Charlie-plexing

**Demon** · - 18th December 2014, 06:04

This:

Code:

' Blink 56 LEDs connected to PORT A in charlie-plex manner

'   PIC             18F44K22    int osc 64MHz
'   PBP             v2.60c
'   MPASM           v5.49
'   MCS+            v2.1.0.7
'   U2 programmer   v4.32

asm
 __CONFIG    _CONFIG1H, _FOSC_INTIO67_1H & _PLLCFG_ON_1H & _PRICLKEN_OFF_1H & _FCMEN_ON_1H & _IESO_OFF_1H
 __CONFIG    _CONFIG2L, _PWRTEN_ON_2L & _BOREN_SBORDIS_2L & _BORV_285_2L
 __CONFIG    _CONFIG2H, _WDTEN_OFF_2H
 __CONFIG    _CONFIG3H, _CCP2MX_PORTC1_3H & _PBADEN_OFF_3H & _CCP3MX_PORTE0_3H & _HFOFST_OFF_3H & _T3CMX_PORTB5_3H & _P2BMX_PORTC0_3H & _MCLRE_EXTMCLR_3H
 __CONFIG    _CONFIG4L, _STVREN_OFF_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L
endasm

DEFINE OSC 64

OSCCON  = %01110000              ' OSCILLATOR CONTROL REGISTER
' bit 7 IDLEN: Idle Enable bit
'     R/W       1 = Device enters Idle mode on SLEEP instruction
'               0 = Device enters Sleep mode on SLEEP instruction
' bit 6-4 IRCF<2:0>: Internal RC Oscillator Frequency Select bits(2)
'     R/W       111 = HFINTOSC – (16 MHz)
'               110 = HFINTOSC/2 – (8 MHz)
'               101 = HFINTOSC/4 – (4 MHz)
'               100 = HFINTOSC/8 – (2 MHz)
'               011 = HFINTOSC/16 – (1 MHz)(3)
'           If INTSRC = 0 and MFIOSEL = 0:
'               010 = HFINTOSC/32 – (500 kHz)
'               001 = HFINTOSC/64 – (250 kHz)
'               000 = LFINTOSC – (31.25 kHz)
'           If INTSRC = 1 and MFIOSEL = 0:
'               010 = HFINTOSC/32 – (500 kHz)
'               001 = HFINTOSC/64 – (250 kHz)
'               000 = HFINTOSC/512 – (31.25 kHz)
'           If INTSRC = 0 and MFIOSEL = 1:
'               010 = MFINTOSC – (500 kHz)
'               001 = MFINTOSC/2 – (250 kHz)
'               000 = LFINTOSC – (31.25 kHz)
'           If INTSRC = 1 and MFIOSEL = 1:
'               010 = MFINTOSC – (500 kHz)
'               001 = MFINTOSC/2 – (250 kHz)
'               000 = MFINTOSC/16 – (31.25 kHz)
' bit 3 OSTS: Oscillator Start-up Time-out Status bit
'       R       1 = Device is running from the clock defined by FOSC<3:0> of the CONFIG1H register
'               0 = Device is running from the internal oscillator (HFINTOSC, MFINTOSC or LFINTOSC)
' bit 2 HFIOFS: HFINTOSC Frequency Stable bit
'       R       1 = HFINTOSC frequency is stable
'               0 = HFINTOSC frequency is not stable
' bit 1-0 SCS<1:0>: System Clock Select bit
'       R/W     1x = Internal oscillator block
'               01 = Secondary (SOSC) oscillator
'               00 = Primary clock (determined by FOSC<3:0> in CONFIG1H).

OSCCON2 = %00000100              ' OSCILLATOR CONTROL REGISTER 2
' bit 7 PLLRDY: PLL Run Status bit
'     R         1 = System clock comes from 4xPLL
'               0 = System clock comes from an oscillator, other than 4xPLL
' bit 6 SOSCRUN: SOSC Run Status bit
'     R         1 = System clock comes from secondary SOSC
'               0 = System clock comes from an oscillator, other than SOSC
' bit 5 Unimplemented: Read as ‘0’.
' bit 4 MFIOSEL: MFINTOSC Select bit
'     R/W=0     1 = MFINTOSC is used in place of HFINTOSC frequencies of 500 kHz, 250 kHz and 31.25 kHz
'               0 = MFINTOSC is not used
' bit 3 SOSCGO(1): Secondary Oscillator Start Control bit
'     R/W=0     1 = Secondary oscillator is enabled.
'               0 = Secondary oscillator is shut off if no other sources are requesting it.
' bit 2 PRISD: Primary Oscillator Drive Circuit Shutdown bit
'     R/W=1     1 = Oscillator drive circuit on
'               0 = Oscillator drive circuit off (zero power)
' bit 1 MFIOFS: MFINTOSC Frequency Stable bit
'     R         1 = MFINTOSC is stable
'               0 = MFINTOSC is not stable
' bit 0 LFIOFS: LFINTOSC Frequency Stable bit
'     R         1 = LFINTOSC is stable
'               0 = LFINTOSC is not stable

OSCTUNE = %11000000              ' OSCILLATOR TUNING REGISTER
' bit 7 INTSRC: Internal Oscillator Low-Frequency Source Select bit
'     R/W       1 = 31.25 kHz device clock derived from the MFINTOSC or HFINTOSC source
'               0 = 31.25 kHz device clock derived directly from LFINTOSC internal oscillator
' bit 6 PLLEN: Frequency Multiplier 4xPLL for HFINTOSC Enable bit(1)
'     R/W       1 = PLL enabled
'               0 = PLL disabled
' bit 5-0 TUN<5:0>: Frequency Tuning bits – use to adjust MFINTOSC and HFINTOSC frequencies
'     R/W       011111 = Maximum frequency
'               011110 =
'               • • •
'               000001 =
'               000000 = Oscillator module (HFINTOSC and MFINTOSC) are running at the factory calibrated frequency.
'               111111 =
'               • • •
'               100000 = Minimum frequency

ANSELA = %00000000          ' Set ports to digital
ANSELB = %00000000
ANSELC = %00000000
ANSELD = %00000000
ANSELE = %00000000

ADCON0 = %00000000          ' Disable ADC

TRISA = %00000000           ' Set all Ports to output 
TRISB = %00000000
TRISC = %00000000
TRISD = %00000000
TRISE = %00000000
PORTA = %00000000           ' Set ports OFF
PORTB = %00000000
PORTC = %00000000
PORTD = %00000000
PORTE = %00000000

varLEDstate VAR BYTE[55]
varLEDport  VAR BYTE[55]
varArray    var byte
varEEPROM   var byte

varEEPROM = 0

'-------------------------   T E M P O R A R Y   ------------------------------
for varArray = 0 to 55                      ' Location in Array
    varEEPROM = varEEPROM + 1               ' Location in EEPROM
    read varEEPROM, VARLEDstate[varArray]
    varEEPROM = varEEPROM + 1
    read varEEPROM, VARLEDport[varArray]
next varArray
'------------------------------------------------------------------------------

    pause 100

mainloop:

    for varArray = 0 to 55               ' LEDs in ascending sequence
        TRISA = VARLEDSTATE[varArray]
        PORTA = VARLEDPORT[varArray]
        PAUSE 15
    next varArray

    for varArray = 55 to 0 step -1      ' LEDs in decending sequence
        TRISA = VARLEDSTATE[varArray]
        PORTA = VARLEDPORT[varArray]
        PAUSE 15
    next varArray
 
    goto mainloop
End


DATA @1,%11111100   ' Pin A0
DATA %00000001

DATA %11111010
DATA %00000001

DATA %11110110
DATA %00000001

DATA %11101110
DATA %00000001

DATA %11011110
DATA %00000001

DATA %10111110
DATA %00000001

DATA %01111110
DATA %00000001

DATA %11111100   ' Pin A1
DATA %00000010

DATA %11111001
DATA %00000010

DATA %11110101
DATA %00000010

DATA %11101101
DATA %00000010

DATA %11011101
DATA %00000010

DATA %10111101
DATA %00000010

DATA %01111101
DATA %00000010

DATA %11111010   ' Pin A2
DATA %00000100

DATA %11111001
DATA %00000100

DATA %11110011
DATA %00000100

DATA %11101011
DATA %00000100

DATA %11011011
DATA %00000100

DATA %10111011
DATA %00000100

DATA %01111011
DATA %00000100

DATA %11110110   ' Pin A3
DATA %00001000

DATA %11110101
DATA %00001000

DATA %11110011
DATA %00001000

DATA %11100111
DATA %00001000

DATA %11010111
DATA %00001000

DATA %10110111
DATA %00001000

DATA %01110111
DATA %00001000

DATA %11101110   ' Pin A4
DATA %00010000

DATA %11101101
DATA %00010000

DATA %11101011
DATA %00010000

DATA %11100111
DATA %00010000

DATA %11001111
DATA %00010000

DATA %10101111
DATA %00010000

DATA %01101111
DATA %00010000

DATA %11011110   ' Pin A5
DATA %00100000

DATA %11011101
DATA %00100000

DATA %11011011
DATA %00100000

DATA %11010111
DATA %00100000

DATA %11001111
DATA %00100000

DATA %10011111
DATA %00100000

DATA %01011111
DATA %00100000

DATA %10111110   ' Pin A6
DATA %01000000

DATA %10111101
DATA %01000000

DATA %10111011
DATA %01000000

DATA %10110111
DATA %01000000

DATA %10101111
DATA %01000000

DATA %10011111
DATA %01000000

DATA %00111111
DATA %01000000

DATA %01111110   ' Pin A7
DATA %10000000

DATA %01111101
DATA %10000000

DATA %01111011
DATA %10000000

DATA %01110111
DATA %10000000

DATA %01101111
DATA %10000000

DATA %01011111
DATA %10000000

DATA %00111111
DATA %10000000

Scanning through 56 LEDs:

Persistence of vision, no noticeable difference (not all LEDs point directly up):

Current consumption (removed Power Indicator LED from circuit):
- all off = 11.5mA
- all on = 22.0 mA

Robert

**Demon** · - 21st December 2014, 01:00

Only one LED will be bright enough to be visible even though multiple paths are active at the same time, because the shortest path is the only one with enough current. All the other undesired paths share the same current; not enough to make an LED glow.

Cycling through the 56 LEDs on the 8 pins in the post above, a LED does not have enough current 7 out of 8 times:

From Step 4:

...
OK, so a current flows through LED5, current isn't flowing through LED6 because it is reverse biased (and so are LED2 and LED4)....but there is also a path for the current to take from pin A, through LED1 and LED3 isn't there? Why are these LEDs not glowing as well.

Here is the heart of the charlieplexing scheme. Indeed there is a current flowing both LED1 and LED3, however the voltage across the both of these combined is only going to be equal to the voltage across LED5. Typically they would have half the voltage across them that LED5 has. So if we have 1.9V across LED5, then only 0.95V will be across LED1 and 0.95V across LED3.

From the If/Vf curve mentioned at the beginning of this article we can see that the current at this half voltage is much much lower than 20mA.....and those LEDs will not glow visibly. This is known as current stealing.

Thus most of the current will flow though the LED we want, the most direct path through the least number of LEDs (ie one LED), rather than any series combination of LEDs.
...

http://www.instructables.com/id/Char...eory/?ALLSTEPS

Robert

(That Habs logo just "happened" to line up with the monitor.)