to two different pins
pinMode(LEDS[i], OUTPUT); //port 2
pinMode(LEDS[j], OUTPUT); //port 3
pinMode(LED_PINS[i], OUTPUT); //port 2
pinMode(LED_PINS[j], OUTPUT); //port 3
/* gac: writing port pins with the below sequence, will turn on LED(i,j)
In first iteration, the LED(2,3) will be turned on.
In the second iteration, LED(3,2) will be turned on.
*/
digitalWrite(LEDS[i], LOW);
digitalWrite(LEDS[j], HIGH);
digitalWrite(LED_PINS[i], LOW);
digitalWrite(LED_PINS[j], HIGH);
delay(SCAN_DELAY);
/* gac: We will always take the pins to high impedance state before driving the next pins */
pinMode(LEDS[i], INPUT);
pinMode(LEDS[j], INPUT);
pinMode(LED_PINS[i], INPUT);
pinMode(LED_PINS[j], INPUT);
}
}
}
Expand Down Expand Up @@ -361,24 +361,24 @@ And the 6 LEDs arranged as follows:

#define SCAN_DELAY 500

/* gac: Life is simple now - we can support as many pins as we want by adding values to the `LEDS` array */
byte LEDS[] = { 2, 3, 4 };
const byte LED_COUNT = sizeof(LEDS);
/* gac: Life is simple now - we can support as many pins as we want by adding values to the `LED_PINS` array */
byte LED_PINS[] = { 2, 3, 4 };
const byte LED_PIN_COUNT = sizeof(LED_PINS);

void setup() {
}

void loop() {
for (int i = 0; i < LED_COUNT; i++) {
for (int j = 0; j < LED_COUNT; j++) {
for (byte i = 0; i < LED_PIN_COUNT; i++) {
for (byte j = 0; j < LED_PIN_COUNT; j++) {
if (i != j) {
pinMode(LEDS[i], OUTPUT);
pinMode(LEDS[j], OUTPUT);
digitalWrite(LEDS[i], LOW);
digitalWrite(LEDS[j], HIGH);
pinMode(LED_PINS[i], OUTPUT);
pinMode(LED_PINS[j], OUTPUT);
digitalWrite(LED_PINS[i], LOW);
digitalWrite(LED_PINS[j], HIGH);
delay(SCAN_DELAY);
pinMode(LEDS[i], INPUT);
pinMode(LEDS[j], INPUT);
pinMode(LED_PINS[i], INPUT);
pinMode(LED_PINS[j], INPUT);
}
}
}
Expand All @@ -398,7 +398,7 @@ void loop() {
#### Code Summary

Since we made our code modular, we only had to change a single place: add the
new pin number (4) to the `LEDS[]` array.
new pin number (4) to the `LED_PINS[]` array.

### Case 3: Driving twelve LEDs with four Arduino Pins-Charlieplexing

Expand Down Expand Up @@ -431,23 +431,23 @@ You have 12 LEDs in this case

#define SCAN_DELAY 500

byte LEDS[] = { 2, 3, 4, 5 };
const byte LED_COUNT = sizeof(LEDS);
byte LED_PINS[] = { 2, 3, 4, 5 };
const byte LED_PIN_COUNT = sizeof(LED_PINS);

void setup() {
}

void loop() {
for (int i = 0; i < LED_COUNT; i++) {
for (int j = 0; j < LED_COUNT; j++) {
for (byte i = 0; i < LED_PIN_COUNT; i++) {
for (byte j = 0; j < LED_PIN_COUNT; j++) {
if (i != j) {
pinMode(LEDS[i], OUTPUT);
pinMode(LEDS[j], OUTPUT);
digitalWrite(LEDS[i], LOW);
digitalWrite(LEDS[j], HIGH);
pinMode(LED_PINS[i], OUTPUT);
pinMode(LED_PINS[j], OUTPUT);
digitalWrite(LED_PINS[i], LOW);
digitalWrite(LED_PINS[j], HIGH);
delay(SCAN_DELAY);
pinMode(LEDS[i], INPUT);
pinMode(LEDS[j], INPUT);
pinMode(LED_PINS[i], INPUT);
pinMode(LED_PINS[j], INPUT);
}
}
}
Expand Down Expand Up @@ -494,23 +494,23 @@ You have 20 LEDs in this case:

#define SCAN_DELAY 500

byte LEDS[] = { 2, 3, 4, 5, 6 };
const byte LED_COUNT = sizeof(LEDS);
byte LED_PINS[] = { 2, 3, 4, 5, 6 };
const byte LED_PIN_COUNT = sizeof(LED_PINS);

void setup() {
}

void loop() {
for (int i = 0; i < LED_COUNT; i++) {
for (int j = 0; j < LED_COUNT; j++) {
for (byte i = 0; i < LED_PIN_COUNT; i++) {
for (byte j = 0; j < LED_PIN_COUNT; j++) {
if (i != j) {
pinMode(LEDS[i], OUTPUT);
pinMode(LEDS[j], OUTPUT);
digitalWrite(LEDS[i], LOW);
digitalWrite(LEDS[j], HIGH);
pinMode(LED_PINS[i], OUTPUT);
pinMode(LED_PINS[j], OUTPUT);
digitalWrite(LED_PINS[i], LOW);
digitalWrite(LED_PINS[j], HIGH);
delay(SCAN_DELAY);
pinMode(LEDS[i], INPUT);
pinMode(LEDS[j], INPUT);
pinMode(LED_PINS[i], INPUT);
pinMode(LED_PINS[j], INPUT);
}
}
}
Expand Down Expand Up @@ -549,7 +549,7 @@ And the LEDs:
</figure>

The code was omitted for brevity. We basically add the number `7` at the end of the
`LEDS` array.
`LED_PINS` array.

### Case 6: Driving 42 LEDs with 7 Arduino Pins-Charlieplexing

Expand Down Expand Up @@ -629,23 +629,23 @@ So what's the trick?
LEDs are all lit at once. Even though we still light them just one at a time! */
#define SCAN_DELAY 1

byte LEDS[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10 };
const byte LED_COUNT = sizeof(LEDS);
byte LED_PINS[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10 };
const byte LED_PIN_COUNT = sizeof(LED_PINS);

void setup() {
}

void loop() {
for (int i = 0; i < LED_COUNT; i++) {
for (int j = 0; j < LED_COUNT; j++) {
for (byte i = 0; i < LED_PIN_COUNT; i++) {
for (byte j = 0; j < LED_PIN_COUNT; j++) {
if (i != j) {
pinMode(LEDS[i], OUTPUT);
pinMode(LEDS[j], OUTPUT);
digitalWrite(LEDS[i], LOW);
digitalWrite(LEDS[j], HIGH);
pinMode(LED_PINS[i], OUTPUT);
pinMode(LED_PINS[j], OUTPUT);
digitalWrite(LED_PINS[i], LOW);
digitalWrite(LED_PINS[j], HIGH);
delay(SCAN_DELAY);
pinMode(LEDS[i], INPUT);
pinMode(LEDS[j], INPUT);
pinMode(LED_PINS[i], INPUT);
pinMode(LED_PINS[j], INPUT);
}
}
}
Expand All @@ -665,17 +665,17 @@ of one LED at the time. This way, each LED will get power for ~1/9 of the time:

#define SCAN_DELAY 1

byte LEDS[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10 };
const byte LED_COUNT = sizeof(LEDS);
byte LED_PINS[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10 };
const byte LED_PIN_COUNT = sizeof(LED_PINS);

void setup() {
}

void loop() {
for (int i = 0; i < LED_COUNT; i++) {
pinMode(LEDS[i], OUTPUT);
digitalWrite(LEDS[i], LOW);
for (int j = 0; j < LED_COUNT; j++) {
for (byte i = 0; i < LED_PIN_COUNT; i++) {
pinMode(LED_PINS[i], OUTPUT);
digitalWrite(LED_PINS[i], LOW);
for (byte j = 0; j < LED_PIN_COUNT; j++) {
if (i != j) {
/* gac:start
if you wanted just some specific LEDs to be on, we'd need to add another condition
Expand All @@ -685,15 +685,15 @@ void loop() {
the pin is set both to `OUTPUT` and `LOW`. Otherwise, some current may flow from
other `HIGH` pins to this pin, briefly lighting up LEDs we didn't want to.
*/
digitalWrite(LEDS[j], HIGH);
pinMode(LEDS[j], OUTPUT);
digitalWrite(LED_PINS[j], HIGH);
pinMode(LED_PINS[j], OUTPUT);
/* gac:end */
}
}
delay(SCAN_DELAY);
for (int j = 0; j < LED_COUNT; j++) {
digitalWrite(LEDS[i], LOW);
pinMode(LEDS[j], INPUT);
for (byte j = 0; j < LED_PIN_COUNT; j++) {
digitalWrite(LED_PINS[j], LOW);
pinMode(LED_PINS[j], INPUT);
}
}
}
Expand Down