speedEC
Full Member level 6
Dear friends,
MCU : PIC16F1938
LED DISPLAY (BIG SIZED): 6 DIGITS
VDD (LED DISPLAY) = +12V
LED DIGIT SIZE: 3.5" x 5"
DISPLAY: COMMON ANODE ***
POWER SUPPLY:
MAX7219 & PIC MCU = +5V
LED DISPLAY = +12V, 500mA POWER ADAPTER
I have to interface LED DISPLAY (6 Digits) from PIC MCU thru' MAX7219 IC. MAX7219 for common cathode display. I have used ULN2003 and PNP (BC557) transistors to make it work on MAX7219. I am using bitbanging (not SPI module) method (RA1 - SDO, RA2 - SS, RA3 - SCK).
Code works OK. But, if data sent to one digit, it writes on all digits. Also, when first data sent, it clears all other segments correctly and correct digit displayed on Digits. but after second data sent, it overlaps on earlier digit we have already written.
sample picture attached FYR.
what could be the problem?
thanks in advance.
MCU : PIC16F1938
LED DISPLAY (BIG SIZED): 6 DIGITS
VDD (LED DISPLAY) = +12V
LED DIGIT SIZE: 3.5" x 5"
DISPLAY: COMMON ANODE ***
POWER SUPPLY:
MAX7219 & PIC MCU = +5V
LED DISPLAY = +12V, 500mA POWER ADAPTER
I have to interface LED DISPLAY (6 Digits) from PIC MCU thru' MAX7219 IC. MAX7219 for common cathode display. I have used ULN2003 and PNP (BC557) transistors to make it work on MAX7219. I am using bitbanging (not SPI module) method (RA1 - SDO, RA2 - SS, RA3 - SCK).
Code works OK. But, if data sent to one digit, it writes on all digits. Also, when first data sent, it clears all other segments correctly and correct digit displayed on Digits. but after second data sent, it overlaps on earlier digit we have already written.
Code C - [expand] 1 2 3 4 5 6 MAX7219 DIG PIN -> 4K7 RESISTOR -> BASE PIN PNP. BASE PIN OF PNP -> 47K -> +12V +12V -> 300R RESISTOR -> EMITTER PIN OF PNP COLLECTOR PIN OF PNP -> VDD PINS of INDIVIDUAL LED DIGIT MAX7219 SEG PINS -> ULN2003 -> LED SEGMENT PINS.
sample picture attached FYR.
what could be the problem?
thanks in advance.