elec_mech
- 10th January 2009, 21:17
Hello Ladies & Gents,
I'm attempting to make a countdown timer using eight seven-segment digits controlled by a MAX7221. Upon initial breadboarding I got it to work. However, I decided to change some wiring to have the digit order better agree with the software and it hasn't worked since. At one point I accidently hooked up the current limiting resistor to the MAX7221 to the Vcc line. I've replaced the MAX7221 with a new one. I bought new breadboards and build a new circuit from scratch, also without luck. I'm blinking an LED to indicate when the program starts and stops and that works fine, so the program is running. I've also tried placing LEDs on the data, clock and enable lines to check the I/O pins and they work fine. I noticed in a previous topic that the there may be noise and added 10uF and 0.1uF capacitors - still no luck. I've included the code and a schematic of what I've build.
PORTA = $00 ' Set all port a pins low
PORTC = $00 ' Set all port c pins low
define OSC 4 ' Tell the program the oscillator is running at 4 MHz
TRISA = %11111111 ' Make all port A pins inputs
TRISC = %11100000 ' Make port C pins 4 & 5 inputs and the rest outputs
PORTA = $00 ' Set all port a pins to low
PORTC = $00 ' Set all port c pins to low
CMCON.0 = 1 ' Turn off comparator module
CMCON.1 = 1 ' Turn off comparator module
CMCON.2 = 1 ' Turn off comparator module
ADCON0.6 = 0 ' Use VDD as analog reference
ANSEL = %00001000 ' Use AN3 as analog input and set all other analog
' inputs to digital pins
CS_Max VAR PORTC.3 ' Chip select for MAX7221 IC
CS_DS VAR PORTC.2 ' Chip select for DS1302 IC
SPI_CLK VAR PORTC.0 ' Clock for SPI communication
SPI_SDO VAR PORTC.1 ' Serial Data Out for SPI communication
Tog_Switch VAR PORTA.1 ' Toggle switch
Sel_Switch VAR PORTA.2 ' Select switch
b1 VAR byte ' Button variable for toggle switch
b2 VAR byte ' Button variable for select switch
'************************************************* **********************************************
HIGH CS_Max
pause 500 ' Wait for 500ms
Main:
HIGH PORTC.4
PAUSE 500
LOW PORTC.4
PAUSE 500
LOW CS_Max ' Enable the MAX7221 to receive data
SHIFTOUT SPI_SDO, SPI_CLK, 1, [$0F01\16] ' Turn on Display Test (light up all LEDs on all eight digits)
HIGH CS_Max ' Pull chip select to MAX7221 high to act on transmitted data
PAUSE 5000 ' Wait one second
LOW CS_Max ' Enable the MAX7221 to receive data
SHIFTOUT SPI_SDO, SPI_CLK, 1, [$0F00\16] ' Turn off Display Test
HIGH CS_Max ' Pull chip select to MAX7221 high to act on transmitted data
PAUSE 1000 ' Wait one second
HIGH PORTC.4
PAUSE 500 ' Wait one second
LOW PORTC.4
PAUSE 500
END ' End Program
I do not have the DS1302, buttons or photoresistor connected yet as I'm stuck trying to get the MAX7221 to work. Outside of ESD problems or gremlins, I'm stuck. Any advice is greatly appreciated.
I'm attempting to make a countdown timer using eight seven-segment digits controlled by a MAX7221. Upon initial breadboarding I got it to work. However, I decided to change some wiring to have the digit order better agree with the software and it hasn't worked since. At one point I accidently hooked up the current limiting resistor to the MAX7221 to the Vcc line. I've replaced the MAX7221 with a new one. I bought new breadboards and build a new circuit from scratch, also without luck. I'm blinking an LED to indicate when the program starts and stops and that works fine, so the program is running. I've also tried placing LEDs on the data, clock and enable lines to check the I/O pins and they work fine. I noticed in a previous topic that the there may be noise and added 10uF and 0.1uF capacitors - still no luck. I've included the code and a schematic of what I've build.
PORTA = $00 ' Set all port a pins low
PORTC = $00 ' Set all port c pins low
define OSC 4 ' Tell the program the oscillator is running at 4 MHz
TRISA = %11111111 ' Make all port A pins inputs
TRISC = %11100000 ' Make port C pins 4 & 5 inputs and the rest outputs
PORTA = $00 ' Set all port a pins to low
PORTC = $00 ' Set all port c pins to low
CMCON.0 = 1 ' Turn off comparator module
CMCON.1 = 1 ' Turn off comparator module
CMCON.2 = 1 ' Turn off comparator module
ADCON0.6 = 0 ' Use VDD as analog reference
ANSEL = %00001000 ' Use AN3 as analog input and set all other analog
' inputs to digital pins
CS_Max VAR PORTC.3 ' Chip select for MAX7221 IC
CS_DS VAR PORTC.2 ' Chip select for DS1302 IC
SPI_CLK VAR PORTC.0 ' Clock for SPI communication
SPI_SDO VAR PORTC.1 ' Serial Data Out for SPI communication
Tog_Switch VAR PORTA.1 ' Toggle switch
Sel_Switch VAR PORTA.2 ' Select switch
b1 VAR byte ' Button variable for toggle switch
b2 VAR byte ' Button variable for select switch
'************************************************* **********************************************
HIGH CS_Max
pause 500 ' Wait for 500ms
Main:
HIGH PORTC.4
PAUSE 500
LOW PORTC.4
PAUSE 500
LOW CS_Max ' Enable the MAX7221 to receive data
SHIFTOUT SPI_SDO, SPI_CLK, 1, [$0F01\16] ' Turn on Display Test (light up all LEDs on all eight digits)
HIGH CS_Max ' Pull chip select to MAX7221 high to act on transmitted data
PAUSE 5000 ' Wait one second
LOW CS_Max ' Enable the MAX7221 to receive data
SHIFTOUT SPI_SDO, SPI_CLK, 1, [$0F00\16] ' Turn off Display Test
HIGH CS_Max ' Pull chip select to MAX7221 high to act on transmitted data
PAUSE 1000 ' Wait one second
HIGH PORTC.4
PAUSE 500 ' Wait one second
LOW PORTC.4
PAUSE 500
END ' End Program
I do not have the DS1302, buttons or photoresistor connected yet as I'm stuck trying to get the MAX7221 to work. Outside of ESD problems or gremlins, I'm stuck. Any advice is greatly appreciated.