Hi Peter,
On 2020-03-15 20:19, Peter C. Wallace wrote:
On Sun, 15 Mar 2020, Rafael Skodlar wrote:
"... The outputs are push pull CMOS that will drive to the output
supply rail of 3.3V. This is sufficient for TTL compatibility but may
cause problems with some types of loads. For example when driving
an LED that has its anode connected to 5V, in such devices as
OPTO isolators and I/O module rack SSRs, the 3.3V high
level may not completely turn the LED off"
You left off a bit of the manual text:
"To avoid this problem, either drive loads that are ground
referred, Use 3.3V as the VCC for VCC referred loads, or use open
drain mode."
Peter Wallace
Mesa Electronics
I did see that but did not want to repeat too much here. It would be
nice to have a block diagram though. I prefer diagrams over long
descriptions. If nothing else, it's easier for international users to
see how to connect that board to PC, SBCs, or RPi, etc. than reading a
description in another language.
What I'm concerned about is that noise on power and some other lines can
be bigger than 3.3V which can result in totally unexpected side effects.
Scratch your head on a dry hot day and you can generate more than 3V of
static electricity that can kill LVD chip if you touch it.
I would rather see a board that's designed for 5V and above. 6, 9, 12V
IO for driving relays, motor drivers, or other things. That would be
more robust than adding yet another board just to convert voltages
especially if IO pinouts are not standard.
Thanks for responding,
--
Rafael Skodlar
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