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William Leue
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Joined: 03/07/2020
Location: United States
Posts: 405

Posted: 08:10pm 03 Sep 2020

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I have been working on building an adaptor box for supporting additional Nunchuks using the I2C pins available at the rear 40-pin data connector on the CMM2.

Most of the connections are obvious but I do have a couple of concerns.

According to online sources, the Nintendo connector has 6 traces, one of which is not used:

Pin Use
--- -----------------
1 +3.3v VCC
2 Ground
3 Data
4 No connection
5 Feeds 3.3v back for detection
6 Clock

So, looking at the pinout table in the CMM2 documentation, it seems clear that the following connections make sense:

CMM2 Pin Nunchuk #1 NunChuk#2 Use
-------- ---------- --------- ------------
1 1 +3.3v VCC
3 3 I2C 1 Data
5 6 I2C 1 Clock
7 5?? detect Nunchuk?
9 2 Ground
17 1 +3.3v VCC
25 2 Ground
27 3 I2C 2 Data
28 6 I2C 2 Clock
29?? 5?? detect Nunchuk?

The only two pins I am uncertain about are the two pins used by the Nunchuk to feed back 3.3v power so that the box can detect when the Nunchuk is connected. Any I/O pin could be used for this, but which ones are actually used by the CMM2 firmware?

-Bill

William Leue
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Joined: 03/07/2020
Location: United States
Posts: 405

Posted: 08:12pm 03 Sep 2020

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Well, I forgot to switch to a monospaced font for the table so it looks ugly. Let me try again:

CMM2 Pin Nunchuk #1 NunChuk#2 Use
-------- ---------- --------- ------------
1 1 +3.3v VCC
3 3 I2C 1 Data
5 6 I2C 1 Clock
7 5?? detect Nunchuk?
9 2 Ground
17 1 +3.3v VCC
25 2 Ground
27 3 I2C 2 Data
28 6 I2C 2 Clock
29?? 5?? detect Nunchuk?

-Bill

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6283

Posted: 09:35pm 03 Sep 2020

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You should be able to forget about the "detect nunchuk" pin.
MMBasic doesn't use it.
You could tie it to the 3.3V pin just in case your nunchuk uses that pin for power.

Jim

VK7JH
MMedit

vegipete

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Joined: 29/01/2013
Location: Canada
Posts: 1132

Posted: 11:15pm 03 Sep 2020

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The nunchuk port on the front doesn't use the detect pin so if your device works there, you won't need it for ports 1 or 2. But as Jim says, if you are making a pcb, add 2 pads that you can jumper if needed.

Visit Vegipete's *Mite Library for cool programs.

William Leue
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Joined: 03/07/2020
Location: United States
Posts: 405

Posted: 12:03pm 04 Sep 2020

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Hmm. If I try to use the nunchuk commands without a nunchuk plugged in, CMM2 tells me that no nunchuk is connected. So if it does not use the 'detect' pins, how does it know?

-Bill

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10310

Posted: 12:09pm 04 Sep 2020

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Quote how does it know?

Looks for a valid I2C response

Quazee137

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Joined: 07/08/2016
Location: United States
Posts: 593

Posted: 08:00pm 04 Sep 2020

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William Leue have a look here

back of CMM2

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