[time-nuts] Thunderbolt/Arduino RS232 Interface Issue

Tom Harris celephicus at gmail.com
Wed Jun 3 02:21:04 EDT 2015

You have TX connected to TX? Swap your TX/RX connections and see if the
levels improve.

Tom Harris <celephicus at gmail.com>

On 3 June 2015 at 14:38, Dan Quigley <danq at quigleys.us> wrote:

> Hello,
> I'm integrating an Arduino (Due/Mega have tried both) with a surplus
> Thunderbolt and need some advice.
> The Thunderbolt is a known working unit (supplies 10Mhz to my HPSDR rig)
> and the serial interface works fine between it and a PC.  I've read the
> coverage about this kind of integration (and some of the archived
> discussions on this board) and am employing a commercially available
> MAX232-based "shield" (RS232 V2) to handle the level translations.  Just
> three lines (RX/TX/GND) are  used.  The MAX232 circuit is working, reliably
> passing data between the Arduino and a PC.
> With the Thunderbolt is connected to the MAX232 no data passes.  Activity
> LEDs on the non-RS232 of the MAX232 circuit show no activity when the
> Thunderbolt is providing data, indicating the MAX232 is not performing the
> intended level translation.  I've scoped the RX/TX lines coming from the
> Thunderbolt both when connected to the Arduino and not.  There is a
> distinct difference. When disconnected, the pulses are about 10.3v and
> nice, crisp and square.  Connected, the pulses are ~50% lower in voltage
> (4.1v) showing an exponential rise in voltage and trace noise.
> I'm pretty much stumped at the moment and wonder if anyone can offer a
> suggestion or thoughts on a direction to take.
> Thanks in advance,
> Dan Quigley (N7HQ)
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