iic

[Oskar Holmlund]

Hi Elwood,


2021-02-13 03:02 skrev Elwood Downey:
> Hello all!
> 
> Trying IIC on RPi 4b 4GB, no joy yet. Looking for ideas. So far:
> 
>    - bus seems to be present based on dmesg and /dev/iic0 (see below)
>    - device is BME280 <https://www.adafruit.com/product/2652> env 
> sensor at
>    IIC address 0x77.
>    - wiki page here <https://wiki.freebsd.org/arm/Raspberry%20Pi> 
> suggests
>    it should work.
>    - The table says "OK (brcm BSC)" but not sure what that extra bit 
> means.
>    - Tried all the kernels mentioned on that page with no luck so 
> decided
>    on some 13-BETAs, still no luck.
>    - Device is known to work on the same hardware running Raspbian 10
>    "buster".
>    - tried the I2CRDWR-only test program here
> 
> <https://vzaigrin.wordpress.com/2014/04/28/working-with-i2c-in-freebsd-on-raspberry-pi/>
>    but that does not find my device either
> 
> Suggestions welcome!
> 
> adTHANKSvance
> 
> Elwood Downey
> Tucson AZ
> 
> 
> freebsd at generic:~ % dmesg | grep iic
> 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
> 
> freebsd at generic:~ % uname -a
> FreeBSD generic 13.0-BETA2 FreeBSD 13.0-BETA2 #0
> releng/13.0-n244498-6461715f1ae: Fri Feb 12 06:21:00 UTC 2021
> root at releng1.nyi.freebsd.org:/usr/obj/usr/src/arm64.aarch64/sys/GENERIC
>  arm64
> 
> freebsd at generic:~ % ls -l /dev/iic0
> crw-------  1 root  wheel  0x45 Feb 12 07:01 /dev/iic0
> 
> freebsd at generic:~ % sudo i2c -s
> Hardware may not support START/STOP scanning; trying less-reliable read
> method.
> Scanning I2C devices on /dev/iic0: <none found>
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- device is BME280 <https://www.adafruit.com/product/2652> env sensor at
   IIC address 0x77.

Are you using the "STEMMA QT" interface or have you done the wiring?
If you did the wiring, how?

I dont have any RPI to try myself. But i do have an pocketbeagle with a 
mikroe weather click:
https://www.mikroe.com/weather-click

# i2c -s -f /dev/iic1
Hardware may not support START/STOP scanning; trying less-reliable read 
method.
Scanning I2C devices on /dev/iic1: 76

In my case I need to apply an device tree overlay[1] to get the i2c1 to 
work, not sure if its needed for RPI.
You may check your running devicetree: # sysctl -b hw.fdt.dtb | dtc -I 
dtb -O dts > running.dts

I have written a driver for bme280 that I can share after cleaning up.


[1] devicetree overlay for AM3358 (Pocketbeagle, Beagleboneblack:ish 
...)
https://github.com/RobertCNelson/bb.org-overlays/blob/master/src/arm/PB-I2C1-WEATHER-CLICK.dts

With modifications:
/*
  * Copyright (C) 2017 Robert Nelson <robertcnelson at gmail.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
/dts-v1/;
/plugin/;

#include <dt-bindings/board/am335x-bbw-bbb-base.h>
#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/pinctrl/am33xx.h>

/ {
         fragment at 0 {
                 target = <&am33xx_pinmux>;
                 __overlay__ {
                         pb_tl_i2c1_pins: pinmux_pb_tl_i2c1_pins {
                                 pinctrl-single,pins = <
                                         /* (D15) uart1_txd.i2c1_scl */
                                         AM33XX_IOPAD(0x0984, 
PIN_OUTPUT_PULLUP | INPUT_EN | MUX_MODE3)
                                         /* (D16) uart1_rxd.i2c1_sda */
                                         AM33XX_IOPAD(0x0980, 
PIN_OUTPUT_PULLUP | INPUT_EN | MUX_MODE3)
                                 >;
                         };
                 };
         };
         fragment at 1 {
                 target = <&i2c1>;
                 __overlay__ {
                         status = "okay";

                         #address-cells = <1>;
                         #size-cells = <0>;

                         pinctrl-names = "default";
                         pinctrl-0 = <&pb_tl_i2c1_pins>;

                         bmp280 at 76 {
                                 compatible = "bosch,bme280";
                                 reg = <0x76>;
                                 bme280,humidity_oversampling=<1>;
                                 bme280,temperature_oversampling=<1>;
                                 bme280,pressure_oversampling=<1>;
                                 bme280,filter=<0>;
                                 bme280,Tstandby=<0>;
                         };
                 };
         };
};


-- 
Bästa Hälsningar
Oskar Holmlund
Tel 070-3220292