Charlie Plexing
Charliplexing ist eine möglichkeit durch geschickte Verwendung der drei Zustände $Low$, $High$ und $Z$ (= Tri-state) aus durch wenige Pins viele LEDs anzusteuern. Dabei wir ausgenutzt, dass in den hochohmigen Pin, welcher auf $Z$ „liegt“, kein Strom fließen kann und dieser auch keinen Spannungswert definiert.
Beispiel eines Charlieplexing
In Abbildung 1 ist ein Beispiel für Charlieplexing dargestellt. es ist folgendes zu sehen:
- Links ist die gewünschte Outputmatrix zu sehen, in welchem durch Druck auf $H$ bzw. $L$ die gewünschte LED aktiviert bzw. deaktiviert werden kann.
- In der Mitte ist die Logik zu sehen, auf die im gleich nochmals eingegangen wird.
- Rechts ist die LED Matrix zu finden, welche durch Charlieplexing angesteuert wird.
Es soll nun die Logik etwas näher beschrieben werden. Dies kann auch durch Reduktion der Simulationsgeschwindigkeit besser in der Simulation sichtbar gemacht werden:
- Es ist ersichtlich, dass jeweils für ein nebeneinander liegendes LED-Pärchen im Charlieplexing Anode und Kathode vertauscht sind.
Im Code werden deshalb immer zwei nebeneinander liegende Werte in der Outputmatrix gleichzeitig behandelt. (Siehe Zeile 141ff inCharlieP.c) Dabei ist für die LED links oben ([0][0]) die Kathode gerade der Pin des Ports $PORTx.0$. - UM eine LED leuchten zu lassen wird ein bestimmter Pin eines Ports auf $High$ gesetzt, z.B. $PORTx.0$. Für diesen Pin muss auch das Datenrichtungsregister auf $High$ gesetzt werden, dies geschieht durch das $ODER$-Gatter vor dem $DDRx.0$ Pin.
Im Code wird dafür im Zeile 158 und 159 dieportMatrixgefüllt. - Für die LEDs in der ersten Reihe ist $PORTx.0$ entweder die Kathode (jede zweite LED ab [0][0]) oder Anode (jede zweite LED ab [0][1]).
Gleiches gilt für die zweite Reihe für $PORTx.1$. Für die dritte Reihe gilt dies nur für die ersten beiden LEDs.
Im Code schlägt sich dies in der Ermittlung deractCathodefür ein LED-Pärchen in Zeile 145 bzw. 148 nieder.
Lib
Wichtig:
- Die vorliegende Lib (und damit der Code unten) ist nur für eine gerade Anzahl von Pins geeignet.
- Zudem muss die Anordnung des Charlieplexings wie im folgenden Bild dargestellt eingehalten werden.
Code
CharlieP.h
/*
* CharlieP.h
*
* Created: 10.12.2022 22:30:57
* Author: Tim Fischer
*/
#ifndef CHARLIEP_H_
#define CHARLIEP_H_
//Makros for bit manipulation
#define SET_BIT(BYTE, BIT) ((BYTE) |= (1<<BIT)) // set single BIT in BYTE
#define CLR_BIT(BYTE, BIT) ((BYTE) &= ~(1<<BIT)) // clear single BIT in BYTE
#define CHG_BIT(BYTE, BIT, VAL) ((BYTE) = ((BYTE) & ~(1<<BIT)) | (VAL<<BIT)) // change single BIT in BYTE to VAL
#define TGL_BIT(BYTE, BIT) ((BYTE) ^= (1 << (BIT))) // toggle single BIT in BYTE
#define PIN_COUNT 12 // overall number of pins used
#define PORT_COUNT 3 // number of ports used
enum PORTS {PORT_B, PORT_C, PORT_D, DDR_B, DDR_C, DDR_D}; // in this example three different Ports are used for output. This can also be change to more or less
enum P { PB, PC, PD}; // In this case, the matrizes outputPort, outputPin and portMatrix have to be adapted
#define DONE 1 // return value for finished round over all anodes
//function prototypes
extern uint8_t CharlieP_setPortsForLightingLeds(void);
extern void CharlieP_setPortMatrix(void);
extern uint8_t outputMatrixXY [PIN_COUNT] [PIN_COUNT-1];
extern uint8_t portMatrix [PORT_COUNT*2] [PIN_COUNT];
#endif /* CHARLIEP-H_H_ */
CharlieP.c
/*
* CharlieP.c
*
* Created: 10.12.2022 22:30:48
* Author: Tim Fischer
*
* The following code drives charlieplexed LED arrays. For this, the array shall have the following structure:
*
* colNr-> 0 1 2 3
*
* rowNr PIN0 ----------------------------
* v | | | |
* | | ^ v . . . . . . . . . . . . This is LED[0,3]
* 0 ^ v | |
* | | ------PIN2
* | |
* PIN1 ----------------------------
* | | | |
* | | ^ v
* 1 ^ v | |
* | | ------PIN3
* | |
* PIN2 ----------------------------
* | |
* | | ------PIN0
* 2 ^ v | |
* | | ^ v
* | | | |
* PIN3 -----------------------------
*
* This example is explained more:
* - The numbers of pins is PIN_COUNT = 4.
* - There are groups of independent LEDs. There are as much groups of independent LEDs as numbers of pins.
* - Example for independent LEDs:
* - assume only PIN0 is HIGH and all other pins are at high-impedance.
* - Then the anode on some LEDs is at 5V.
* - For LED[0,1], LED[0,3] and LED[2,3] anode is HIGH. These can independently be activated, by switching their cathode to LOW.
* - The active output anode has to be stepped through all PIN_COUNT pins.
* - The arrangements of the ANODES can be read from the circuit above:
* rowNr, colNr-> 0 1 2 3
* 0 PIN1 PIN0 PIN2 PIN0
* 1 PIN2 PIN1 PIN3 PIN1
* 2 PIN3 PIN2 PIN3 PIN0
*
* - The arrangements of the CATHODE is just the groups of columns rearranged (column 1 with 0, column 3 with 2)
* The ANODE becomes the CATHODE ans vice versa.
* - For PIN_COUNT = 6, the arrangements of the ANODES shall be as follows:
* rowNr, colNr-> 0 1 2 3 4 5
* 0 PIN1 PIN0 PIN2 PIN0 PIN3 PIN0
* 1 PIN2 PIN1 PIN3 PIN1 PIN4 PIN1
* 2 PIN3 PIN2 PIN4 PIN2 PIN5 PIN2
* 3 PIN4 PIN3 PIN5 PIN3 PIN4 PIN0
* 4 PIN5 PIN4 PIN5 PIN0 PIN5 PIN1
*
* - For PIN_COUNT = 8, the arrangements of the ANODES shall be as follows:
* rowNr, colNr-> 0 1 2 3 4 5 6 7
* 0 PIN1 PIN0 PIN2 PIN0 PIN3 PIN0 PIN4 PIN0
* 1 PIN2 PIN1 PIN3 PIN1 PIN4 PIN1 PIN5 PIN1
* 2 PIN3 PIN2 PIN4 PIN2 PIN5 PIN2 PIN6 PIN2
* 3 PIN4 PIN3 PIN5 PIN3 PIN6 PIN3 PIN7 PIN3
* 4 PIN5 PIN4 PIN6 PIN4 PIN7 PIN4 PIN5 PIN9
* 5 PIN6 PIN5 PIN7 PIN5 PIN6 PIN0 PIN6 PIN1
* 6 PIN7 PIN6 PIN7 PIN0 PIN7 PIN1 PIN7 PIN2
* - The systematic is as following:
* - every EVEN column (for UPward pointing LED) is a progression of rowNr + colNr + 1 until it reaches PIN_COUNT-1.
* After this, the numbers reflect the rowNr+1
* - every ODD column (for DOWNward pointing LED) is a progression of rowNr until rowNr + colNr + 1 reaches PIN_COUNT-1.
* After this, it is counting up again from 0 (= actAnode - PIN_COUNT).
*
*/
#include <avr/io.h> // lib for I/O config
#include <stdbool.h> // lib for Bit variables
#include <avr/interrupt.h> // lib for standard interrupts
#include "charlieP.h" // lib for charlie plexing
uint8_t outputPort[PIN_COUNT]={ DDR_C, DDR_C, DDR_D, DDR_D, DDR_D, DDR_D, DDR_D, DDR_D, DDR_D, DDR_D, DDR_B, DDR_B}; // This array shows the PORTs used for driving the charlieplexed LEDs
uint8_t outputPin [PIN_COUNT]={ PC2, PC3, PD0, PD1, PD2, PD3, PD4, PD5, PD6, PD7, PB0, PB1}; // This array shows the PINs used for driving the charlieplexed LEDs
uint8_t outputMatrixXY[PIN_COUNT][PIN_COUNT-1]={}; // this array reflects the LEDs which have to be activated
// The dimensions are the same as in the geometry: [column][row]
uint8_t portMatrix [PORT_COUNT*2][PIN_COUNT]={
//Definition of Port Nr 0 1 2 3 4 5 6 7 8 9 10 11 // the portMatrix is used to set the wanted ports to output HIGH or low
// // When, no output is wanted only the anodes are set to output HIGH
// // and the cathodes are set to high impedance (bit in DDRx = 0)
/*PORT_B*/ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1<<PB0, 1<<PB1}, //PORT_B
/*PORT_C*/ { 1<<PC2, 1<<PC3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, //PORT_C
/*PORT_D*/ { 0, 0, 1<<PD0, 1<<PD1, 1<<PD2, 1<<PD3, 1<<PD4, 1<<PD5, 1<<PD6, 1<<PD7, 0, 0}, //PORT_D
/* DDR_B*/ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1<<PB0, 1<<PB1}, // DDR_B
/* DDR_C*/ { 1<<PC2, 1<<PC3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // DDR_C
/* DDR_D*/ { 0, 0, 1<<PD0, 1<<PD1, 1<<PD2, 1<<PD3, 1<<PD4, 1<<PD5, 1<<PD6, 1<<PD7, 0, 0} // DDR_D
};
/*********************************************************************
*
* CharlieP_setPortsForLightingLeds
*
* - IMPORTANT: this function has to be in a cycle of about 10ms in order to have a tradeoff between dynamic changes of the output but long persistence for visibility
* - Sets the ports for one anode (= one pin) active
* - multiple independent LEDs can be activated
* - function outputs DONE, when all anodes were set to active. otherwise it outputs 0.
*
*********************************************************************/
uint8_t CharlieP_setPortsForLightingLeds(void)
{
static uint8_t actOutputAnode = 0; // set variable as local and persistent
PORTB = portMatrix[PORT_B][actOutputAnode]; // set PORTB output values (HIGH or LOW)
PORTC = portMatrix[PORT_C][actOutputAnode]; // set PORTC output values (HIGH or LOW)
PORTD = portMatrix[PORT_D][actOutputAnode]; // set PORTD output values (HIGH or LOW)
DDRB = portMatrix[DDR_B ][actOutputAnode]; // set DDRB output values (high-omhic or PORTB value)
DDRC = portMatrix[DDR_C ][actOutputAnode]; // set DDRC output values (high-omhic or PORTD value)
DDRD = portMatrix[DDR_D ][actOutputAnode]; // set DDRD output values (high-omhic or PORTC value)
actOutputAnode++; // next anode
if (actOutputAnode < PIN_COUNT) return 0; // when not the last anode -> exit with returning 0
actOutputAnode = 0; // when the last anode -> set back to first
return DONE; // when the last anode -> exit with returning "DONE"
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Mapping des SignalOutput Arrays ==========================================================
//mapped die Matrix auf den SignalOutout, um so die LEDs in Gruppen einzuteilen
/*********************************************************************
*
* CharlieP_setPortMatrix
*
* - maps the outputMatrixXY (xy-matrix of activatable LEDs) to the necessary port and pins
*
*********************************************************************/
void CharlieP_setPortMatrix()
{
uint8_t actCathode = 0, actPortCathode = 0, actPinCathode = 0, bitInOutputMatrixForLedUpwards = 0;
uint8_t actAnode = 0, actPortAnode = 0, actPinAnode = 0, bitInOutputMatrixForLedDownwards = 0;
for (uint8_t rowNr = 0; rowNr <PIN_COUNT-1 ; rowNr++) // loop over all rows
for (uint8_t colNr = 0; colNr <PIN_COUNT/2 ; colNr++) // loop over half the columns, since each 2nd column has antiparallel LEDs (cathode and anode switched)
{ // 'rowNr' and 'colNr' define two antiparallel LEDs
bitInOutputMatrixForLedUpwards = outputMatrixXY [colNr*2] [rowNr]; // read, whether UPward pointing LED (LED in even column) has to be activated
bitInOutputMatrixForLedDownwards = outputMatrixXY [colNr*2+1][rowNr]; // read, whether DOWNward pointing LED (LED in odd column) has to be activated
actAnode = colNr + rowNr + 1; // sets the pin of the actual anode. For details see comment in the beginning of CharlieP.c
actCathode = rowNr; // sets the pin of the actual cathode. For details see comment in the beginning of CharlieP.c
if (actAnode>= PIN_COUNT) // once the change of the charlie plexing type in the row is reached
{ //
actCathode = actAnode - PIN_COUNT; // recalculate the pin of the actual cathode. For details see comment in the beginning of CharlieP.c
actAnode = rowNr + 1; // recalculate the pin of the actual anode. For details see comment in the beginning of CharlieP.c
};
actPortCathode = outputPort[actCathode]; // get cathode PIN / PORTs for upward pointing LED, which has to be (de)activated
actPinCathode = outputPin [actCathode];
actPortAnode = outputPort[actAnode ]; // get anode PIN / PORTs for upward pointing LED, which has to be (de)activated
actPinAnode = outputPin [actAnode ];
CHG_BIT(portMatrix[actPortCathode][actAnode ], actPinCathode, bitInOutputMatrixForLedUpwards ); // change the DDR for the pin and port for the UPward pointing LED
CHG_BIT(portMatrix[actPortAnode ][actCathode], actPinAnode, bitInOutputMatrixForLedDownwards); // change the DDR for the pin and port for the DOWNward pointing LED
};
}