PIC-P28-USB device support?

Started by SM6NNC, May 07, 2020, 10:48:56 am

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SM6NNC

A humble question upon which devices that can be used on the PIC-P28-USB - board (and, I guess, right the same on the PIC-P28 - board?)

The spec under "Features" says:
Supports all 28-pin PIC microcontrollers in PDIP package (but NOT SPDIP package!)

But what do You read into PDIP vs SPDIP?

I'm considering some experiments using a PIC 18F27K42-I/SP. The data of this circuit says it is in a SPDIP socket, and reading specifications, this is a 28 pin DIL-circuit with row-spacing 0.3" and pin-spacing 0.1"

As far as I can judge, the pin-out on the P-28 board seems to be just the same, or am I mistaken? Is there any other snag besides pin-spacing?

LubOlimex

May 08, 2020, 08:52:50 am #1 Last Edit: May 11, 2020, 02:17:01 pm by LubOlimex
28-pin SPDIP would not fit out-of-the-box. The chip is too narrow at 0.3". The PDIP version of the 28-pin chips is double the size at 0.6". The socket on PIC-P28-USB is at 0.6".

Edit: 28-pin SPDIP (0.3") would fit out-of-the-box but you would have problems with PDIP (0.6").

Compare the size of 28-pin chips in each package here:

https://www.microchip.com/quality/packaging-specifications?packageFamily=PDIP

https://www.microchip.com/quality/packaging-specifications?packageFamily=SPDIP

Now you can try to bend the pins a bit, but the last time I did that I broke the chip. Maybe using a socket adapter is also possible but I haven't seen one to recommend, you might have better luck in finding such 28-pin adapter at 0.1" step from 0.6" to 0.3" width.
Technical support and documentation manager at Olimex

SM6NNC

But, but...

The picture I can see of a PIC-P28 shows a socket 2 rows x 14 pins = 28 pins.

Spacing pin - pin is 0,1", (2,54 mm), just as the holes in the grid around.

Spacing row - row equals 3 pins in pin - pin, ie 0,3" (7,62 mm).
This is extremely clear in looking at the rear side of the PCB. 3 Rows of pads...

This is in contrast to the PIC-P40, which really has 0,6" spacing with its 2 x 20 connections.

So, to my opinion, the 18F27K42-I/SP (28 pin, 0,3" spacing) should fit the socket on a PIC-P28 board. Am I totally mistaken, or could the description of this board be improved?

The only "problem" I see is that the X-tal will have to be changed from 20 MHz to 16 MHz in order to operate this circuit with external X-tal at full speed ( 4 x X-tal = 64 MHz ), where the 4 x PLL in the PIC requires Fmax = 16 MHz. With 20 MHz X-tal, max possible external CPU-clocking will be 20 MHz.

Bending circuit legs from 0,3" to 0,6" must be impossible - the legs are just to short to do that. But trying to bend from 0,3" to 0,4" might be tempting.

LubOlimex

Technical support and documentation manager at Olimex

SM6NNC

Please have a look at the data for this CPU:
http://ww1.microchip.com/downloads/en/DeviceDoc/PIC18LF26-27-45-46-47-55-56-57K42-Data-Sheet-40001919C.pdf

Page 776 (chapter 46.1) gives "Package Details". The label is:
28-Lead Skinny Plastic Dual Inline (SP) - 300 mil Body [SPDIP]
pitch is given letter "e" in the figure.

LubOlimex

Ok but the problem is not the pitch. The pitch in both packages is 0.1".

The problem is the "Overall row spacing" (eB) which in PDIP is max 700 mils and in SPDIP max 430 mils.
Technical support and documentation manager at Olimex

SM6NNC

Agree;
PDIP means 600 mill, E (shoulder to shoulder distance) = 0.610" nominal
SPDIP means 300 mill, E (shoulder to shoulder distance) = 0.310" nominal

The text describing the Olimex PIC-P28 board says:
With this board you can develop and prototype with all Microchip's PDIP28 PIC microcontrollers (note that the board is not suitable for SPDIP28 microcontrollers!).

"Not suitable for SPDIP28"? In my looking on the picture, it is right the opposite: The picture shows 300 mil distance, so the board should  be "not suitable for PDIP28"

For the Olimex PIC-P28-USB board, the first point under "Features" says:
Supports all 28-pin PIC microcontrollers in PDIP package (but NOT SPDIP package!)

The processor socket on this card is just as wide as the DIL-8 socket for a SPI memory. I would say that a 600 mil (PDIP) fits less well here also, only a SPDIP (300 mill) would fit, but your text says the opposite.

LubOlimex

Oh yes, my bad. You are correct. It should be SPDIP only, no PDIP. Fixed now. My apologies.
Technical support and documentation manager at Olimex

SM6NNC

Such things can easily happen. As long at they get corrected, life continues well.

I've seen that you have corrected the presentation of the PIC-P28-USB, but just the same goes for the older PIC-P28-20MHz, whose text also needs some touch-up.

Best wishes, and thanks for excellent support

/Göran

LubOlimex

Added a note there too. Thank you for the contribution. Let me know if you find other discrepancies.
Technical support and documentation manager at Olimex

SM6NNC

Hi,
Yes, the PIC-P28-20MHz now has a "Feature" that is just right.

But, the description (to the right on Web-page, below prices) starts with:

With this board you can develop and prototype with all Microchip's PDIP28 PIC microcontrollers (note that the board is not suitable for SPDIP28 microcontrollers!).
(My bold-facing).
This would need some adjusting!
Some resellers seems to "Cut and paste" this text right off, so getting it right would also be an advantage.

All my best,
Göran