Feather M4 express bootloader

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akki0075
 
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Feather M4 express bootloader

Post by akki0075 »

Hi,

Earlier i was using feather atmega32u4 with lora based module. I guess that MCU doesn't have bootloader pre-installed right?

Now I am using Feather M4 express and in the documentation, it is mentioned that bootloader has to be installed first. My question is doesn't this MCU come with pre-built bootloader from the manufacturer?

Also, I checked this MCU at Microchip tech's website and it doesn't have JTAG capability, which verifies the designs and testing of PCB after manufacture. So do you some sort of customized JTAG here in the feather which carries out installing bootloader and testing the code?

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adafruit_support_mike
 
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Re: Feather M4 express bootloader

Post by adafruit_support_mike »

The Feather M4 comes with a pre-installed bootloader. There are instructions for updating the bootloader or installing the latest version of CircuitPython, but those use the existing bootloader.

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akki0075
 
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Re: Feather M4 express bootloader

Post by akki0075 »

Hi,

I am making my PCB design with ATSAMD51 micro controller and I believe digikey.com sells the same MCU without bootloader. So when PCB comes to my hand after manufacturing, it might be w/o bootloader. So is there any way I can install the same UF2 bootloader using instructions given in your website?

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adafruit_support_mike
 
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Re: Feather M4 express bootloader

Post by adafruit_support_mike »

You’ll need to use a JTAG pod:

https://www.adafruit.com/?q=jtag

Our bootloader is free to use, and you can find it here:

https://github.com/adafruit/uf2-samdx1

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akki0075
 
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Re: Feather M4 express bootloader

Post by akki0075 »

Great Thanks!

One quick question though!

I saw the microUSB circuit on the schematic. As per my understanding, firstly, D+ and D- are going to the micro-controller and I believe those connections are for flashing the code into the chip right? Secondly, what is the purpose of those differential pair test pads connected to the microUSB?

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danhalbert
 
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Re: Feather M4 express bootloader

Post by danhalbert »

D+ and D- are the ordinary data lines for USB data.

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akki0075
 
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Re: Feather M4 express bootloader

Post by akki0075 »

So you mean when this MCU is connected to the computer through USB port and I am flashing the code through Adruino IDE. The code is basically being flashed to the M4 through these D+ and D- pins connected to M4 right?

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danhalbert
 
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Re: Feather M4 express bootloader

Post by danhalbert »

Right, but those pins are used for -all- USB data, whether it's flashing, serial, USB drive, HID, etc.

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akki0075
 
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Re: Feather M4 express bootloader

Post by akki0075 »

Perfect, but why you have provided the test pads for those pins. Whats the benefit of it?

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danhalbert
 
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Re: Feather M4 express bootloader

Post by danhalbert »

akki0075 wrote:Perfect, but why you have provided the test pads for those pins. Whats the benefit of it?
You might, for instance, be mounting the board inside a box, and want to route the signals from the board to a panel-mounted USB jacks. They are not test pads so much as convenient access points

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westfw
 
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Re: Feather M4 express bootloader

Post by westfw »

why you have provided the test pads for those pins. Whats the benefit of it?
Also, presumably: testing? I don't know what Adafruit does for testing of a Feather M4 after they're made, but dropping it into a test fixture, burning the bootloader, and checking whether USB works seems like a good start!

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akki0075
 
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Re: Feather M4 express bootloader

Post by akki0075 »

Got it!.

Also, I was looking at the p-type MOSFET you are using in Power and filtering, can you somehow give an info. like which exactly you are using and its manufacturer?

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danhalbert
 
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Re: Feather M4 express bootloader

Post by danhalbert »

Schematic (https://learn.adafruit.com/adafruit-fea ... /downloads) says the MOSFET is DMG341 (which is an imprecise part number), but I think after looking it up we might be using a DMG2305UX now (from Diodes Incorporated). But I am not completely sure.

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akki0075
 
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Re: Feather M4 express bootloader

Post by akki0075 »

So after looking at this mosfet, drain to source voltage is 20V? This means we can even use the battery which gives more than 3.3V to the mosfet right?

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danhalbert
 
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Re: Feather M4 express bootloader

Post by danhalbert »

The board is meant for use with a 4.2V LiPo battery, and has a charger for that kind of battery.

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