[Laser] serial port PDM and PWM

[Glenn Thomas]

uhhh... does anyone on here know how USB really works? I don't.

BUT...

The ten foot cable limitation is likely not a signal level issue. On 
a high speed, multiple node serial system like USB, it may be that 
there is a timing constraint that is inherent in the protocol. This 
type of limitation is found in etherNet (~100m) and 802.11 and is due 
to a sending station waiting only a small amount of time to receive 
an ack/nak before it concludes that the message wasn't received...

BTW, if what you want to do is constant transmissions via a KISS-mode 
TNC, take a look at JNOS. Frankly, I'm too lazy to look up if JNOS as 
is will do constant transmissions. However, the source code for JNOS 
is freely available to Hams for non-commercial use, so you are 
welcome to modify it so it will do whatever it is you want.

It seems like this thread is about replacing complicated soundcard PC 
software with equally complicated serial port PC software. Why not 
build a PWM modulator out of something like a pair of 555 timers? 
This way you have a (after integration at the receiver) a linear 
analog channel with significant bandwidth. If you build the same 
system with hardware that is faster than a 555, you can have a linear 
analog channel with a bandwidth that is tens of megahertz if not hundreds.

73 de Glenn wb6w


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