I2C/IIC working on RPI4 8GB?

Thu Apr 29 18:17:09 UTC 2021

On 2021-Apr-29, at 09:57, Mark Murray <markm at freebsd.org> wrote:

> On 28 Apr 2021, at 22:07, Mark Murray <markm at FreeBSD.org> wrote:
>> 
>> On 28 Apr 2021, at 09:19, Emmanuel Vadot <manu at bidouilliste.com> wrote:
>> 
>>> According to this document is this just to detect that the slave hold
>>> the scl line too long so I don't think that this is the problem here.
>>> If you have a scope or a logic analyzer I suggest you start by using
>>> it to confirm that when you scan with i2c -s you see something.
>> 
>> As it turns out, my logic analyser arrived today.
> 
> I got an oscilloscope onto pins 3 and 5 (GPIO2 and GPIO3), and "i2c -s" does not a jot on them.
> 
> I don't know if this helps, but the gpioctl utility thinks the pins are both inputs:

Looking around, I see:

https://github.com/raspberrypi/hats/blob/master/designguide.md

says:

QUOTE
The default state for all Bank 0 pins will be inputs with either a pull up or pull down. The default pull state can be found in the BCM2835 peripherals specificaion section 6.2 table 6-31 (see the "Pull" column). It will require positive software configuration to change the state of these pins.

The one exception to this rule is ID_SC and ID_SD. GPIO0 (ID_SD) and GPIO1 (ID_SC) will be switched to ALT0 (I2C-0) mode and probed for an EEPROM at boot time. These pins will revert to inputs once the probe sequence has completed.
END QUOTE

https://github.com/raspberrypi/hats has some other documents
as well.

If this note is redundant for you, sorry.

> [root at grasshopper ~]# gpioctl -f /dev/gpioc0 -l -v
> pin 00:	1	pin 0<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 01:	1	pin 1<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 02:	1	pin 2<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 03:	1	pin 3<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 04:	1	pin 4<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 05:	1	pin 5<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 06:	1	pin 6<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 07:	0	pin 7<OUT>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 08:	0	pin 8<OUT>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 09:	0	pin 9<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 10:	0	pin 10<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 11:	0	pin 11<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 12:	0	pin 12<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 13:	0	pin 13<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 14:	1	pin 14<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 15:	1	pin 15<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 16:	0	pin 16<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 17:	0	pin 17<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 18:	0	pin 18<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 19:	0	pin 19<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 20:	0	pin 20<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 21:	0	pin 21<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 22:	0	pin 22<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 23:	0	pin 23<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 24:	0	pin 24<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 25:	0	pin 25<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 26:	0	pin 26<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 27:	0	pin 27<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 28:	1	pin 28<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 29:	0	pin 29<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 30:	1	pin 30<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 31:	1	pin 31<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 32:	0	pin 32<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 33:	0	pin 33<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 34:	1	pin 34<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 35:	1	pin 35<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 36:	1	pin 36<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 37:	1	pin 37<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 38:	1	pin 38<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 39:	1	pin 39<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 40:	0	pin 40<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 41:	0	pin 41<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 42:	0	pin 42<OUT>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 43:	1	pin 43<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 44:	1	pin 44<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 45:	1	pin 45<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 46:	0	pin 46<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 47:	0	pin 47<IN>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 48:	0	pin 48<>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 49:	0	pin 49<PU>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 50:	0	pin 50<PU>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 51:	0	pin 51<PU>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 52:	0	pin 52<PU>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>
> pin 53:	0	pin 53<PU>, caps:<IN,OUT,PU,PD,INTRLL,INTRLH,INTRER,INTREF,INTREB>

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)