Right.
Sorry for the late reply. I did try that code, didn't work as expected. Bitbanging worked and gave me more control too.
void update_display(unsigned char data[])
{
start_bit(); // clock out the start bit
clock_byte(data[0]); // Third Digit
clock_byte(data[1]); // Second Digit
clock_byte(data[2]); // First Digit
DATA_1 = 0; // I don't care about the display I/O pins yet
for (int i = 0; i < 10; i++) // just clocking out the rest of the bits
clock_it();
DATA_1 = 1; // stop bit
clock_it(); // clock in the stop bit
//DATA_ENABLE_1 = 1;
}
void clock_byte(unsigned char data)
{
for (int i = 0; i < 8; i++)
{
#ifdef REAL_DATA
DATA_1 = 1 & data; // AND against data
data = data >> 1; // shift over 1
#endif
#ifndef REAL_DATA
DATA_1 = 1;
#endif
clock_it();
}
}
void clock_it(void)
{
CLK_1 = 1;
__delay_us(2);
CLK_1 = 0;
}
void start_bit(void)
{
DATA_ENABLE_1 = 1; // enable comms
DATA_1 = 0;
CLK_1 = 0;
DATA_ENABLE_1 = 0;
DATA_1 = 1; // start bit 1 of 36
clock_it();
}/**
Generated Main Source File
File Name:
main.c
Blinks 12.3 at 1 sec intervals
*/
#include "mcc_generated_files/mcc.h"
// Data format for display:
// Byte 0: Sabcdefg Start and segments for digit 1 (MSDig)
// Byte 1: Dabcdefg DP for digit1, segs for digit 2
// Byte 2: Dabcdefg DP for digit 2, segs for digit 3
// Byte 4: Dooooooo DP for digit 3, output pins 4-10
// Byte 5: ooo00000 output pins 11-13, remainder of bits MUST be 0
// Segment patterns that show 12.3 on display and PIN13 high (hopefully)
uint8_t segs[5] = {0b10110000, 0b01101101, 0b11111001, 0x00,0b00100000};
uint8_t Zsegs[5]= {0x80,0,0,0,0}; // start bit and all segs off
// Sends byte to SPI, waits for BF indicating byte has been transmitted.
// Can pre-check BF if desired and/or read SSP1BUF to prevent WCOL.
void sendSPI(uint8_t c){
SSP1BUF = c;
while(SSP1STATbits.BF == 0);
//SSP1BUF; // opt. read SSP1BUF to avoid WCOL
}
void main(void)
{
uint8_t k;
// initialize the device
SYSTEM_Initialize(); // MCC init IO
// Manual SPI init:
RC7PPS = 0b10001; // using RC7 as SDO.
RB6PPS = 0b10000; // using RB6 as CLK
SSP1CONbits.SSPM = 0b0010; // SPI master mode with a clock of Fosc/64
SSP1CONbits.CKP = 0; // clock idle is 0
SSP1STATbits.CKE = 1; // clocks data on rising edge of clock
SSP1CON1bits.SSPEN = 1;
SSPOV = 0;
while (1)
{
// show 12.3
ENABLE__SetLow(); // my ENABLE is RC4
for (k=0; k < 5; k++){ // send segment image
sendSPI(segs[k]);
}
ENABLE__SetHigh();
__delay_ms(1000);
// All off
ENABLE__SetLow();
for (k=0; k < 5; k++){ // send segment image
sendSPI(Zsegs[k]);
}
ENABLE__SetHigh();
__delay_ms(1000);
}// while
}// mainThanks for checking in again, I think I did the exact opposite when dealing with digital I/O. Reading from LATx and writing to PORTx. I could be wrong, still learning, but I remember hearing you never write to LATx and always to PORTx. Also, my VLED was about 2.5 but the brightness was turned all the way up. Still not too sure how that part of the display works, the datasheet circuit shows what looks like a poor attempt at a voltage divider. Can you clear that up for me?
You always write to LATx and read from PORTx. LATx accesses the output flip-flops and PORTx accesses the pin logic level for inputs. Likewise, you always do a bsf,bcf etc to LATx, never to PORTx. Note that you can specify PORTx for both reads and writes but that can lead to problems. LATx for writes. PORTx for reads - always. That will keep you out of trouble.
Thanks a ton. Now that I know that pin 18 relies on current input and not voltage input things are much clearer.You always write to LATx and read from PORTx. LATx accesses the output flip-flops and PORTx accesses the pin logic level for inputs. Likewise, you always do a bsf,bcf etc to LATx, never to PORTx. Note that you can specify PORTx for both reads and writes but that can lead to problems. LATx for writes. PORTx for reads - always. That will keep you out of trouble.
Brightness and VLED are different things:
VLED supplies the LED current drivers. It is unfortunate that it it is not internally derived from VDD but that's the way it is - this is an old part. I used an LM317T with R1=240 and R2=390 for about 3.3VLED. The segments are driven by constant-current generators whose current is a function of the current injected into pin 18, the 'BRIGHTNESS' pin. They get their power from VLED, not VDD, so VLED has to be able to supply enough current.
The 'BRIGHTNESS' control shown in the datasheet is a variable resistor, not a voltage divider. It varies the current injected into pin 18. The LED current is approx 25 times this current and there is an internal series resistance of 400 ohms. I used a 9.1K resistor from Vdd (+5V) to pin 18. My LED segment current is thus:
25 * (5v/(9100+400)) ~= 13ma/segment.
On yours, connecting directly to +5V gives:
25 * (5V/400) = 31.25ma/segment.
Hope that helps!
by Jake Hertz
by Jake Hertz
by Aaron Carman
by Duane Benson
