From: Antony Pavlov <antonynpavlov@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [RFC 0/2] sandbox: add gpio support with libftdi1
Date: Thu, 16 Feb 2017 11:28:35 +0300 [thread overview]
Message-ID: <20170216112835.e13918c2dc0499e64e1366a2@gmail.com> (raw)
In-Reply-To: <20170216073430.4hctt6wnbkfiemtk@pengutronix.de>
On Thu, 16 Feb 2017 08:34:30 +0100
Sascha Hauer <s.hauer@pengutronix.de> wrote:
> Hi Antony,
>
> On Wed, Feb 15, 2017 at 10:12:25AM +0300, Antony Pavlov wrote:
> > This patch series makes it possible to use FT2232H ACBUS[7:0]
> > pins as gpio pins from sandbox barebox.
> >
> > I have tested output gpio functionality by connecting
> > a LED to ACBUS[0] and lightening it with gpio_direction_output
> > and gpio_set_value barebox commands.
> >
> > Also I have performed input test with ACBUS[0] -> ACBUS[1] loopback.
> >
> > The main goal of adding gpio functionality to sandbox barebox
> > is using it for connecting real i2c and spi devices to sandbox barebox
> > (not tested yet).
>
> I just read that the FT2232H can even do native I2C and SPI, so no gpio
> bitbanging would be necessary.
I suppose that gpio support itself is valuable.
> Would it be possible to use this mode instead?
Yes, FT2232H has MPSSE acellerator.
Using MPSSE one can increase FT2232 I2C/SPI performance dramatically.
I have compared two FT2232 I2C realizations (bitbang and libmpsse,
see https://github.com/frantony/mprog/tree/master/i2c_access).
on reading of 8 KiB data block from I2C eeprom. libmpsse's bandwidth is 6 KiB per second,
bitbang's bandwidth is only 73 bytes per second (nearly 100 times worse).
Alas, I have no time to realize ftdi fast i2c/spi support for barebox in the nearest future
> Otherwise I think there should be a possibility to specify which, if
> any, FT2232H chip barebox uses.
I'll add cmdline options to select FT2232H chips on USB bus in v2 patchseries.
Also I'll check i2c bitbang support. I can connect ds1307 rtc or at24 eeprom).
--
Best regards,
Antony Pavlov
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next prev parent reply other threads:[~2017-02-16 8:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-15 7:12 Antony Pavlov
2017-02-15 7:12 ` [RFC 1/2] sandbox: avoid symbol conflict for {open,read,close}dir Antony Pavlov
2017-02-15 7:12 ` [RFC 2/2] sandbox: add gpio support with libftdi1 Antony Pavlov
2017-02-16 7:34 ` [RFC 0/2] " Sascha Hauer
2017-02-16 8:28 ` Antony Pavlov [this message]
2017-02-16 8:25 ` Sascha Hauer
2017-02-16 11:11 ` Ian Abbott
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