Interfacing ultrasonic range sensor (HCSR-04) with avr ATmega-32? - c

I am using an ultrasonic range/sonar sensor (HCSR-04) with an AVR ATmega32A. I have written the code understanding the concept of how the sensor works but although the program compiles correctly the device doesn't give any result.
The LCD is showing "out of range" which means PINC1 isn't going high. Is my method for checking if a bit is high or low correct? Should I use the bit_is_set(PORTC,PINC1) function? I am using the default frequency 1 MHz. PINC0 is connected to trig and PINC1 is the echo input. Here is the code:
#include<avr/io.h>
#include<util/delay.h>
#include"lcd.h"
int main(void){
ini_lcd();
TCCR1B|=1<<CS10;
DDRC|=1<<PINC0;
int a=0,b=0;
while(1){
TCNT1=0;
PORTC|=1<<PINC0;
while(TCNT1<100);
PORTC&=~(1<<PINC0);
TCNT1=0;
while(!(PORTC&(1<<PINC1))) && TCNT1<30000) ; // checking if echo has become high and not exceeding the time for max range i.e 5 m
///send_string("out");
b=TCNT1;
if(b<30000){
TCNT1=0;
while(PORTC&(1<<PINC1)); // waiting until the echo become low again
a=TCNT1;
go_to_pos(1,5);
send_int(a/58);
} else {
go_to_pos(1,5);
send_string("out of range");
}
_delay_ms(20);
}
}

The main problem I see in your code that is repeated a few times is how you're trying to read the input I/O line, for example:
while(PORTC&(1<<PINC1)); // waiting until the echo become low again
Should become:
while(PINC&(1<<PINC1)); // waiting until the echo become low again
The PORT registers are the output latches and will either contain the last value written to them or the power-on default value of zero. You need to use the PIN registers to read the current state of the I/O pin.

you need to make the tick counts in TCNT1 = 300000 not 30000 when checking for the Echo pin, since your clock is 1000000 HZ then each 0.1us TCNT1 is incremented by 1 so for 300000 tick you get 30000 us (waiting time) which is equal to the time needed for the echo to travel back at 5 meter (max range for the HCSR04)

Related

I can't understand how to set period of PWM signal

i would like to create a PWM signal. And i want the frequency to be close to 38 khz. My theoretical calculation for period is 26.3 microseconds. So i choose 26 microseconds. And i can observe my signal.
But i don't understand how my code works properly :)
(My clock frequency is 1MHz so my clock signal is 1 microseconds )
if((P1IN & BIT3)!=BIT3) { // if button is pressed
for(i=0;i<692;i++){ // pwm signal's duration is 9ms
P2OUT^=0x01; // switch from 1 to 0 or vice versa
__delay_cycles(4);
}
P2OUT=0x00;
}
my calculation is:
i <692,i++,P2OUT^=0x01; // total 3 cycles
__delay_cycles(4); //total 4 cycles
so 4+3=7. but i'm confused because i think it should be 13 not 7
(here is my signal)
https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/166/f0fd36b0_2D00_bebd_2D00_4a31_2D00_b564_2D00_98962cf4749e-_2800_1_2900_.jpg
You can not calculate cycles based on C or C++ code. you need to check the assembly file(s) generated during the compilation of the program. Based on your compiler (which you did not mention) you can pass some some compiler parameters/switches to ask the compiler to leave the generated assembly file(s) in place for you to check the generated assembly instructions. but basically the for loop would have a jump instruction which may take 2/3 cycles and you did not calculate that.
I recommend that you later check the number of cycles of each instruction from the micro controller datasheet.
The posted code (per your calculations) switches the output every ~7cycles. and does this 692 times. For a total of 346 total cycles, however the total pulse ON time is only ~7cycles. Suggest:
if((P1IN & BIT3)!=BIT3)
{ // if button is pressed
// start pwm signal
P2OUT = 0x01;
for(int i=0; i< (9*1000);i++) // may need to be adjusted
{ // so pwm signal's duration is 9ms
_delay( 1 );
}
// stop pwm signal
P2OUT=0x00;
// wait for button to be released
while( P1IN & BIT3)!=BIT3 ){;}
}
I'm not familiar with your microcontroller's PWM details, However, most have an initialization to set how fast the PWM timer counts and its start/termination count and if it repeats and if the output is a square wave or a step up or a step down signal and the percentage of ON .vs.OFF time.
However, the posted code indicates the PWM is only a regular GPIO bit.
The posted code indicates the PWM on percentage is to be 50percent. Is this what you want?

How to get millisecond resolution from DS3231 RTC

How to get accurate milliseconds?
I need to calculate the delay of sending data from Arduino A to Arduino B. I tried to use DS3231 but I cannot get milliseconds. What should I do to get accurate milliseconds from DS3231?
The comment above is correct, but using millis() when you have a dedicated realtime clock makes no sense. I'll provide you with better instructions.
First thing in any hardware interfacing project is a close reading of the datasheet. The DS3231 datasheeet reveals that there are five possible frequencies of sub-second outputs (see page 13):
32 KHz
1 KHz
1.024 KHz
4.096 KHz
8.192 KHz
These last four options are achieved by various combinations of the RS1 and RS2 control bits.
So, for example, to get exact milliseconds, you'd target option 2, 1KHz. You set RS1 = 0 and RS2 = 0 (see page 13 of the datasheet you provided) and INTCN = 0 (page 9). Then you'd need an ISR to capture interrupts from the !INT/SQW pin of the device to a digital input pin on your Arduino.
volatile uint16_t milliseconds; // volatile important here since we're changing this variable inside an interrupt service routine:
ISR(INT0_vect) // or whatever pin/interrupt you choose
{
++milliseconds;
if(milliseconds == 999) // roll over to zero
milliseconds = 0;
}
OR:
const int RTCpin = 3; // use any digital pin you need.
void setup()
{
pinmode(RTCpin, INPUT);
// Global Enable INT0 interrupt
GICR |= ( 1 < < INT0);
// Signal change triggers interrupt
MCUCR |= ( 1 << ISC00);
MCUCR |= ( 0 << ISC01);
}
If these commands in setup() don't work on your Arduino, google 'Arduino external interrupt INT0'. I've shown you two ways, one with Arduino code and one in C.
Once you have this ISR working and pin3 of the DS3231 connected to a digital input pin of your choosing, that pin will be activated at 1KHz, or every millisecond. Perfect!
// down in main program now you have access to milliseconds, you might want to start off by setting:
// When 1-second RTC changes seconds:
milliseconds = 0; // So you can measure milliseconds since last second.
That's all there is to it. All you need to learn now is how to set the command register using I2C commands and you're all set.
The C code example gains 1ms every second. Should be:
{
if (milliseconds == 999) // roll over to zero
milliseconds = 0;
else
++milliseconds;
}

How to generate note without library?

I'm trying to generate note for example Do , do's frequency is 523.
I wrote some codes but, i did not work
Systick 8 mhz
void note1(void){ // Note Do
for (int i = 0; i < 523; i++){
GPIOE->ODR = 0x4000;
delay_ms(1);
GPIOE->ODR = 0x0000;
delay_ms(1);
}
}
How can we solve this problem ?
EasyMx Pro v7
I'm calling the function like that
void button_handler(void)
{
note1();
// Clear pending bit depending on which one is pending
if (EXTI->PR & (1 << 0)){
EXTI->PR = (1 << 0);
}
else if (EXTI->PR & (1 << 1)){
EXTI->PR = (1 << 1);
}
}
523 times sending 1 and 0 and delay_ms 1 = 1 ms
1000 = 1 sec
On STM32 (as I can see you have it) you have timers which can be configured as PWM output.
So use timer, set period and prescaler values according to your needed frequency and set duty cycle on channel to 50%.
If you need 523Hz PWM output, then set your timer PWM to 523Hz using prescaler and period value:
timer_overflow_frequency = timer_input_clock /
(prescaler_value + 1) /
(period_value + 1) ;
Then, for your output channel set value half of timer period value.
For standard peripheral library, tutorial can be used from here:
https://stm32f4-discovery.net/2014/05/stm32f4-stm32f429-discovery-pwm-tutorial/
Link from unwind for Cube https://electronics.stackexchange.com/questions/179546/getting-pwm-to-work-on-stm32f4-using-sts-hal-libraries
You appear to have a fundamental misunderstanding. In your code note1(), the value 523 will affect only the duration of the note, nit its frequency. With 1ms high, 1ms low repeated 523 times you will generate a tone of approximately 500Hz for approximately 1.43 seconds. I say "approximately" because there will be some small overhead in the loop other then the time delays.
A time delay resolution 1ms is insufficient to generate an accurate tone in that manner. To do it in the manner you have, each delay would need to be 1/2f seconds, so for 523Hz approximately 956ms. The loop iteration count would need to be ft, so for say .25 seconds, 131 iterations.
However if button_handler() is as it appears to be an interrupt handler, you really should not be spending 1.46 seconds in an interrupt handler!
In any event this is an extraordinarily laborious, CPU intensive and inaccurate method of generating a specific frequency. The STM32 on your board is well endowed with hardware timers with direct GPIO output that will generate the frequency you need accurately with zero software over head. Even if none of the timers map to a suitable GPIO output that you need to use, ou can still get one to generate an interrupt at 1/2f and toggle the pin in the interrupt handler. Either way that will leave the processor free to do useful stuff while the tone is being output.

Stopwatch using a ATMEL 2549 Microcontroller

i am trying to understand a program but i have some questions, maybe you can help me. The microcontroller used is a ATMEL 2549 - 8bit. Thank you in advance.
Atmel-2549 8-bit AVR Microcontroller ATmega640 1280-1281-2560-2561 datasheet
Set up a stop watch with the following features:
• There are three push buttons: START, STOP, and RESET
• Your system generates an interrupt every 100ms by using Timer1.
• There is an LCD at port A. Use the usual library for controlling the
LCD!
• On the LCD, you display the time that has elapsed since the START
button was pushed. Show minutes, seconds and tenth of seconds.
• After 59 min 59.9 s, the display starts from scratch again.
#include <stdint.h>
#include <avr/io.h>
#include "lcd.h"
#include <stdio.h>
#include <avr/interrupt.h>
void timer1_config(void);
void exinterrupt_config(void);
void send_string(void);
display myLCD;
volatile char text[20];
volatile uint8_t minute=0,sekunde=0,zehnt=0;
ISR(TIMER1_COMPA_vect) { //Interrupt for a timer with minute, second and decisecond.
zehnt++; //from 0 to 59min 59,9sec. After that time is elapsed,
if (zehnt>9) { //it should be showed on LCD display.
zehnt=0;
sekunde=sekunde+1;
}
if (sekunde>59) {
sekunde=0;
minute=minute+1;
}
if (minute>59) {
minute=0;
sekunde=0;
zehnt=zehnt+1;
}
send_string();
}
ISR(INT0_vect) { //Interrupt for starting the timer.
// --- No. *1 ---
TCCR1B|= (1<<CS11);
}
ISR(INT1_vect) { //Interrupt for stopping the timer.
TCCR1B&=~((1<<CS10)|(1<<CS11)|(1<<CS12));
}
ISR(INT2_vect) { //Interrupt for resetting the timer.
minute=0; //Sets everything to 0 and shows time on LCD display.
sekunde=0;
zehnt=0;
TCNT1=0;
send_string();
}
int main(void) {
// --- No. *2 ---
DDRD&=~((1<<PIN0)|(1<<PIN1)|(1<<PIN2));
timer1_config(); //Load all three functions.
exinterrupt_config();
send_string();
lcd_init(&myLCD ,&PORTA); //Start the LCD display on port A.
lcd_send_string(&myLCD,"-------Watch-------",1,1);
sei();
for(;;){};
return(0);
}
void timer1_config(void){
TCCR1B|=(1<<WGM12);
OCR1A=12499;
// --- No. *3 ---
TIMSK1|=(1<<OCIE1A);
}
void exinterrupt_config(void){
EIMSK|=((1<<INT0)|(1<<INT1)|(1<<INT2)); //Enable all 3 interrupts.
// --- No. *4 ---
EICRA|=((1<<ISC01)|(1<<ISC11)|(1<<ISC21));
}
void send_string(void){ //Sends text to LCD display.
sprintf(text,"%i.min %i.sek %i.zehnt",minute,sekunde,zehnt);
lcd_send_string(&myLCD,text,3,1);
}
1: I understand this is the command to make the timer start counting, but on the description from the datasheet it says "clkI/O/8 (From prescaler)" for setting the bit CS11 high. I cant understand it and how it works.
2: Is it setting the bits from DDRD to input (0)? If so, why is it being done if port D inst even being used?
3: I dont understand what it does!
4: The description from the datasheet says "The falling edge of INTn generates asynchronously an interrupt request", but i dont really get what it does. Whats the difference to "The rising edge of INTn generates asynchronously an interrupt request"?
Thank you again!
1: Setting CS11 High
From Table 17-6, it really sets the clock to clk(I/O)/8. That means it will increment the internal counter on every eighth tick of the internal I/O clock. Maybe you couldn't count every tick in the timer's register in a second, so you need to prescale it.
2: Setting DDRD bits to input
Those are for the buttons. The buttons must be on PIND of your panel, one bit for each button. Although the program does not read PIND, the external interrupt handler does, so the data direction must be set up accordingly.
Buttons, switches are inputs, leds are outputs. It depend's on your developer panel on which ports are they wired.
3: Setting up TIMSK1
§17.11.36
• Bit 1 – OCIEnA: Timer/Countern, Output Compare A Match Interrupt
Enable When this bit is written to one, and the I-flag in the Status
Register is set (interrupts globally enabled), the Timer/Countern
Output Compare A Match interrupt is enabled. The corresponding
Interrupt Vector (see “Interrupts” on page 101) is executed when the
OCFnA Flag, located in TIFRn, is set.
The timer peripherial can operate in different modes. This setting is related to output compare mode, and it will tell the hardware to issue an interrupt when the timer's internal counter reaches a limit (the limit is set in OCR1A).
The timer is set to CTC (Clear Timer on Compare) mode in TCCR1B (Table 17-2), so it restarts counting when the limit is reached.
4: Falling edge
A falling edge is when a signal goes from high to low. A rising edge is when the signal goes from low to high. These buttons are usually Active-LOW, so a falling edge means the button is pressed. (and a rising edge means the button is released)

CCS PICC CCP settings

(I'll gladly post code if someone can point out how to paste it in here without using the 4 space indentation system that doesn't work)
Hello folks
After ~9Hours racking by brains, I can't find an answer or find where my calculations are going wrong... but they are.
I have a circuit built using a microchip 18F2550 microcontroller.
I am using this circuit to measure the delay between 2 signals and am using the 2 CCP registers in capture mode.
This all works and the result is sent to the PC (over USB serial) all dandy, but the results are wrong.
I have to apply a gain of ~16000 to any results to get somewhere near the delay presented to the pins.
I have the delay set in the line
Timer1 is set as an internal
Timer3 is disabled
relevant interrupts are enabled
and the main routine runs continuously.
When I get a rising edge detection on the CCP1 pin, the interrupt is configured to reset timer1 to zero as well as the overflow counter
#INT_CCP1
void ccp1_isr() // Captures the rising edge of CCP1 pin.
{
if(timing==FALSE){ // only do this on the edge, any bouncing will reset timers etc.
set_timer1(0);
T1_Overflow = 0;
Pulse_Time = 0;
timing = 1; // Set flag to indicate timing.
output_high(BLUE_LED);
}
}
the timing flag ensures the times cannot be reset by another pulse on the CCP1 pin.
Timer1 should then be reset and start counting as normal. Every time it rolls around by 65535 (16bit device) another interrupt is fired after which the amount of overflows are incremented.
#INT_TIMER1
void isr()
{
T1_Overflow++;
}
Finally, when the input pin on CCP2 goes high, the CCP_2 interrupt is triggered. This captures the value of the CCP register (which is the value of Timer0 at the time the interrupt was fired) and the overflow register.
#INT_CCP2
void ccp2_isr()
{
if(timing == TRUE){ // only output this when preceded by CCP1
if(Count_Done == FALSE) // do this once only
{
Count_Done = TRUE; // and also flag to the main routine to output data to the terminal.
Pulse_time = CCP_2;
Pulse_Overflow = T1_Overflow;
measureCount++; // increment the number of measures.
}
output_low(BLUE_LED);
timing = FALSE;
}
}
CCP1 can now start responding to the inputs again.
The idea of this is that every time I get a pulse of one input at CCP1 followed by CCP2, a string is sent to the terminal with a counter, the number of overflows and the time left in the timer.
while(TRUE) // do forever while connected
{
usb_task(); // keep usb alive
if(Count_Done == TRUE)
{
printf(usb_cdc_putc, "%lu , %lu , %lu \r\n",measureCount, pulse_time, pulse_overflow);
Count_Done = FALSE;
}
so, I should get an output to the terminal of something like "1,61553,35" for a ~12ms delay between CCP1 and CCP2.
The problem is that these are the results I am getting for a 200ms pulse provided to the circuit. (Verified twice)
so where am I going wrong.
I have a 48MHZ Clock with no prescaler which implies a cycle every 20ns.
Divide by for 4 instructions per cycle for the clock which implies 5.2ns every cycle
16 bit timer which implies rollover every 65535*5.2ns = 341us per rollover.
when you do the calculations (0.000341*pulse_overflow)+pulse_time*(5.2*(10^-9))
then the above data gives 0012.27ms and not the 200ms provided.
Can anyone point out where I am going wrong with these calculations???
Your error is in "Divide by for 4 instructions per cycle for the clock which implies 5.2ns every cycle"
The counter ticks once every 4 cycles, not 4 times per cycle. So, the correct calculations are:
2.08333E-08 s/cycle of osc
8.33333E-08 s/tick of timer
0.005461333 s/rollover
You are off by a factor of 16.

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