ESP8266 Community Forum

- Tue Nov 08, 2016 3:34 pm #57846 Hello everyone!
I am using hcsr04 ultrasonic sensor to measure distance. While the NodeMCU is running the official firmware from Github, the sensor works fine. However, when the NodeMCU is flashed with customized firmware from https://nodemcu-build.com/, then the sensor does not work. I used the same code for both. I am sure I have selected all the necessary modules. I have no idea what the problem is. Code is attached below. Thanks for your help!

Code: Select alltime_start = 0
time_end = 0
trig = 8
echo = 7
gpio.mode(trig, gpio.OUTPUT)
gpio.mode(echo, gpio.INT)

function echo_cb(level)
    if level == 1 then
        time_start = tmr.now()
        gpio.trig(echo, "down", echo_cb)
    else
        time_end = tmr.now()
    end
end

function measure()
    gpio.trig(echo, "up", echo_cb) -- Echo pin at rising edge, call echo_cb
    gpio.write(trig, gpio.HIGH) -- trig low
    tmr.delay(100)
    gpio.write(trig, gpio.LOW) -- trig high
    tmr.delay(100000) -- delay 10ms
    if (time_end - time_start) < 0 then
        return -1
    end
    return (time_end - time_start) / 58
end

distance = measure()
print("Distance: " .. distance .. " cm")


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