BOOT SIGNAL OPERATION AND ARTEMIS REDBOARD SCHEMATIC INCONSISTENCIES?

Development Boards Artemis
1

I am looking at the Artemis schematics and comparing them to the board on my desk. They don’t match up when it comes to the generating the BOOT signal. The eagle schematics for the Artemis Redboard, Nano, and ATP show that one of the resistors is “DNP”, which I assume means “Do Not Populate”, while the other is listed as being 220K. The cap is shown as a 0.1 uF.

In contrast, measuring the components on my Artemis blackboard shows a 100K resistor in the DNP position, a 10K resistor in the 220K position, and a 2.2 uF cap instead of a 0.1 uF cap.

To add to the mystery, I found a PDF schematic of the Artemis Nano on the Sparkfun website that shows the circuit with a 100K R, a 10K R and a 2.2uF cap. That is not what the Eagle schematic shows for that exact same board, but it does match the components I found on my blackboard.

Which version is correct? Is there documentation on how the BOOT circuit is supposed to work? I could not find any, but when BOOT is one of the search terms it gets a lot of hits…

I have attached a PDF of what I am talking about with snippets from both versions of schematics.

2

The design of the auto-bootload circuit has varied slightly over time. The purpose, however, remains the same: to allow the Artemis bootloader to be actuated by a signal on just one pin (for USB->Serial chips such as the CH340E which only have one available control pin).

This means that doing something on one line should both reset the Artemis and make sure the boot pin is in the correct state to enter the bootloader. The RC circuit on the boards achieves this and changes in values just affect the exact timing. The latest design is the one you will find on the Red products (rather than the experimental SparkX products in black).

Some bootloader settings can be modified in the Apollo3 using a debug probe. These include the baud rate and polarity of the BOOT pin for example.

As for exact values I would trust the Eagle files from the design repos the most. The schematics could potentially just be out of date

Here’s a little more relevant info:

https://github.com/sparkfun/SparkFun_Ap … #L411-L442