Creating accurate delay between 2 pulses on different pins.

[Voidim]

Greetings, i
am new to the esp32. At first glance i though that 240mhz can get me really accurate delays, but turns out it uses 80mhz timer clock, and i have to use divider = 2 so it is 40mhz at the end(25ns each clock), and i cant make my code work.

I have a esp-wroom-32 module(esp32 dev module) and use arduino IDE, my task is to generate 2 pulses on different pins with as much accuracy as possible:
1) make GPIO_NUM_2 and GPIO_NUM_4 go HIGH
2)Generate single shot pulses on a button press with predefined delay:
2.1) Generate negative pulse ~100nS on pin 2 (after that pulse pin2 stays HIGH)
2.2) Wait certain amount of uS: from 3uS to 35uS with precise accuracy.(30nS or less each step i want to increase or decrease delay)
(like to
2.3)Generate another ~100nS pulse on pin4 (after that pulse pin4 stays HIGH)

Currently i came up with the following test code using a timer, but for some reason it does not works as i want:
1)it does not increment delay by 25ns each time (but it starts to work a little better at 22uS or more)
2) minimum delay is ~6.6us, after a while it jumps to 7.7 etc

Code: [Select all] [Expand/Collapse]

1. #include "driver/timer.h"
2. int i = 0; // value added to match each loop
3.  
4. static bool IRAM_ATTR onTimer(void *args) //ISR function
5. {
6. //2nd signal pulse
7.   REG_WRITE(GPIO_OUT_W1TC_REG, BIT4); //GPIO4 LOW(CLEAR)
8.   __asm__ __volatile__ (
9.     " nop\n"
10.     " nop\n"
11.     " nop\n"
12.     " nop\n"
13.     " nop\n"
14.     " nop\n"
15.     " nop\n"
16.     " nop\n"
17.     " nop\n"
18.     " nop\n"
19.     " nop\n"
20.     " nop\n"
21.     " nop\n"
22.     " nop\n"
23.     " nop\n"
24.     " nop\n"
25.     " nop\n"
26.     " nop\n"
27.   );
28.   REG_WRITE(GPIO_OUT_W1TS_REG, BIT4); //GPIO4 HIGH (SET) !!!!!!!!!!!!!!
29.   timer_pause(TIMER_GROUP_0, TIMER_0);
30.   return false;
31. }
32.  
33. void setup() {
34. ////TIMERS SETUP////
35.   timer_config_t config = {
36.     .alarm_en = TIMER_ALARM_EN, //ISR on
37.     .counter_en = TIMER_PAUSE, //timer off after init
38.     //.intr_type = TIMER_INTR_LEVEL, //can be ignored
39.     .counter_dir = TIMER_COUNT_UP, //up
40.     .auto_reload = TIMER_AUTORELOAD_EN, /hardware will load counter value after an alarm event;
41.     .divider = 2, //from 2 to 65536 if 2  = 40mhz =25ns
42.   }; //default clock source is APB (80mhz)
43.  
44.  timer_init(TIMER_GROUP_0, TIMER_0, &config); //init
45. timer_set_counter_value(TIMER_GROUP_0, TIMER_0, 0); //start value
46. timer_set_alarm_value(TIMER_GROUP_0, TIMER_0, 250); //match value
47. timer_isr_callback_add(TIMER_GROUP_0, TIMER_0, onTimer, NULL, 0); // add isr func
48.  timer_enable_intr(TIMER_GROUP_0, TIMER_0); // enable isr
49.  
50. ////PINS SETUP////
51. //set it as gpio
52. gpio_pad_select_gpio( GPIO_NUM_2);
53.  gpio_pad_select_gpio( GPIO_NUM_4);
54. //output
55. gpio_set_direction( GPIO_NUM_2,  GPIO_MODE_OUTPUT);
56.   gpio_set_direction( GPIO_NUM_4,  GPIO_MODE_OUTPUT);
57. //pullup to 3.3
58. gpio_set_pull_mode( GPIO_NUM_2,  GPIO_PULLUP_ONLY);
59.   gpio_set_pull_mode( GPIO_NUM_4,  GPIO_PULLUP_ONLY);
60. //out current = 40ma
61. gpio_set_drive_capability( GPIO_NUM_2,  GPIO_DRIVE_CAP_3);
62.   gpio_set_drive_capability( GPIO_NUM_4,  GPIO_DRIVE_CAP_3);
63. //set as high
64. gpio_set_level( GPIO_NUM_2,  1); //HIGH
65.   gpio_set_level( GPIO_NUM_4,  1); //HIGH
66. }
67.  
68. void loop() {
69. delay(500);
70.  timer_set_alarm_value(TIMER_GROUP_0, TIMER_0, 100+i); //set new match value (100 should be ~2.5uS)
71. timer_set_counter_value(TIMER_GROUP_0, TIMER_0, 0); //reset starting value to 0
72. delay(50);
73.  
74. //1st signal PULSE
75.  REG_WRITE(GPIO_OUT_W1TC_REG, BIT2); //GPIO2 LOW(CLEAR)
76.  __asm__ __volatile__ (
77.     " nop\n"
78.     " nop\n"
79.     " nop\n"
80.     " nop\n"
81.     " nop\n"
82.     " nop\n"
83.     " nop\n"
84.     " nop\n"
85.     " nop\n"
86.     " nop\n"
87.     " nop\n"
88.     " nop\n"
89.     " nop\n"
90.     " nop\n"
91.     " nop\n"
92.     " nop\n"
93.     " nop\n"
94.     " nop\n"
95.   );
96.   REG_WRITE(GPIO_OUT_W1TS_REG, BIT2); //GPIO2 HIGH (SET)
97.  
98. //start timer
99.   timer_start(TIMER_GROUP_0, TIMER_0);
100. }

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Maybe there is better peripheral to do that task?
There is so many ways it seems to do that task: with DMA, RTC, LED pwm, creating some assembly code(i am not familiar with it) that can utilize 240mhz so we can get 4.16ns step.
All those ways just overwhelms me.