ESP Efuse : Get selected efuse value as JSON object

[sbertrand-witekio]

Description of change

Addition to get efuse value as JSON object for further processing

I have tested this change with the following hardware & software combinations:

Linux, ESP32, WROOM, WROVER

Comment

This allow to get efuse value so script can flash devices appropriately depending on secure boot or flash encryption state of the device.

[mahavirj]

CC @ghemal

[projectgus]

@sbertrand-witekio Thanks for sending this PR. We've been discussing the need for something similar internally, specifically a machine-parseable output for the efuse values.

Rather than having a command that reads a single efuse as JSON, what about adding an option to the existing summary command like --format=json that dumps the summary of all efuses as a JSON dictionary rather than the current human-readable table?

The main advantage would be that a single JSON file can contain machine-parseable data about all efuses. This will be much more convenient for any use case that involves reading more than one efuse at a time, because espefuse.py doesn't have to re-connect to the bootloader on each invocation.

I look forward to hearing what you think about this idea.

[sbertrand-witekio]

That would be fine. I was just concerned about processing time, efuses are read from the device one at a time or in blocks then parsed by Python ?
Can there be an option to export to a file as well ?

I have added other processing for the MAC address, to get the raw data was hex, as to avoid further processing.

[projectgus]

@sbertrand-witekio

In terms of runtime, nearly all of the time is spent connecting to the ESP32. Fetching the efuse information from the chip is quite fast.

Are you interested in updating this PR along the lines of what was discussed?

Angus

[sbertrand-witekio]

Hi,
I can update the PR with those changes
efuse summary :

• [--format=json] to get a json output
• [--file=filename] to get export in a file

I'll work on this this week.

[sbertrand-witekio]

I have updated the PR.

[projectgus]

Thanks for that! Left a few minor comments but it looks pretty good.

Please also check the Travis CI output for flake8 warnings, etc.

[sbertrand-witekio]

I have fix the coding style based on the feedback.

[sbertrand-witekio]

I have made changes based on the feedback.

[projectgus]

Thanks @sbertrand-witekio !