Re: Looking for recommendations: schematic reading turotial

Paul Keinanen wrote:
"Adrian" <adrianbica@xxxxxxxxx> wrote:
"Ignacio G.T." <igtorque.rem...@xxxxxxxxxxxxxxx> wrote:

By concentrating his/her efforts in the application part and
leaving the "low level details" to real men/women of the same
team?

Then he/she is not "experienced"!

Embedded systems are quite often tested using a row of switches
to simulate binary inputs, potentiometers to simulate analog
transducer signals and LEDs for monitoring digital outputs. In
order to test an embedded software using these tools, very little
knowledge of electronics is needed, but still you may have to
write device drivers etc.

The software designer in a team does not usually have to worry
about galvanic isolation, input protection and EMC filtering,
which are done specialised HW people.

Still it helps if the software designer is able to look at the
circuit diagram, e.g. to determine if the buffer stage between
the processor pin and the external (say 20 mA) circuit is
inverting or not, in order to write the correct polarity into
the output register.

To illustrate the importance of knowing something, some years ago I
arrived on a job to create PIC software. Most things had already
been laid out, and prototype boards made. I found a circuit
inputting push buttons from a panel where there was a pull-up
resistor and a capacitor to ground on the input pin.

I made some fuss about this, and got a series resistor added from
the actual switch. The problem would not have shown up until some
time in the field, when the inrush current from the capacitor
discharge would have welded the switch contacts, leading to a poor
quality reputation.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net>



--
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