Re: I2C/IIC working on RPI4 8GB?

Mark Murray <[email protected]> Wed, 28 Apr 2021 09:01:56 +0100

Newsgroups	gmane.os.freebsd.devel.arm
Message-ID	<[email protected]>

On 27 Apr 2021, at 21:13, Mark Millard <[email protected]> wrote:
> 
> Did you try the suggestion in:
> 
> https://lists.freebsd.org/pipermail/freebsd-arm/2021-April/023687.html
> 
> ? It suggests that you need to have the config.txt swap
> the the pins in order to undo another swap that happens
> at some internal stage. The swapped problem was indicated
> to be visible in the dmesg reporting and the manual swap
> was reported to cause the dmesg reporting to produce the
> correct overall result.

I took apart the i2c1.dtbo overlay that mentions pins 2, 3, and swapped them, and reassembled the overlay.

Nope. Same problem.

What I have:

[root@grasshopper ~]# dmesg | egrep -i 'ds3231|rtc|i2c|iic|time-of-day'
iichb0: <BCM2708/2835 BSC controller> mem 0x7e804000-0x7e804fff irq 26 on simplebus0
iicbus0: <OFW I2C bus> on iichb0
iic0: <I2C generic I/O> on iicbus0
Warning: no time-of-day clock registered, system time will not be set accurately

[root@grasshopper ~]# ls -al /dev | grep iic
crw-------   1 root  wheel     0x44 Apr 28 08:42 iic0

I have found a PDF document "BCM2711 ARM Peripherals", and it says "The BSC controller in the BCM2711 fixes the clock-strectching[sic] bug that was present in BCM283x devices", so I suspect that the device may not be hardware compatible with the RPI3 and earlier.

Time to dig in and hack.

M
--
Mark R V Murray

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