.. | ||
application.fam | ||
dist_sensor10px.png | ||
hc_sr04.c | ||
README.md |
HC_SR04
Description
The original version is from SquachWare hc_sr04.
This version modifies the code to use furi_hal_cortex_timer_get(0) to obtain a high precision counter. We also tune the calculations based on measured observations. The display shows 2 digits after the decimal point, displaying in both cm and inches.
Pins
- (Flipper -> HC_SR04 device)
- (5V -> VCC)
- (GND -> GND)
- (13|TX -> Trig)
- (14|RX -> Echo)
Code changes
- #include <furi_hal_cortex.h>
- This has the definitions for FuriHalCortexTimer and furi_hal_cortex_timer_get(...)
- FuriHalCortexTimer beginTimer = furi_hal_cortex_timer_get(0);
- This gets the current time in beginTimer.start.
- The offset is 0 (we could use offset ).
- furi_string_printf(str_buf, "Distance: %0.2f cm", (double)plugin_state->distance);
- This rounds the output to the nearest hundredths place.
- hc_sr04_duration_to_cm(...)
- I have no idea why total_dist needs to be multiplied by 1.588, but doing so seems to make all of the measurements correct.
- The code overhead, delays in IN/OUT, etc. seem to take the same time as sound tranvelling for 0.497 cm there and back; so we add this fixed constant. If you Flipper was faster/slower you would need to adjust this constant.