re [pcr-1000] rs-232 db-9 pinouts

[Ted Handel]

> I'm tempted to play with the Ring Indicator line...I'm not sure for what,
> (it's probalby too noisy for audio) perhaps a real S-Meter or squelch
detect.
>  Ideas?
>

Only 5 of the 9 lines are actually used by the receiver; GND, TX, RX,
CTS,and RTS.

Pin 9 (RI) is not connected to anything.
Pin 8 (CTS) can be internally jumpered to Pin 1 (DCD)
Pin 4 (DTR) can be internally jumpered to Pin 6 (DSR)

The signal strength output from the FM demodulator can be obtained on IC8,
TA31136, Pin 12, the RSSI output.  RSSI is relative signal strength
indicator.  This signal is sent to an A/D converter on the microprocessor.
The TA31136 is a Toshiba part that is commonly used in FM receivers,
cordless phones and amateur gear, including the Icom IC-207.

There is also an analog 'meter' amp that is connected to the receiver's AGC
line.  The AGC level can be found on IC1, HD6433334, pin 31, an A/D
converter input on the microprocessor.

I suspect (but don't know for sure) that the microprocessor calculates the
FM squelch threshold by comparing the digitized and normalized RSSI value to
the digital squelch setting.  In that case you'd need to set up your own
external analog comparator circuit for squelch detection.  I don't know what
kind of detection algorithm the microprocessor uses, but it's pretty crummy.
It doesn't accurately follow transitions across the threshold, thus making
high performance scanning problematic.  Using the original PCR-1000
software, you'll notice that the scanner gets exponentially flakey on weak
signals as the scan rate is increased.

Finally I'd suggest filtering and buffering any internal signal lines before
exposing them to the outside world thru the RS-232 connector, unless you
like buying PCR receivers.

You can poll the internal signal strength and squelch at any time by sending
an ASCII string to the radio:

"I0?" + <CrLf>  The radio responds with "I004" Squelch closed, "I007"
squelch open.
"I1?" + <CrLf>  The radio responds with "I1xx" where xx is the signal
strength in hex.

Use caution when polling the radio.  Rumor has it that flooding the serial
data line causes the microprocessor to gag, which in turn can cause EEPROM
corruption.  Be sure to handshake every polling request.

If you enable autoupdate by sending the radio "G301" + <CrLf> the radio will
report changes in squelch state and signal strength automatically.
Autoupdate is a good way to pick up decoded DTMF signals; "I31x" where x =
the DTMF number.

If you're into splitting hairs, the S-meter calibration data is stored in
the EEPROM so you can accurately correct the reported signal strength for
your specific radio.

HTH.

Ted Handel, WB5REA
thandel at losalamos.com

----- Original Message ----- 
From: <nt1g at comcast.net>
To: <thandel at losalamos.com>
Sent: Thursday, June 17, 2004 8:01 PM
Subject: re [pcr-1000] rs-232 db-9 pinouts


> I'm tempted to play with the Ring Indicator line...I'm not sure for what,
> (it's probalby too noisy for audio) perhaps a real S-Meter or squelch
detect.
>  Ideas?
>
> --
> Skip Flem, NT1G
>  Hull, Massachusetts
>
>
> > RS-232 DB-9 Pinouts:
> >
> > Pin    Symbol    Flow    Decription
> >
> > 1     DCD     In     Data carrier detect
> >
> > 2     RX     In     Serial data in
> >
> > 3     TX     Out     Serial data out
> >
> > 4     DTR     Out     Data terminal ready
> >
> > 5     GND          Signal ground
> >
> > 6     DSR     In     Data set ready
> >
> > 7     RTS     Out     Ready to send
> >
> > 8     CTS     In     Clear to send
> >
> > 9     RI     In     Ring indicator
> >
> >
> > The PCR-1000 manual doesn't have the pinouts.
> > To hold power on the PCR, the RTS line must be held high.  Otherwise the
PCR
> > will auto power-down in about 20 seconds.
> >
> > Ted Handel, WB5REA
> > thandel at losalamos.com
> >
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