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Subject: Re: DS1307 on rpi4B
From: Daniel O'Connor <darius@dons.net.au>
In-Reply-To: <CAJzLSnyf0z=TOOaQyCuobfhhHT8F+px=VbqqEooiP+cs+BQ2Qw@mail.gmail.com>
Date: Sun, 8 Dec 2024 14:59:17 +1030
Cc: FreeBSD ARM List <freebsd-arm@freebsd.org>
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To: =?utf-8?B?6aKo5L6G5pWj5Lq6?= <furaisanjin@gmail.com>
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> On 8 Dec 2024, at 14:42, =E9=A2=A8=E4=BE=86=E6=95=A3=E4=BA=BA =
<furaisanjin@gmail.com> wrote:
> I'm using this module =
(https://www.electronicwings.com/sensors-modules/real-time-clock-rtc-ds130=
7-module) and there are R2 and R3 for pull-up on the module. The =
registers are connected to 5V. This probably harms RPI4B because the =
voltage is 3.3V at RPI4B side. So I removed R2 and R3. That's why =
internal pull-up is required.

Ah that is unfortunate.

There is 3.3V on the 40 pin RPi header you could connect to R2/R3 (and =
cut the connection to 5V obviously).

--
Daniel O'Connor
"The nice thing about standards is that there
are so many of them to choose from."
-- Andrew Tanenbaum