From: Bob Goddard <1963bib@googlemail.com>
Subject: Re: GNATCOLL-Mmap example
Date: Wed, 29 Jan 2020 13:56:56 -0800 (PST)
Date: 2020-01-29T13:56:56-08:00 [thread overview]
Message-ID: <bcabe239-c048-417b-a435-adb54d377e20@googlegroups.com> (raw)
In-Reply-To: <r0rf5s$17fb$1@gioia.aioe.org>
On Wednesday, 29 January 2020 08:19:11 UTC, Dmitry A. Kazakov wrote:
[...]
> >>> This was the way I started, but could not get it to read anything. It just blocks trying to read a single character. My c code works fine using the wiringPi libs.
> >>
> >> If I correctly remember you should rewind the file after each reading.
> >
> > It did not get that far. It blocks right at the start.
>
> What about this
>
> use GNAT.OS_Lib;
>
> FD : File_Descriptor;
> Buffer : aliased char;
> begin
> FD := Open_Read ("/sys/class/gpio/gpio/XXX/value", Binary);
> Lseek (FD, 0, Seek_Set);
> if 1 = Read (FD, Buffer'Address, 1) then
> if Buffer = '1' then
> ...
Well... the call does not block, but I get spurious info back. It fires 1000 in around 1/4s, when it should be about 50Hz, that being the mains line frequency here.
On read, it should be reset. I tried making it RW, but the write fails.
Ho hum, that dent in the wall is getting bigger.
B
next prev parent reply other threads:[~2020-01-29 21:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-25 21:52 GNATCOLL-Mmap example Bob Goddard
2020-01-28 2:10 ` Stephen Leake
2020-01-28 5:59 ` J-P. Rosen
2020-01-28 8:25 ` Dmitry A. Kazakov
2020-01-28 18:53 ` Bob Goddard
2020-01-28 20:07 ` Dmitry A. Kazakov
2020-01-28 20:17 ` Bob Goddard
2020-01-29 8:19 ` Dmitry A. Kazakov
2020-01-29 21:56 ` Bob Goddard [this message]
2020-01-30 2:45 ` Dennis Lee Bieber
2020-01-31 16:59 ` Björn Lundin
2020-01-28 19:11 ` Philip Munts
2020-01-28 20:15 ` Dmitry A. Kazakov
2020-01-28 20:18 ` Philip Munts
2020-01-28 22:06 ` Bob Goddard
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