HC-SR04 and FreeBSD

Evandro Nunes evandronunes12 at gmail.com
Thu Aug 21 18:44:38 UTC 2014


On Thu, Aug 21, 2014 at 1:24 PM, Rui Paulo <rpaulo at freebsd.org> wrote:

> On Aug 20, 2014, at 22:34, Evandro Nunes <evandronunes12 at gmail.com> wrote:
>
> > On Thu, Aug 21, 2014 at 2:05 AM, Rui Paulo <rpaulo at freebsd.org> wrote:
> > On Aug 20, 2014, at 21:52, Evandro Nunes <evandronunes12 at gmail.com>
> wrote:
> >
> > > On Thu, Aug 21, 2014 at 1:51 AM, Rui Paulo <rpaulo at freebsd.org> wrote:
> > > On Aug 20, 2014, at 21:48, Evandro Nunes <evandronunes12 at gmail.com>
> wrote:
> > >
> > > > hello,
> > > >
> > > > ive got a ultrasonic sensor model HC-SR04 and a beaglebone black as
> well as
> > > > a cubieboard2, both running FreeBSD 11 built from crochet and wiki
> > > > instructions
> > > >
> > > > thanks to the help from loos@ I could manage to use a 5v relay with
> BBB
> > > > now, how can I read data from HC-SR04 sensor? do we have any library
> > > > available? or do we have any GPIO utility to do that?
> > > > btw how can I read values from GPIO pins when they are set to input?
> > >
> > > I wrote a library to handle GPIO on FreeBSD:
> > >
> > >         https://bitbucket.org/rpaulo/libgpio
> > >
> > > very good :-) I will play with that
> > >
> > > You can also use the gpioctl utility in FreeBSD to read values.
> > >
> > > how? can you point me to any further reading, blog entry, or examples?
> >
> > There's a man page, but "gpioctl -c <PIN> IN" will set the pin in input
> mode.  Then, "gpioctl <PIN>" will read the value.
> >
> > so this way I should read something from HC-SR04 echo pin on BBB?
> > I am using another gpio pin in output mode as a trigger, according to
> what I've read, 3.3v is OK as a trigger for this sonar
> >
> > but when I read the GPIO pin in input mode just as you mentioned, I
> always get a 0 value...
> > I am using BBB's P9_1 and P9_5 for +5v and ground, P9_21 as a trigger
> and P9_23 as echo; set GPIO 3 (P9_21) as output and GPIO 49 (P9_23) as input
> > I made a loop to read GPIO 49 every 100ms and another loop to trigger
> (gpioctl -t 3; sleep .100; gpioctl -t 3) every 2 seconds.
> >
> > what I am doing wrong? feeding 3.3v for 0.1 seconds as a trigger
> should't cause something to echo?
>
> Don't you have a multimeter?  Have you measured the voltage on the output
> pin when you switch it to 0 and then back to 1?
>

no, I don't have a working multimeter, mine is dead. I will buy another one
and test it as suggested, yes you are right, although I dont have an idea
on what value it should be expected

but for curiosity, will gpioctl 49 show values anyhow equivalent to what a
multimeter would display? or I should not expect anything similar?
sorry for that question if this is too dummy, yes I completely lack on GPIO
basics, it's my first experience rss





> --
> Rui Paulo
>
>
>
>


More information about the freebsd-arm mailing list