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Forum Index : Microcontroller and PC projects : PicoMite VGA Edition PCB - release version

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palcal

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Joined: 12/10/2011
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Posts: 1965
Posted: 02:43am 20 Apr 2022
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From the BOM
  Quote  Q1, Q2 n-channel enhancement mosfet, max GS threshold 2V
Tested with BST72A and silkscreen matches this part. Suggest TN0702N3-G Farnell 2920846 £1.25 = £2.5 (check pinout against silkscreen)


Farnell/Element14 dont seem to stock either of these parts anyone found a suitable replacement.
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
al18
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Joined: 06/07/2019
Location: United States
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Posted: 02:52am 20 Apr 2022
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Mouser has over 3000 in stock in the US
 
palcal

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Posted: 03:21am 20 Apr 2022
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The freight from USA to Australia is too much. $20 or more.

I can probably source a SMD device that I could solder in, I haven't checked yet
just thought someone may have a through hole replacement.
Edited 2022-04-20 13:24 by palcal
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
Turbo46

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Posted: 03:29am 20 Apr 2022
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2n7000 can be used. Altronics and Jaycar both have them but note the orientation is different.

Bill
Keep safe. Live long and prosper.
 
palcal

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Posted: 03:34am 20 Apr 2022
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Thanks, Bill.
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
palcal

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Posted: 04:43am 28 Apr 2022
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I ordered the SD card breakout board from Element14/Farnell part no. 279-9953
It is different to the one shown in the photos. I can't read the silk screen on matherp's photo and the scematic in the ZIP file is .sch format that I can't open.
Here is a picture of what I have. I think I will have to offset it but do the pins match up. There was no photo on the Element14 site so I was flying blind.



Edited 2022-04-28 14:48 by palcal
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
Volhout
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Posted: 05:53am 28 Apr 2022
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Hi Pascal,

Your sd card board is capabele of 5v. The board that Peter designed is 3.3v
So you have the wrong board.
But you may be able to get it to workshop by tying 5v and 3.3v pins together to 3.3v.
And you may have to swap pins in the Option sd card definition.

Volhout
PicomiteVGA PETSCII ROBOTS
 
Turbo46

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Posted: 05:54am 28 Apr 2022
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I got the one specified from Core Electronics.

The pin layout is different and yours has a voltage regulator and level shifting which are not needed for Peter's board. There is a datasheet on the Element14 site for info on the one you have.

Bill
Keep safe. Live long and prosper.
 
palcal

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Posted: 07:55am 28 Apr 2022
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I have an account at Core Electronics will order from them.
Thanks
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
Chopperp

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Joined: 03/01/2018
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Posted: 08:25am 28 Apr 2022
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Out of stock at CORE ATM

Did you get the last one?
.
Edited 2022-04-28 18:27 by Chopperp
ChopperP
 
Amnesie
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Posted: 08:35am 28 Apr 2022
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  Volhout said  Hi Pascal,

Your sd card board is capabele of 5v. The board that Peter designed is 3.3v
So you have the wrong board.
But you may be able to get it to workshop by tying 5v and 3.3v pins together to 3.3v.
And you may have to swap pins in the Option sd card definition.

Volhout


I am using this Adafruit Sd Breakout on ALL my picoMite builts. It works perfectly with 5V directly, since it has own level shift but it also works via 3V3 on the corresponding pin. In my opinion this is the ultimate breakout because it is ready for every voltage. Of course it is a slightly different pinout than the black (3v3 only) version for which the original picoMite VGA PCB was desigend for.

So in short: the Adafruit blue version does work, but it won't fit the pinout on the board.

Greetings
Daniel
 
palcal

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Posted: 07:03pm 28 Apr 2022
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Yes must have got the last one.
@ Amnesie, thanks for that at least it is not a loss.
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
Volhout
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Posted: 08:35pm 28 Apr 2022
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Pascal, I was impatient....


PicomiteVGA PETSCII ROBOTS
 
palcal

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Joined: 12/10/2011
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Posted: 08:43pm 28 Apr 2022
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I think we have all done wiring like that at some time.
Edited 2022-04-29 06:45 by palcal
"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"
 
Turbo46

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Joined: 24/12/2017
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Posted: 11:27pm 28 Apr 2022
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One way to use a different breakout would be to make a carrier board out of strip board which will fit the mounting for the specified board and fit the alternative board on top of that with the cross patching done on the strip board. That will allow you to fit the correct one later if you want.

Bill
Keep safe. Live long and prosper.
 
Volhout
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Posted: 07:41pm 03 Jun 2022
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  robert.rozee said  so the layout (looking into the connector from the front) is something like the below?

   (1)          (2)  
   GP0   x  x   GP1
   GND   x  x   GP2
   GP3   x  x   GP4
   GP5   x  x   GND
   GP6   x  x   GP7
   GP8   x  x   GP9
   GND   x  x   GP10
  GP11   x  x   GP12
  GP13   x  x   GND
  GP14   x  x   GP15
  GP16   x  x   GP17
   GND   x  x   GP18
  GP19   x  x   GP20
  GP21   x  x   GND
  GP22   x  x   nRST
  GP26   x  x   GP27
   GND   x  x   GP28
ADCREF   x  x   3v3
 3v3EN   x  x   GND
  VSYS   x  x   VUSB
  (39)          (40)


cheers,
rob   :-)



I think I am confused. When I look at the board layout in the first post of this thread, I can clearly see that 3.3V is routed to pin 25 (or 26 when the pin numbers are mirrored). In this drawing it is on pin 36. Is the board layout in the first post not the last layout ?
PicomiteVGA PETSCII ROBOTS
 
matherp
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Joined: 11/12/2012
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Posted: 09:34pm 03 Jun 2022
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  Quote  I think I am confused.


No, you have spotted a complete f-up that for reasons unknown nobody else has seen before. Pins 21-40 are all completely wrong on the edge connector. I'll post a revised version once I fix it
 
Volhout
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Posted: 07:37am 04 Jun 2022
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Peter,

Not sure if it pays off to change the board layout in this phase, unless you have other reasons to do so. Maybe we should just document what it is, and leave it at that. The early adopters all have this version. And it is unsure how many will build the new version and throw away the old. So you end up with a mix best case. Or you spend a lot of time and no-one uses it.
It feels a bit like the CMM2 revision 1 and revision 2 incompatibility.
PicomiteVGA PETSCII ROBOTS
 
robert.rozee
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Joined: 31/12/2012
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Posts: 2398
Posted: 08:29am 04 Jun 2022
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i believe there are already multiple 40-pin connector pin layouts for the various pico carrier boards.


cheers,
rob   :-)
 
JohnS
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Joined: 18/11/2011
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Posts: 3994
Posted: 10:27am 04 Jun 2022
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I'm confused too - what is the layout for the current connector?
(on Peter's board)

John
 
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