Ultrasonic sensor driver for the esp8266
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README.md

esp8266_ping

A HC-SR04, HY-SRF05 driver and example for the esp8266.

#include "ping/ping.h"
....
static Ping_Data pingA;
....
// setup
int triggerPin = 0;
int echoPin = 2;
ping_init(&pingA, triggerPin, echoPin, PING_MM); // set the trigger and echo pin to the same number for one-pin mode

....
// loop:
float distance = 0;
float maxDistance = 500;
if (ping_pingDistance(&pingA, maxDistance, &distance) ) {
  os_printf("Response ~ %d mm \n", (int)distance);
} else {
  os_printf("Failed to get any response.\n");
}

Makefile:

MODULES         = driver/stdout driver/easygpio driver/ping user

##Circuit The HC-SR04 is a 5V device, so you will (at the very least) need a voltage divider on the echo pin. Or even better: a logic level shifter.

Two pins

single pin mode

Single pin mode - level shifter

If you want to run this in 'single pin mode' behind a logic level shifter you can connect the echo pin on the 3V3 side to the trigger GPIO via a 4KΩ:ish resistor. This works for a a classic MOSFET level shifter built out of two BSS138 and four 10KΩ resistors. Make sure that the esp GPIO reads low (input mode) when HC-SR04 echo pin is driven low. If it reads high the R2 resistor needs lower resistance.

Wiring echo & trigger together on the 5V side does not work with a classic mosfet level shifter.

Single pin mode - voltage divider

Another working solution is a voltage divider (5V to 3.3V) between HC-SR04 echo and ground. Connect HC-SR04 trigger and esp GPIO to the middle of the divider.

other sensors

The arduino library newping supports a whole range of ultrasonic sensors: SR04, SRF05, SRF06, DYP-ME007 & Parallax PING™. This without making any special hardware considerations in the code. So this library should work with those sensors as well.

TODO

  • inches
  • single pin mode
  • multiple sensors
  • sdk v0.9.5 compability
  • check compability SRF05 SRF05 works w/o any modifications
  • check compability SRF06
  • check compability DYP-ME007
  • check compability Parallax PING™

License

GPL V3

The makefile is copied from esp_mqtt.

###Building and installing:

First you need to install the sdk and the easy way of doing that is to use esp_open_sdk.

You can put that anywhere you like (/opt/local/esp-open-sdk, /esptools etc etc)

Then you could create a small setenv.sh file, containing the location of your newly compiled sdk and other platform specific info;

export SDK_BASE=/opt/local/esp-open-sdk/sdk
export PATH=${SDK_BASE}/../xtensa-lx106-elf/bin:${PATH}
export ESPPORT=/dev/ttyO0  

(or setup your IDE to do the same)

To make a clean build, flash and connect to the esp console you just do this in a shell:

source setenv.sh # This is only needed once per session
make clean && make test

You won't be needing esptool, the makefile only uses esptool.py (provided by esp_open_sdk)

I have tested this with sdk v1.5.2, v0.9.4 and v0.9.5 (linux & mac)