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At least you're being real, I admire that. I wish others could acknowledge my algorithm.
How do I modify my PIC microcontroller program to deliver 150 hz also with the existing 1hz output
- Thread starter Arjune
- Start date
From the 150 Hz output you can implement a small bit of code that counts to 75, which is half of 150 and toggles another GPIO pin. you'll get 75 cycles where the selected GPIO pin is high and 75 where it is low. I know you are having difficulty at the moment, but I encourage to keep coming back to things you don't understand. I promise that one day an imaginary light bulb will illuminate, and you will finally understand what is going on. If it will help, I can provide a clean version of the ISR and the initialization for you to study instead of telling you what changes to make.
Last edited:
Here is the modification for doing 150 Hz
The modifed lines are numbers 23 & 24 and the comment/description of what I did is on lines 3 thru 6. Let me know if this helps. If it does, I'll try to add a 1 HZ. option on another GPIO pin. If this does not help you then, sorry, but I have little to no clue what will be helpful.
Code:
#include <xc.h>
/*
* Modify for 150 Hz Output
* Timer 1 Reload value changes from 0x3CB0 (decimal 15536) to 0xFD65 (decimal 667)
*/
// Configuration Bits: 16MHz HS Crystal, Watchdog Off, MCLR On, LVP Off
#pragma config FOSC = HS, WDTE = OFF, PWRTE = ON, MCLRE = ON, BOREN = OFF, LVP = OFF, CPD = OFF, CP = OFF
#define _XTAL_FREQ 16000000 // 16 MHz Crystal
#define CLOCK_OUT PORTBbits.RB0
unsigned int timer_counter = 0;
void __interrupt() isr(void) {
if (PIR1bits.TMR1IF) { // Check Timer 1 Overflow Flag
// Preload Timer 1 for 100ms delay:
// Instruction frequency = 16MHz / 4 = 4MHz
// Timer 1 with 1:8 Prescaler = 500kHz (2us per tick)
// 100ms / 2us = 50,000 ticks.
// Preload value = 65536 - 50000 = 15536 (0x3CB0)
TMR1H = 0xFD;
TMR1L = 0x65;
timer_counter++;
if (timer_counter >= 5) { // 10 * 100ms = 1 second
CLOCK_OUT = ~CLOCK_OUT; // Toggle the pin
timer_counter = 0;
}
PIR1bits.TMR1IF = 0; // Clear interrupt flag
}
}
void main(void) {
CMCON = 0x07; // Disable comparators to use PORTA/B as digital I/O
TRISBbits.TRISB0 = 0; // Set RB0 as output
CLOCK_OUT = 0;
// Timer 1 Configuration
T1CONbits.T1CKPS = 0b11; // 1:8 Prescaler
T1CONbits.TMR1CS = 0; // Internal clock (Fosc/4)
TMR1H = 0x3C; // Initial preload
TMR1L = 0xB0;
// Interrupt Configuration
PIE1bits.TMR1IE = 1; // Enable Timer 1 interrupt
INTCONbits.PEIE = 1; // Enable peripheral interrupts
INTCONbits.GIE = 1; // Enable global interrupts
T1CONbits.TMR1ON = 1; // Start Timer 1
while (1) {
// Main loop remains empty; logic is handled in ISR
}
}With TMR1H = 0xFD; and TMR1L = 0x65;, according to my oscilloscope, I get 74.67hz--half of what I wanted.
That is interesting. I might need to start drawing better pictures for myself. I cannot be there to look over your shoulder to find the discrepancy, I'll try to go over my figures to see if I can find the problem.
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WBahn has a mantra about checking the units in a calculation. Doing that I found my mistake in converting "time" with units of seconds into "time" with units of clock ticks. In our case a click tic is 2 µsec in duration. Here is the revised code for 150 Hz.
Code:
#include <xc.h>
/*
* Modify for 150 Hz Output
* Timer 1 Reload value changes from 0x3CB0 (decimal 15536) to 0xFEB3 (decimal 333)
*/
// Configuration Bits: 16MHz HS Crystal, Watchdog Off, MCLR On, LVP Off
#pragma config FOSC = HS, WDTE = OFF, PWRTE = ON, MCLRE = ON, BOREN = OFF, LVP = OFF, CPD = OFF, CP = OFF
#define _XTAL_FREQ 16000000 // 16 MHz Crystal
#define CLOCK_OUT PORTBbits.RB0
unsigned int timer_counter = 0;
void __interrupt() isr(void) {
if (PIR1bits.TMR1IF) { // Check Timer 1 Overflow Flag
// Preload Timer 1 for 100ms delay:
// Instruction frequency = 16MHz / 4 = 4MHz
// Timer 1 with 1:8 Prescaler = 500kHz (2us per tick)
// 100ms / 2us = 50,000 ticks.
// Preload value = 65536 - 50000 = 15536 (0x3CB0)
TMR1H = 0xFE;
TMR1L = 0xB3;
timer_counter++;
if (timer_counter >= 5) { // 10 * 100ms = 1 second
CLOCK_OUT = ~CLOCK_OUT; // Toggle the pin
timer_counter = 0;
}
PIR1bits.TMR1IF = 0; // Clear interrupt flag
}
}
void main(void) {
CMCON = 0x07; // Disable comparators to use PORTA/B as digital I/O
TRISBbits.TRISB0 = 0; // Set RB0 as output
CLOCK_OUT = 0;
// Timer 1 Configuration
T1CONbits.T1CKPS = 0b11; // 1:8 Prescaler
T1CONbits.TMR1CS = 0; // Internal clock (Fosc/4)
TMR1H = 0xFE; // Initial preload
TMR1L = 0xB3;
// Interrupt Configuration
PIE1bits.TMR1IE = 1; // Enable Timer 1 interrupt
INTCONbits.PEIE = 1; // Enable peripheral interrupts
INTCONbits.GIE = 1; // Enable global interrupts
T1CONbits.TMR1ON = 1; // Start Timer 1
while (1) {
// Main loop remains empty; logic is handled in ISR
}
}
you could just make a loop and use a pause timer / counter
it would then be interupted by anthing else you may be doing...
It looks like things are OK now--I get 148.98hz on my oscilloscope. It sounds that way too on the headphones. I clocked one of my clocks externally with it and the minutes are switching at a nominal rate so I know from intuition the frequency is right.
If you care to experiment, you can add or subtract 1 from the Timer 1 reload value; local variations in crystal frequency and temperature can be corrected for in this fashion. Raising the reload valu by 1 to 0xFEB4 should raise the frequency and lowering it to 0xFEB2 should lower it a bit.
Its ok, for simulation.
Code:
// PIC16F627A Configuration Bit Settings
// 'C' source line config statements
// CONFIG
#pragma config FOSC = HS // Oscillator Selection bits (HS oscillator: High-speed crystal/resonator on RA6/OSC2/CLKOUT and RA7/OSC1/CLKIN)
#pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = ON // Power-up Timer Enable bit (PWRT enabled)
#pragma config MCLRE = OFF // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is digital input, MCLR internally tied to VDD)
#pragma config BOREN = ON // Brown-out Detect Enable bit (BOD enabled)
#pragma config LVP = OFF // Low-Voltage Programming Enable bit (RB4/PGM pin has digital I/O function, HV on MCLR must be used for programming)
#pragma config CPD = ON // Data EE Memory Code Protection bit (Data memory code-protected)
#pragma config CP = ON // Flash Program Memory Code Protection bit (0000h to 03FFh code-protected)
// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.
#include <xc.h>
#include <stdint.h>
#define _XTAL_FREQ 16000000
#define ONE_HZ_PIN PORTBbits.RB0
#define OHF_HZ_PIN PORTBbits.RB3
volatile uint16_t s1 = 0;
volatile uint8_t s2 = 0;
volatile uint8_t one_Hz_flag = 0;
volatile uint8_t ohf_Hz_flag = 0;
const uint8_t tmr1_h = 254;
const uint8_t tmr1_l = 112;
/*
*
*/
void mcu_Init(void)
{
CMCONbits.CM = 0b111;
PORTA = 0xFF;
PORTB = 0xFF;
TRISA = 0x00;
TRISB = 0x00;
}
/*
* http://eng-serve.com/pic/pic_timer.html
*/
void isr_Init(void)
{
//Timer1 Registers Prescaler= 1 - TMR1 Preset = 65136 - Freq = 10000.00 Hz - Period = 0.000100 seconds
T1CONbits.T1CKPS1 = 0b0; // bits 5-4 Prescaler Rate Select bits
T1CONbits.T1CKPS0 = 0b0; // bit 4
T1CONbits.T1OSCEN = 0b1; // bit 3 Timer1 Oscillator Enable Control bit 1 = on
T1CONbits.nT1SYNC = 0b1; // bit 2 Timer1 External Clock Input Synchronization Control bit...1 = Do not synchronize external clock input
T1CONbits.TMR1CS = 0b0; // bit 1 Timer1 Clock Source Select bit...0 = Internal clock (FOSC/4)
T1CONbits.TMR1ON = 0b1; // bit 0 enables timer
TMR1H = tmr1_h; // preset for timer1 MSB register
TMR1L = tmr1_l; // preset for timer1 LSB register
// Interrupt Registers
INTCON = 0; // clear the interrpt control register
INTCONbits.TMR0IE = 0b0; // bit5 TMR0 Overflow Interrupt Enable bit...0 = Disables the TMR0 interrupt
PIR1bits.TMR1IF = 0b0; // clear timer1 interupt flag TMR1IF
PIE1bits.TMR1IE = 0b1; // enable Timer1 interrupts
INTCONbits.TMR0IF = 0b0; // bit2 clear timer 0 interrupt flag
INTCONbits.GIE = 0b1; // bit7 global interrupt enable
INTCONbits.PEIE = 0b1; // bit6 Peripheral Interrupt Enable bit...1 = Enables all unmasked peripheral interrupts
}
/*
*
*/
void main(void)
{
mcu_Init();
isr_Init();
while(1)
{
if(one_Hz_flag == 1)
{
ONE_HZ_PIN ^= 0b1;
one_Hz_flag = 0;
}
if(ohf_Hz_flag == 1)
{
OHF_HZ_PIN ^= 0b1;
ohf_Hz_flag = 0;
}
}
}
/*
* http://eng-serve.com/pic/pic_timer.html
*/
void interrupt ISR(void)
{
// Timer1 Interrupt - Freq = 10000.00 Hz - Period = 0.000100 seconds
if(PIR1bits.TMR1IF == 0b1) // timer 1 interrupt flag
{
if(s1++ > 4200)
{
one_Hz_flag = 1;
s1 = 0;
}
if(s2++ > 26)
{
NOP();
NOP();
NOP();
ohf_Hz_flag = 1;
s2 = 0;
}
PIR1bits.TMR1IF = 0b0; // interrupt must be cleared by software
PIE1bits.TMR1IE = 0b1; // reenable the interrupt
TMR1H = tmr1_h; // preset for timer1 MSB register
TMR1L = tmr1_l; // preset for timer1 LSB register
}
}
/*----------------------------------------------------------------------------*/Since I'm satisfied with the ~150hz, what about the 1hz output in addition.? Can you show me what the code is and where to add it in the program? I should mention that my original code caused a 1 second per day slowdown of the 1hz. I'm thinking of using a 32,768 hz crystal in the future.
This program will provide 1hz and ~150hz outputs?
I only have a very limited of understanding of C programming (I work with assembler.) but I think mehmetbey's code will give exactly 1 Hz output and very close to 150 Hz output. (Both of these limited by the accuracy of the crystal.)
I suggest changing to a 15 Mhz crystal and then both frequencies can be achieved by dividing 15 Mhz by integers.
Les
I suggest changing to a 15 Mhz crystal and then both frequencies can be achieved by dividing 15 Mhz by integers.
Les
drjohsmith
- Joined Dec 13, 2021
- 1,630
now do ypu understand how the interupt code works ?
drjohsmith
- Joined Dec 13, 2021
- 1,630
how are you aiming to use a 32.768 Khz crystal?
what is this project were doing for you ?
I'm not inclined to learn about it because there's too much pessimism about my ability but eventually I may have to learn about it. If you ask me I think the logic of intelligence was changed by the Antichrist and I was not informed about it that is why it is difficult for me to learn. A new way of understanding was not programmed in my mind.
I plan to use the 32,768hz crystal with the same microcontroller and I'm planning to build another clock that is why I'm inquiring in the forum. Wouldn't this Crystal be more accurate for one hertz. ?
You can get a precise signal by changing the values in the variables s1 and s2. Try it and write me the result.
Do not change the pin value in the interrupt function. It would be more convenient to simply change the values of the variables and track them in the main function.
As @LesJones said; Working with crystals of three and multiples of three will simplify the calculations even more.
External factors (temperature, magnetic fields, supply voltage, etc.) may prevent these frequencies from being stable. Doing it using the DS3231/32's signal output can be more precise.
drjohsmith
- Joined Dec 13, 2021
- 1,630
so your looking at replacing th 16 Mhz crystal with a 32.768 Khz crystal ?
does this processor work with a main crystal of this frequency ?
if it does work at 32.768 Khz ,how will this affect your interupt service routine ?
you are using the isr routine, what do you not understsnd about it ?
maybe you could say how you think the isr does work, so we can help you .
what is the aim of this work ? what college you working at
