duration NOP instruction
Posted:
Fri Dec 19, 2014 9:28 amby nicoverduin
Hi all
I am trying to figure out how long does it take the ESP8266ex to process a NOP instruction. I need some strict timing pulses and it would either be using the interrupt timer or hard coded. I have been digging through some of the LX106 manuals... but I am lost
Re: duration NOP instruction
Posted:
Fri Dec 19, 2014 11:57 amby joostn
In my tests
takes 1/80000000 second, i.e. one clock pulse.
Now if you find out how to use interrupt timers please let me know.
Re: duration NOP instruction
Posted:
Fri Dec 19, 2014 1:46 pmby nicoverduin
This is from a file (io.c) in esphttpd server project from Jeroen Domburg
Code: Select all**
* @file io.c
* Handles all the IO functions within this program
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain
* this notice you can do whatever you want with this stuff. If we meet some day,
* and you think this stuff is worth it, you can buy me a beer in return.
* ----------------------------------------------------------------------------
*/
//
// includes
//
#include "espmissingincludes.h"
#include "c_types.h"
#include "user_interface.h"
#include "espconn.h"
#include "mem.h"
#include "osapi.h"
#include "gpio.h"
//
// pin definitions
//
#define LEDGPIO 2
#define BTNGPIO 0
static ETSTimer resetBtntimer; // counts the interrupts
/**
* @name resetBtnTimerCb(void *arg)
* @param arg parameter is ignored here
* timer function called based on the timer function
*/
static void ICACHE_FLASH_ATTR resetBtnTimerCb(void *arg) {
static int resetCnt=0;
//
// check if the button is pressed
//
if (!GPIO_INPUT_GET(BTNGPIO)) {
//
// increment the counter
//
resetCnt++;
} else {
//
// check if more than 3 seconds are pressed
//
if (resetCnt>=6) { // 3 sec pressed as the timer is set for once every 500mS
//
// disconnect from the LAN
//
wifi_station_disconnect();
//
// reset to AP + STA mode
//
wifi_set_opmode(0x3); //reset to AP+STA mode
os_printf("Reset to AP mode. Restarting system...\n");
//
// restart system
//
system_restart();
}
//
// reset the counter
//
resetCnt=0;
}
}
/**
* @name ioInit()
* Initialize IO pins and timers
*/
void ioInit() {
//
// select pins GPIO0 and GPIO2
//
PIN_FUNC_SELECT(PERIPHS_IO_MUX_GPIO2_U, FUNC_GPIO2);
PIN_FUNC_SELECT(PERIPHS_IO_MUX_GPIO0_U, FUNC_GPIO0);
//
// Set the button as Input and LED as output
//
gpio_output_set(0, 0, (1<<LEDGPIO), (1<<BTNGPIO));
//
// turn off timer
//
os_timer_disarm(&resetBtntimer);
//
// set the timer call back function
//
os_timer_setfn(&resetBtntimer, resetBtnTimerCb, NULL);
//
// turn timer on to trigger each .5 second
//
os_timer_arm(&resetBtntimer, 500, 1);
}
Re: duration NOP instruction
Posted:
Sun Dec 21, 2014 3:36 pmby RogerClark
Isn't there a os_delay_us() function that does this.
But for very accurate timing, you are better off declaring a using a for loop, and declare the loop variable as volatile.
That way the compiler is forced to generate the code even if the for loop is empty.