[avrdude-dev] [patch #7559] 'arduino' programmer type DTR transition fix

[Robert Spitzenpfeil]

Follow-up Comment #17, patch #7559 (project avrdude):

I have abandoned windows almost completely.

The only way I can run it is inside VirtualBox, and I don't think it is wise
to use that as reference.

Identical behaviour across platforms is a very good thing!

According to wikipedia, the RS-232 _control signals_ are not inverted.

[...]

When one of these signals is active [DTR...], the voltage on the line will be
between +3 to +15 volts. The inactive state for these signals is the opposite
voltage condition, between −3 and −15 volts. Examples of control lines
include request to send (RTS), clear to send (CTS), data terminal ready (DTR),
and data set ready (DSR).

[...]

So I would think that translating that to 0...5V would be just scaling and
shifting the voltage interval without inversion.

I would assume that ser_set_dtr_rts(1) would therefore set the line HIGH
(active), and ser_set_dtr_rts(0) to LOW.

Why the low-level register writes are inverted on linux I don't know. I'm
trying to find out why that is the case. Finding the right kernel mailing list
is a tedium.

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