Re: TDA2822 Audio problem #ubitx #tda2822

Jerry Gaffke
 

The USB-to-UART cables sold for use by Arduino hobbyists generally have 0-5v logic levels,
not RS232.   That thing on Oddwires I suggested in a previous post:
    http://www.oddwires.com/cp2102-serial-adapter-module-usb-to-rs232-with-jumper-wires/
claims to be "USB to RS232", but I seriously doubt it.  All I see is the SiLabs chip on it,
no level translators.  Could be 5v logic levels, could be 3.3v, or could be configurable.
Claims to be suitable for use with both the Rasberry Pi (3.3v) or Arduino (5v).
These are nasty hardware details that everyone in the Arduino universe is oblivious to.

I have an old TTL-232R-3V3 FTDI cable I use,
    http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf
since 3.3v and less is what most of electronics have gone for the last couple decades.
For use with the Nano, we should have the 5v logic level version, the TTL-232R-5v
FTDI is kind of the industry standard, note that the true Arduinos have the same FTDI chips.

Better yet, here's a newer FTDI cable that can be configured for either 5v or 3.3v:
    http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232RG_CABLES.pdf

Those FTDI cables are around $20.
FTDI clones and alternatives are now out there for $2 or $3.
If that's a real SiLabs chip on the Oddwires device it probably works fine,
though Oddwires hasn't bothered to fully describe what the logic levels are.    

Jerry, KE7ER


On Tue, Apr 10, 2018 at 09:18 am, Arv Evans wrote:
Beauty of using the built-in UART and built-in USB interface on an Arduino NANO is
that you don't have to mess with voltage level conversion between RS-232 and TTL.
This is also convenient because many modern PC do not have built-in RS-232 ports.

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