Date: Sat, 7 Dec 2024 23:53:04 +1030 From: Daniel O'Connor <darius@dons.net.au> To: =?utf-8?B?6aKo5L6G5pWj5Lq6?= <furaisanjin@gmail.com> Cc: FreeBSD ARM List <freebsd-arm@freebsd.org> Subject: Re: DS1307 on rpi4B Message-ID: <431FB386-F515-4D77-A855-18055A48E432@dons.net.au> In-Reply-To: <CAJzLSnxOALkCztZUa-zpUH30g1O0nUfQb4X2=4o_VDv3WTEdaQ@mail.gmail.com> References: <CAJzLSnxOALkCztZUa-zpUH30g1O0nUfQb4X2=4o_VDv3WTEdaQ@mail.gmail.com>
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> On 7 Dec 2024, at 20:26, =E9=A2=A8=E4=BE=86=E6=95=A3=E4=BA=BA = <furaisanjin@gmail.com> wrote: > I'm trying connect DS1307 on rpi4B (8M). I'm not sure how much I can = rely on the description in = https://github.com/raspberrypi/firmware/tree/master/boot/overlays = because I don't know the difference between linux boot loader and = FreeBSD one. >=20 > I want to connect DS1307 on GPIO12/13 pin as i2c5 so I assumed i2c-rtc = could be used so that I added one line in config.txt like below. >=20 > dtoverlay=3Di2c-rtc,ds1307,i2c5,addr=3D0x68 I have the following in /boot/msdos/overlays/pijuice.dtso (which needs = to be compiled to a dtbo): // Definition for RPi3 I2C based Real Time Clock /dts-v1/; /plugin/; / { compatible =3D "brcm,bcm2835"; fragment@0 { target =3D <&i2c1>; __overlay__ { #address-cells =3D <1>; #size-cells =3D <0>; status =3D "okay"; ds1307: ds1307@68 { compatible =3D "maxim,ds1307"; reg =3D <0x68>; status =3D "okay"; }; }; }; __overrides__ { ds1307 =3D <&ds1307>,"status"; }; }; And in /boot/msdos/config.txt: [all] ... # DS1307 RTC dtoverlay=3Dds1307 [pi4] gpio=3D2,3=3Da0 I got the last line from = https://lists.freebsd.org/pipermail/freebsd-arm/2021-May/023713.html After that=20 sudo i2c -f /dev/iic0 -m tr -s Shows the device. Also, be aware that currently the I2C frequency is quite a bit higher = than it should be when the CPU is clocked at the maximum as the divisors = are calculated based on the default clock. This doesn't seem to affect = the DS1307 even though it is only rated for 100kHz. -- Daniel O'Connor "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum
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