[Noisebridge-discuss] cheap USB Analyzer, or signal integrity tools?

[Dr. Jesus]

On Mon, Nov 8, 2010 at 1:22 PM, Andy Isaacson <adi at hexapodia.org> wrote:
> On Mon, Nov 08, 2010 at 01:17:03PM -0800, John E wrote:
>> Are you talking about during assembly or during use?
>> A couple of diodes in the input stage to protect against being blown up by
>> static or wrong voltages,
>
> I'm not an EE, but it's my impression that building a decent input stage
> for a 0.5 - 1.0 GHz signal is nontrivial, especially if you want it to
> be able to withstand 12V shocks (for when your hobbyist user
> accidentally touches the probe to the power rail while attaching the
> debugging tool).

If I have to see the signal on some dangerous high speed bus and I
don't have good gear, I usually wire up a hard drive to the mux chip
between the logic board and the servo arms.  Seagate drives have a
serial interface that lets you get into the disk's firmware and use
the disk controller's internal high speed ADC to break out the ADC
output to the test pins on the logic board.  Search for "seagate
diagnostic commands" or "alpine diagnostic commands" for the details.

Most importantly, a disk with a motor problem is usually free anyway,
so it's not a big deal if you fry it accidentally.  I'm not going to
claim it's easy or fast to set up, but sometimes it's the only
realistic option when the other two options are having a staring
contest with the schematic or getting my hands on a very expensive
high speed scope.