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From prototype feather boards to one PCB board
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Please be positive and constructive with your questions and comments.

From prototype feather boards to one PCB board

by IoTAll on Thu Jul 23, 2020 1:13 pm

Hi!

I have been having a lot of fun using Adafruit feather boards and other breakout boards and I am now done with one project with everything working good. (after many trials and errors).

I would like to discover now how to convert from the prototype boards that I am stacking or connecting to a one single PCB board with all components on it, based on Adafruit prototype designs. I see there are the Eagle files that I can download.

I am not very sure where to start and I feel like this is going to be a big and very interesting step forward :)
I would like to precise that I want to keep this as a hobby.

Any guidance to give me the first directions would be great!!

Thanks!!

IoTAll
 
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Re: From prototype feather boards to one PCB board

by friesenelectric on Fri Jul 24, 2020 11:07 am

I am looking for the same answers as you. I am using a Feather M0 with LORA as a development board, but where do I go from here? I need about 200 devices. Right now I have programmed in circuitpython and everything is working great, but how do I do the same thing with PCB?

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Re: From prototype feather boards to one PCB board

by westfw on Sat Jul 25, 2020 12:23 am

I would:

Download the board that you are interested in using as the base for your design.
If you want to keep "layout hints", edit the .brd file to remove things like the Adafruit logos, mounting holes, prototype areas, extra silkscreen layers, etc. Save this as "feather-bare" or whatever, in case you want to do something else.
"Save as" the new board name that you want as well. (and then "save all" so you have both .sch and .brd.)

If you're going to lay things out completely from scratch, you can just copy the .sch file to your new schematic without the .brd file, and then use "switch to board" are "create board from schematic" to put the components on a unrouted and unpositioned board.

Now start deleting the components that you don't need from the schematic. (and the boilerplate. Adafruit schematics usually have nice letter-sized frames, and if you don't have a better-than-free version of Eagle that lets you make other schematic pages, that may be an unacceptable space-stealer.)
Add your own components (copy/paste from some other schematic, perhaps?), and eventually go to the board and move everything around, routes, add your own special silkscreen layers, etc...

Done!

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Re: From prototype feather boards to one PCB board

by IoTAll on Sat Jul 25, 2020 1:30 pm

Hi!
Thanks for the help!!

My goal is to have the PCB card completely made with the components welded on it when I receive it.

I was looking for instance into the M0 feather board and downloaded the Eagle files.
Then searching on the web, I understood that the list of the components used can be found in the schematic view, then clicking on "DESIGN LINK/Schematic".

But I cannot find the main components listed, like the ATSAMD chip for instance. I might not be looking at the right place.
It is not the goal at all as I will buy Adafruit parts as long as I can as I love their products but to understand: using the files of those boards provided, it is possible to manufacture those by sending it to manufacturers? Or is it needed to add more information.

More to dig in :)

Any tips again, more than welcome and thanks for sharing!!

IoTAll
 
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Re: From prototype feather boards to one PCB board

by westfw on Sat Jul 25, 2020 6:14 pm

Ah. I was assuming more familiarity with EAGLE. CAD packages have a pretty steep learning curve, and you're trying to do a lot at once.

I have never had a board fully manufactured by anyone; the closest I've come is getting the bare boards made for me, and soldering the components on, myself.

And the version of EAGLE I'm using is an older, "non-profit" version, which doesn't have the "DESIGN LINK" feature you mention...

My GUESS is that the newer EAGLE supports some features for automating some of the manufacturing process, BUT it's dependent on using annotated part libraries with a lot of extra data added ("Manufacturer part number", etc.) AND Adafruit doesn't use such libraries. I know that EAGLE has added features (like "attribute") aimed at storing additional information about parts.

I see this frequently in comments by professional designers when they talk about things like the Arduino "reference designs." "There's no BOM (Bill Of Materials)! How do I know which resistor to use if there is no BOM?? Freaking Amateurs!!!" And we Amateurs are pretty much "stop panicking! It's a generic 0805 10kohm resistor. What more do you need?"
The detailed BOM seems to be more important when you're having some other company manufacture the "thing" for you. You might want to specifically specify that some parts are generic, while others are "do not substitute!" And professional manufacturers will have ways that they want that all to be laid out (not necessarily the same as other professional manufacturers, alas. "To be negotiated.")
I don't know what the "new" "we'll assemble your board for you" services do. Hopefully they document it. In English.

Since Adafruit does their own manufacturing, they can bypass some of the formalities. (assuming that the published schematics match their internal schematics, WRT BOM information. Given their politics, I'd assume that they do match. Arduino's don't, though.)

I think you can get some of the information you're looking for using the "RUN BOM" command in the EAGLE Schematic, assuming that's still present:
Screen Shot 2020-07-25 at 3.04.58 PM.png
Screen Shot 2020-07-25 at 3.04.58 PM.png (404.5 KiB) Viewed 24 times

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Re: From prototype feather boards to one PCB board

by adafruit_support_mike on Sun Jul 26, 2020 4:53 am

westfw wrote:I see this frequently in comments by professional designers when they talk about things like the Arduino "reference designs." "There's no BOM (Bill Of Materials)! How do I know which resistor to use if there is no BOM?? Freaking Amateurs!!!"

Professionals who say that have probably never had a board fabricated by an assembly house.

One *very* standard part of working with an assembly house is adapting your BOM to use as many house brand parts as possible. There's no way they'll keep an inventory of Bourns/KOA/Panasonic/Rohm/Vishay/Xicon/Yageo thick/thin film resistors so you can call out a specific kind. They will have an inventory of a specific brand whose behavior they already know though, and which are already in feeders for the pick and place machines. Using house-brand jellybeans costs less because you only have to pay for the actual number of parts you use, not full reels, and you won't have to pay setup costs for loading the reels into and out of the feeders.

We don't publish a BOM because ours are written in terms of our own inventory, and we often get parts from companies who only deal in Minimum Order Quantities of 10k to 15k, and quote lead times of six weeks or more. We also change sources occasionally, so the exact part number and manufacturer for a 10k 0805 today might be different from the one we'll use a year from now.

If anything about a part isn't generic, we call it out with a note in the schematics. I don't know any design that needs more information than '10k, 1%, 0805' to work though. Callouts are more common for things like the low-voltage Schottky diodes between a Feather's VBAT and VBUS signals (the MBR120).

Broadly speaking, asking for a BOM is like going to McDonalds and asking for a supplier list so you can buy the same things. Even if they gave it to you, knowing the factory that makes chicken nuggets buys MSG from DuPont in 5-ton lots of 55-gallon drums wouldn't be particularly useful for stocking the average home kitchen_.

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Please be positive and constructive with your questions and comments.