From: Yasushi SHOJI <yasushi.shoji@gmail.com>
To: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: "Marc Kleine-Budde" <mkl@pengutronix.de>,
"Remigiusz Kołłątaj" <remigiusz.kollataj@mobica.com>,
"Yasushi SHOJI" <yashi@spacecubics.com>,
"Wolfgang Grandegger" <wg@grandegger.com>,
linux-can@vger.kernel.org
Subject: Re: [PATCH] can: mcba_usb: Fix termination command argument
Date: Thu, 24 Nov 2022 22:13:03 +0900 [thread overview]
Message-ID: <CAELBRWKz57boSG1B=ONQ1Ax2TXw9FTHj36aG6p0VKp_tyHx2mg@mail.gmail.com> (raw)
In-Reply-To: <5a309931-ca81-5433-b437-5c8ec23c4d85@hartkopp.net>
Hi again,
On Thu, Nov 24, 2022 at 7:09 PM Oliver Hartkopp <socketcan@hartkopp.net> wrote:
> I assumed "termination 0" results in "termination off" (=> no
> termination => very high resistor value) but in fact it gets around 20
> Ohms, which is a pretty heavy termination for a CAN bus.
I've checked with one of my colleagues and he told me I measured it wrong.
Here is a correction.
You can find the schematic of the analyzer in its user's guide
https://www.microchip.com/en-us/development-tool/APGDT002
or directly at https://ww1.microchip.com/downloads/aemDocuments/documents/APG/ProductDocuments/UserGuides/CAN-Bus-Analyzer-Users-Guide-DS50001848C.pdf
The schematics is at page 11.
Basically the "termination" controls the CAN_RES signal. When it's
low, R24 and R25 are connected to the bus.
They are 56 Ohms.
With my patch, "termination 120" drives CAN_RES low and the resistors
are active, and "termination 0" drives it high.
--
yashi
next prev parent reply other threads:[~2022-11-24 13:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-23 19:44 [PATCH] can: mcba_usb: Fix termination command argument Yasushi SHOJI
2022-11-23 22:34 ` Marc Kleine-Budde
2022-11-24 9:50 ` Yasushi SHOJI
2022-11-24 10:09 ` Oliver Hartkopp
2022-11-24 12:32 ` Yasushi SHOJI
2022-11-24 13:13 ` Yasushi SHOJI [this message]
2022-11-24 20:15 ` Oliver Hartkopp
2022-11-24 0:53 ` Vincent Mailhol
2022-11-24 9:52 ` Yasushi SHOJI
2022-11-24 9:54 ` Vincent Mailhol
2022-11-24 14:38 ` Marc Kleine-Budde
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