Date: Wed, 24 Apr 2019 13:00:39 +0200 From: Emmanuel Vadot <manu@bidouilliste.com> To: Manuel =?ISO-8859-1?Q?St=FChn?= <freebsdnewbie@freenet.de> Cc: freebsd-arm@freebsd.org Subject: Re: I2C on Allwinner NanoPI Neo2 Message-ID: <20190424130039.2b425b0f3a2dda9affa41952@bidouilliste.com> In-Reply-To: <20190424122134.36e8dc112c62486d00703d4f@freenet.de> References: <20190424122134.36e8dc112c62486d00703d4f@freenet.de>
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Hi Manuel,
On Wed, 24 Apr 2019 12:21:34 +0200
Manuel St=FChn <freebsdnewbie@freenet.de> wrote:
> Hi,
>=20
> On my Allwinner NanoPI NEO2 (H5 aarch64 based) the I2C("allwinner,sun6i-a=
31-i2c" compatible, debug messages enabled) shows this message:
>=20
> root@bsd-nanopi:~ # i2c -v -f /dev/iic0 -a0x3c -d r -c 1
> dev: /dev/iic0, addr: 0x3c, r/w:twsi_locked_start(): no ACK (status: 08) =
after sending slave address r, offset: 0x00, width: 8, count: 1
> ioctl: error sending start condition
>=20
> while trying to communicate with the attached NanoHAT OLED (SSD1306 based=
I2C 0.96inch 128x64 display).
>=20
> Observing the bus with a logic analyzer shows, that between start conditi=
on and the address write there is a 10ms pause. Then the address gets writt=
en correctly and=20
> the device answers ACK. The I2C-clock is 100kHz which is confirmed by log=
ic analyzer.
>=20
> I'm assuming that this long delay between start condition and address wri=
te causes this error, but i do not find any problem in the i2c driver(iicbu=
s/twsi*). I've crosschecked the board with the default Linux image, and I2C=
works there without problems and there is no visible delay between start a=
nd addr-wr.
>=20
> Any ideas?
>=20
> --=20
> Manuel
i2c(8) uses the start/stop/read/write ioctls on the i2c device and
those don't use interrupts but a lots of DELAY calls. I've spent a few
hours trying to make things work without interrupts but gave up and
added i2c_transfer support to twsi that supports interrupts.
I guess that adding I2CRDWR (the ioctls that will call i2c_transfer)
to i2c(8) will not be that hard. So either do that or just code a
little program that suits your needs (see
https://lists.freebsd.org/pipermail/freebsd-arm/2019-April/019672.html
for more info on this).
Cheers,
--=20
Emmanuel Vadot <manu@bidouilliste.com> <manu@freebsd.org>
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