Can't Read Device Signature on Custom Board

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Hi, I'm a newbie making a custom board for the first time and I realize I've made several somewhat serious mistakes, but I'm hoping to learn from them.

 

I'm trying to program the ATSAMD21E17A using Microchip Studio with JTAG. My (known) crimes are that I didn't use any bypass capacitors on the microcontroller and I didn't add a pull up to the SWD clock (the datasheet says to for reliability) or the reset pin. I checked that the microcontroller was adequately powered with a 3.3 V supply on board and I was able to read it with Microchip Studio using the JLink EDU. I've attached a schematic for reference.

 

Does anyone know if I can still program this somehow? If not, what is really causing the problem- the caps, the reset, or something I missed?

 

Any help is greatly appreciated and critiques so I can improve as an engineer are welcome.

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Last Edited: Sat. Apr 3, 2021 - 07:52 PM
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hardE wrote:
Hi, I'm a newbie making a custom board for the first time

Welcome to AVRFreaks!

 

I'm not sure when the practice of putting individual parts on a drawing and linking with net names began, but a real schematic tells a story, a complete story!

It's no surprise to see/hear you have left critical parts off your schematic drawing, had it been a schematic it would have been obvious to anyone there is something missing from the story.

My suggestion would be, go back, start over and DRAW a schematic with all the lines needed to connect ALL of the parts that make up the project.  This will be the best way to fix the problem, and in the end you will have a working board.

At least you now know the process of getting a drawing to a layout, to a physical board, so that is a start and further then many other beginners that have not done that. 

Making PCB, is a lot like making pancakes, you throw the first one away!

Good luck.

Jim

 

 

 

FF = PI > S.E.T

 

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Thanks for the feedback, Jim, I'll certainly do that in my next iteration to make it professional.

 

Do you know if this one is still programmable though or what is really preventing Microchip Studio from reading the device signature?

 

Best,

Neil

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Update: I've soldered a pull-up resistor on the board and got a new error. I still can't get the device signature, but now I get the following message:

 

Timestamp:    2021-04-02 15:00:24.316
Severity:        ERROR
ComponentId:    20100
StatusCode:    3
ModuleName:    TCF (TCF command: Device:startSession failed.)

'ArmDev_4' is not a device context.

 

The StatusCode changed from 1 to 3 and, interestingly, the number following "ArmDev_" (I'm on 4 now) increments every time I try to read the device signature. It's safe to say I'm very confused and would appreciate any insight into what is going on here.

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Nevermind, I drove the reset low and I'm back to the same error

 

Timestamp:    2021-04-02 15:31:09.212
Severity:        ERROR
ComponentId:    20100
StatusCode:    1
ModuleName:    TCF (TCF command: Device:startSession failed.)

Error connecting to device over SWD

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SWCLK is on PA30, SWDIO on PA31, you have this swapped.

/Lars

 

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Wow I can't believe I did that. Thank you Lars!