sza2
Incorrect reading?
I used your code but I only get incorrect readings from the HC-SR04 sensor.
I did some debug modifications in the function self.measure() see below:
function self.measure() gpio.trig(self.echo, "up", self.echo_cb) gpio.write(self.trig, gpio.HIGH) tmr.delay(100) gpio.write(self.trig, gpio.LOW) tmr.delay(100000) if (self.time_end - self.time_start) < 0 then return -1 end -- Modified for debug purpose print ("-------------------") print (self.time_start) print (self.time_end) print (self.time_end - self.time_start) print ("-------------------") return (self.time_end - self.time_start) / 58
This is the debug printout of the self.time_start and _end
1079788923 1079789402
479
1079897355 1079897818
463
1080035710 1080036173
463
1080174067 1080174530
463
7
1080788919 1080789402
483
1080897355 1080897822
467
1081035711 1081036177
466
1081174065 1081174532
467
8
Do you have an explination to why the time between trigger and echo is constant at around 460-470 us even if there is nothing infront of the sensor.
Could you also explain why you devide the delta time by 5800, I am guessing it has something to do with the speed of sound in air. 343 m/s = 34300 cm/s
What am i doing wrong? ;) Thanx for your support
