NodeMCU firmware for ultrasonic detector on a ESP-12

init.lua

--
-- Simple object avoider robot using the ESP8266/Nodemcu ESP-12
-- Using a L9110s h-bridge and an hc-sr04 with a 1k resistor
-- on the ECHO pin.
--
-- The current ESP only allows for 3 active pwms at any one time.
-- We get around this by the fact we only need 2 at any time. Each
-- direction change resets them pins used as pwm.
--
-- Written by Scott Beasley 2015
-- Open and free to change and use. Enjoy.
--

function setup ( )
   gpio.mode (2, gpio.OUTPUT) -- ia1     - GPIO4
   gpio.mode (3, gpio.OUTPUT) -- ia2     - GPIO0
   gpio.mode (1, gpio.OUTPUT) -- ib1     - GPIO5
   gpio.mode (4, gpio.OUTPUT) -- ib2     - GPIO2

   gpio.mode (8, gpio.OUTPUT) -- trigger - GPIO15
   gpio.mode (7, gpio.INPUT)  -- echo    - GPIO13

   -- Halt, just in case...
   halt ( )
end

function loop ( )
   local distance = 0
   local command = 0
   local timestart = 0

   distance = read_usonic ( )
   -- Go forward until an object is 5cm or less
   if (distance > 5) then
      forward ( )
   else
      back_up ( )
      turn_left ( )
   end

   -- Do something to yield to the system a bit.
   tmr.wdclr ( )
   delay_ms (80)
end

function read_usonic ( )
   local pulse_start = 0
   local pulse_end = 0

   -- Send out the trigger signal to the sensor
   gpio.write (8, gpio.LOW);
   delay_us (5)
   gpio.write (8, gpio.HIGH);
   delay_us (10)
   gpio.write (8, gpio.LOW);

   -- Wait for echo to go HIGH
   while (gpio.read (7) == 0) do
      tmr.wdclr ( )
      pulse_start = tmr.now ( )
   end

   -- Wait for echo to drop LOW again
   while (gpio.read (7) == 1) do
      tmr.wdclr ( )
      pulse_end = tmr.now ( )
   end

   -- Return centimeters
   return ((pulse_end - pulse_start) / 58)
end

function back_up ( )
   --gpio.write (2, gpio.LOW);
   --gpio.write (3, gpio.HIGH);
   --gpio.write (1, gpio.LOW);
   --gpio.write (4, gpio.HIGH);

   set_pwm_on_pins (3, 4)
   pwm.setduty (3, 200)
   pwm.setduty (4, 200)

   delay_ms (500) -- Delay 500ms
   halt ( )
end

function turn_left ( )
   --gpio.write (2, gpio.LOW);
   --gpio.write (3, gpio.LOW);
   --gpio.write (1, gpio.HIGH);
   --gpio.write (4, gpio.LOW);

   set_pwm_on_pins (1, 4)
   pwm.setduty (1, 200)
   pwm.setduty (4, 200)

   delay_ms (500) -- Delay 500ms
   halt ( )
end

function forward ( )
   --gpio.write (2, gpio.HIGH);
   --gpio.write (3, gpio.LOW);
   --gpio.write (1, gpio.HIGH);
   --gpio.write (4, gpio.LOW);

   set_pwm_on_pins (1, 2)
   pwm.setduty (1, 400)
   pwm.setduty (2, 400)
end

function halt ( )
   pwm.stop (1)
   pwm.stop (2)
   pwm.stop (3)
   pwm.stop (4)
   pwm.close (1)
   pwm.close (2)
   pwm.close (3)
   pwm.close (4)
   --gpio.write (2, gpio.LOW);
   --gpio.write (3, gpio.LOW);
   --gpio.write (1, gpio.LOW);
   --gpio.write (4, gpio.LOW);
end

function delay_ms (milli_secs)
   local ms = milli_secs * 1000
   local timestart = tmr.now ( )

   while (tmr.now ( ) - timestart < ms) do
      tmr.wdclr ( )
   end
end

function delay_us (micro_secs)
   local timestart = tmr.now ( )

   while (tmr.now ( ) - timestart < micro_secs) do
      tmr.wdclr ( )
   end
end

function set_pwm_on_pins (pin1, pin2)
   -- Close off pwm on pins to free them up
   pwm.close (1)
   pwm.close (2)
   pwm.close (3)
   pwm.close (4)

   -- Set the pins sent in as pwm
   pwm.setup (pin1, 500, 512)
   pwm.setup (pin2, 500, 512)

   -- Start up the timer on pins
   pwm.start (pin1)
   pwm.start (pin2)
end

-- Function to test the delays with
function blink ( )
   gpio.write (2, gpio.LOW);
   print ("on")
   delay_ms (1000)

   gpio.write (2, gpio.HIGH);
   print ("off")
   delay_ms (1000)
end

-- Run the bot code
setup ( )
while (1) do
   loop ( )
end