Uart through an audio transformer

for IrDa?

one is the idle state of a uart, making that no light saves power

-Lasse

like

d to

tems.de

Or Modified Duobinary. My recollection is not only does it get rid of DC, but it has a less low frequency content. I took a pulse modulation class from Adam Lender in the dark ages. To say he was demanding puts it kindly.

How does it look like? I've found this for Duobinary:

Looks like you'll need an additional clock signal for it or some other synchronisation, like the start/stop bit in RS232.

One question, is it a problem if your data stream is audible?

Hopefully, it's to timestamp, in a very primitive way an audio feed. The idea is to just dump N81, from the uart at a low level, say -30 or-40dBFS, and then have a little black box containing a preamp to logic levels to drive a FTDI 232/USB thing, or maybe a USB HID/ keyboard. I like the idea of using a cheapo telecom/modem transformer, because it is floating, and will take up less PCB real estate than the electronically balanced equivalent. The Etal P3181 ( from farnell etc) seems to fit the requirements

I'll try it on my canon xl1s audio channels, to see if it works, when I get my hands on a P3181

martin

A bit steep, but a nice no-hassle part. I wonder how it performs above 4KHz.

I was recently thinking about sending some data over audio channel, but above audible range. Haven't quite figured out yet how to do it without much hardware. FSK at 20+ KHz probably.

Not a problem, the data is only dumped when required. been mucking around with some irritating 8051 bugs, so I havent really got any further with this

martin