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panky

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Joined: 02/10/2012
Location: Australia
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Posted: 07:33pm 23 Nov 2016

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Interesting (and frustrating problem).

Built the Silicon Chip Backpack Plus board in the Nov 16 issue. Assembled and configured as per Sil Chip article and all came up OK and runs programs fine under MMBasic 5.2

However, when attaching the Sil Chip supplied 2.8" LCD, no display, no touch and no sd card operations.

Ran the display on a CG Microboard 2 - works fine for display, touch and sd card;
Ran the display on a P Mather board - works fine as above;
Tried an alternate 2.4 display on the Sil Chip board - no go!
(2.4 display works fine on CG Microboard 2 and P Mather board)

Re loaded MMBasic 5.2 with PicKit 3 - problem same as before.

Removed LCD display from backpack and used backpack sd card - works fine;

Option disabled LCD, touch and SD card functionality - set PWM2B (pin 47, same pin as used as SPI2 In) to pulse - works fine;

With LCD, touch and sdcard enabled correctly, oscilloscope shows correct signals on all lines EXCEPT the SPI2 In (pin 47). It sits at around 1Volt with 300 to 400mV pulses on it when doing the GUI TEST LCDPANEL command.

Same action on the CG Microboard2 with the 2.8" display gives a correct 3.3V pulse train.

When LCD disconnected and disabled, using on board SD card, pulse train on pin47 (SPI2 In) is also correct at 3.3V

So, SPI2 In MUST be working as the on board SD Card works;
The LCD display MUST be working as it works fully on other platforms;
Pin 47 and thus the PIC32MX470 MUST be working for same reasons above;

Have done all the obvious like checking all solder joints under a microscope and resoldering anything that looked suspect but as per previous paragraph, all MUST be working on the 470.

The only thing I can't do is check operation of the SPI 2 functionality as I do not have any other SPI devices to test against.

Any thoughts/comments or a good source of replacement hair greatly appreciated.
Doug.

... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it!

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2932

Posted: 08:09pm 23 Nov 2016

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Doug, I will be building one very soon and will report back . . . .

panky

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Joined: 02/10/2012
Location: Australia
Posts: 1114

Posted: 11:11pm 23 Nov 2016

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I am ashamed to admit that I screwed up! The TFT mounts on the TOP of the board, over the 470 and other components. I had it on the bottom. In my defence, the picture of the board on page 70 is misleading as the ICSP conector is shown on the top or component side and the SD card as being on the bottom even the the TFT connector is shown on the top.

My error but bad design in my humble opinion as all component markings are on the top and subsequently under the TFT which is dumb.

Sorry to waste anyones time so BEWARE, make sure you put the TFT connectors CON3 and CON7 on the FRONT of the board and the I/O and additional I/O (CON2 and CON 6) together with the ICSP (CON 4) and any other connectors on the back of the board where there are only connector and pin numbering!!!

Doug.

... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it!

WhiteWizzard
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Posts: 2932

Posted: 11:16pm 23 Nov 2016

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Thanks for pointing out that 'gotcha' - no doubt there will be others that make this mistake too; as no doubt I would have done if it wasn't for this post.

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3282

Posted: 11:53pm 23 Nov 2016

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These sorts of things happen - but in their defence the photos on pages 64 and 72 leave no doubt as to how the board should be assembled and the photo on page 70 shows everything correctly mounted (ie, everything goes on the component side except CON 1, 2 and 6).

I hope that you managed to desolder the connector without damaging the board, it is very hard to remove components from plated thru holes.

Geoff

Geoff Graham - http://geoffg.net

panky

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Joined: 02/10/2012
Location: Australia
Posts: 1114

Posted: 12:18am 24 Nov 2016

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Thanks Geoff,

Yes, entirely my fault

However, all's well that ends well! Got the connecters out (destroyed) but saved the holes OK and replaced said connectors, THE RIGHT WAY ROUND

and all is working as it should.

That said, I still feel that the TFT on the top is the wrong way to go, particularly if you need to do any fault finding, probing with a CRO or eyeballing joints etc. Just my two penneth worth

Doug.

... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it!

Geoffg

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Location: Australia
Posts: 3282

Posted: 02:20am 24 Nov 2016

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Yes, good point. The Micromite LCD Backpack is the same.

Geoff Graham - http://geoffg.net

WhiteWizzard
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Posted: 02:23am 24 Nov 2016

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Just assembled one here, and thanks to Doug's post/warning, it worked first time

Loaded with v5.3B3 and woking fine so far

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