Date: Mon, 11 Jul 2022 00:18:59 -0300 From: "Dr. Rolf Jansen" <freebsd-rj@cyclaero.com> To: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: i2c bus via USB adapter Message-ID: <FADF0E7F-BB60-4A4A-B227-87CA912841AE@cyclaero.com> In-Reply-To: <YsuIZS0/IrLjsVvR@phouka1.phouka.net> References: <YsuIZS0/IrLjsVvR@phouka1.phouka.net>
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> Am 10.07.2022 um 23:18 schrieb John Kennedy <warlock@phouka.net>: >=20 > Along with trying to attach some I2C devices to my RPI4 (which has > GPIO-pin exposure issues due to heatsink-case), I tried attaching this > device from Adafruit: >=20 > Adafruit MCP2221A Breakout - General Purpose USB to GPIO ADC I2C = Stemma QT / Qwiic > https://www.adafruit.com/product/4471 I cannot help you with this piece. However, did you know that we can easily enable just some more I2C = busses of the RPi4 using other pins on the header. For example I enabled = I2C5 running on GPIO12/13. This works concurrently to the default I2C1 = on GPIO2/3. The respective numbers of the physical pins on the header for I2C5 are: 17: 3.3 V 32: SDA 33: SCL 34: GND These pins are on the other end to where you connected the vent of the = heat sink, and chances are that these are still accessible. Anyway, for enabling I2C5 (we may choose from I2C3, I2C4, I2C5 and I2C6) = on a Raspberry Pi 4, we do: # fetch = https://github.com/raspberrypi/linux/blob/rpi-5.15.y/arch/arm/boot/dts/ove= rlays/i2c5-overlay.dts # dtc -I dts -O dtb -b0 -@ -o /boot/msdos/overlays/i2c5.dtbo = i2c5-overlay.dts Then we add the following 2 lines to /boot/msdos/config.txt: gpio=3D12,13=3Da5 dtoverlay=3Di2c5,pins_12_13 While my DS3231 RTC breakout board worked on these pins (phys. #32,#33) = without any problem, I needed to add 3.3 k=CE=A9 pull-up resistors to = the SDA and SCL lines for other modules. Most probably said RTC breakout = came already with pull-ups on board. Anyway, finally I left the RTC on = the default I2C bus. In dmesg: ... iicbus0: <OFW I2C bus> on iichb0 iic0: <I2C generic I/O> on iicbus0 ds32310: <Maxim DS3231 RTC> at addr 0xd0 on iicbus0 iicbus1: <OFW I2C bus> on iichb1 iic1: <I2C generic I/O> on iicbus1 ...=
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