Date: Fri, 29 Aug 2014 15:07:17 -0300 From: Luiz Otavio O Souza <lists.br@gmail.com> To: Patrick Tracanelli <eksffa@freebsdbrasil.com.br> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, Rui Paulo <rpaulo@felyko.com> Subject: Re: HC-SR04 and FreeBSD Message-ID: <CAB=2f8w8vYr_zrN21nBhyR=Q4yUUw1Pa=_7zOZ3khS_NU9CEVQ@mail.gmail.com> In-Reply-To: <411C643B-BC46-494E-919B-39098FB87EEA@freebsdbrasil.com.br> References: <CAG4HiT6wwbmSA_KWsgHOqdeZVOCUsdhRxDhMubvkG1tEwVH5Sw@mail.gmail.com> <5D802942-2D0F-4324-8212-C2871EEB6327@FreeBSD.org> <CAG4HiT6fiqVXMoqcJra1Yh8aFVbOcezP8rRqst6WC8aHuaF_rA@mail.gmail.com> <01562FB1-32C6-45AF-AB77-5BB80526E18C@FreeBSD.org> <CAG4HiT4kKz18iauXfuF0Dpv-USghunssUvwkTF7bDx_gE_VS2w@mail.gmail.com> <CCD5AEE5-798D-4EAC-BAE7-A086DE55B5D2@FreeBSD.org> <CAG4HiT6YUBCxXrK_KyRW6zTthPa-wDe=A9=CmMHQf-Gh54s7QA@mail.gmail.com> <EA5A973C-960A-4B0F-A690-8AA9BF66244A@felyko.com> <CAG4HiT4EbX=Lar_o8YZc5B51Yao1-B=Ebck0vQajyzoZwesWwQ@mail.gmail.com> <CAB=2f8zBDTVkQd15C_icZpOMC14XxFycW_ZR2Sa--updv=dX2w@mail.gmail.com> <53F8FED8.6030409@freebsdbrasil.com.br> <CAG4HiT4RXsUyGfjDDTTJPoeB8bqpY39z6C-_f0S3Zmka0C8gNQ@mail.gmail.com> <3949AF9C-B5BD-44E8-A049-21F26B8B6B9A@freebsdbrasil.com.br> <CAB=2f8xyu1EwL3zft8E%2BSXRL66vdYSjgcSuhF7Kva9zDatGtXA@mail.gmail.com> <411C643B-BC46-494E-919B-39098FB87EEA@freebsdbrasil.com.br>
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Okay, so i got my hands on one HC-SR04 and got it working quite easily. Two consecutive GPIO readings takes from 15 to 30 usec which gives a good precision for this case (readings above 116 usec). I written a simple C program to program the GPIO pins, trigger the sensor and read back the duration of echo pulse, it give me good readings using the datasheet formula, so i'm happy with it. Build it with: cc -o hc-sr04 hc-sr04.c I'm using the wiring suggested at (voltage divisor on echo pin): https://www.modmypi.com/blog/hc-sr04-ultrasonic-range-sensor-on-the-raspberry-pi The trigger and echo pin is connected to pins 2 and 3 respectively. The module is powered from DGND and VDD_5V. This maybe a good candidate to be on Wiki. Luiz
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