[squeak-dev] Raspberry - GPIO - telephone caller id - Squeak
btc at openinworld.com
Tue Jun 16 18:54:20 UTC 2015
On Tue, Jun 16, 2015 at 10:57 PM, Louis LaBrunda
<Lou at keystone-software.com> wrote:
> Hi Tim and Ben,
> To answer Tim's question, I have looked around the Raspberry Pi forums but
> the posts mostly talk about using a caller id enabled modem. Unfortunately
> the inexpensive ones don't support the latest version of caller id info
> used here in the US (I have one that doesn't work). I contacted the
> manufacturer and they have no plans to keep making the modem, never mind
> updating it to the latest caller id level.
> One of the links that one of you gave me led me to a chip the CYG2020
>  http://parts.arrow.com/item/detail/ixys/cyg2020#RpgQ that looks good for
> the job. We may also need an LCA110
>  https://parts.arrow.com/item/detail/ixys/lca110#eygg. I have ordered one
> of each for about $22.50 including tax and shipping.
> Now I need to learn enough about wiring them to a Raspberry without frying
> everything. Any help in that area will be great.
> P.S. I can point you to some PDF spec sheets if you want them.
btw also search for "application note" documents...
Where  said "Pins 13 & 14 should be connected to a 1-Form-A solid
state relay (Clare LCA110)"
confused me for a while. I had assumed that CID1 & CID2 would provide
the Caller ID Output, but it seems actually they are an input to
enable the Caller ID Output to appear on LINE1 & LINE2. If you only
want to use this for caller id and not voice/data, then I think you
can just short CID1 & CID2 together to permanently enable this mode.
In case its new to you, read about "Form 1A" contacts here
You might find this generally interesting for its layout guidelines
also page 3 here which says "This is by far the most cost effective
way to implement the Caller ID path"...
and some FCC requirements/protections...
The zeners across LINE1 & LINE 2 are said to limit voltage to Min =
-5V & Max = +5V per
page 3 of  "Transient Voltage Protection on Line 1 and Line 2 (Pins 1,2)".
This is signal not compatible with the RPi's 3.3V GPIO pins. You'd
need to use an interface circuit, maybe like the voltage divider
described at . Probably one of LINE 1 or 2 would be tied to RPi's
ground but I'm not sure if the -5 to +5 volt zener clamping means you
end up with 5V or 10V that needs to be converted to 3.3V.
Alternatively you might use an OpAmp like bottom half of Figure 5 of
Another option may be to use a 3.3V compatible device like this "Phone
or alternatively the MX602 where it looks like RXD may be a dedicated
pin for the caller id and anyway this has some interesting timing
btw, Probably the RPi forums are a better place to discuss electrical
More information about the Squeak-dev