Electronic – arduino – Answering landline calls with an Arduino

arduinotelephone

How can I connect an Arduino to a phone line such that, when a call rings, the Arduino will 'answer' and be able to respond with (touch) tones and, if possible, 'hear' touch tones as well for 2-way communication? Is it possible to only answer on double rings?

I saw this page on a similar topic, but that does not describe answering with an Arduino.

Best Answer

The page you link to references the Cermetek CH1817-LM Direct Access Arrangement Module. It provides a simple interrupt pin for Ring Detection, while handling some of the more complex POTS interfacing. They just didn't implement it.

The rest is simple. You just need a DTMF decoder and encoder.

Actually, the page gives you everything you need, just need to adjust the code for your own use.

Alternatively, you could use some other chips. TI's TCM1520A RING DETECTOR for ring detection. Or take apart a Answering Machine or older isa/pci 56k modems. The older, the bigger the ICs and better documented.

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Electronic – arduino – 5-pole, double-throw relay

USB Micro has the following lines:

VBUS (+5v)
Data+
Data-
ID
Ground

Of these, ID is generally not carried over a cable: It is either shorted to signal ground (host device) or left open (slave device). It does not carry any data.

Both VBus and Ground can be left connected to both endpoints in the scheme, thus reducing the switching requirement to 2 lines, D+ and D-. (Another line for ID if it must be carried across, but never seen that done). This is why USB multiplexer ICs typically carry just 2 channels.

There are several USB 2.0 multiplexer ICs that would do the job, for instance Intersil ISL54200, Maxim MAX4906/4907, or Texas Instruments TS3USB221E.

A TTL-controlled bidirectional analog multiplexer/demultiplexer like the HC4053 may be less expensive but will not work for this purpose, due to data speed requirements and capacitance matching issues.

As noted by others in the comments, USB does not take kindly to endpoints being switched. The USB protocol is not a basic TTL logic connection, it involves identification of the USB device and negotiation of speed (and also current limits). Until this handshake is done, the connection is not done.

Electronic – arduino – Alternative to Arduino tone() method

There's the Melody example on the Arduino site that just uses digitalWrite to quickly toggle the I/O pins:

void playTone(int tone, int duration) {
  for (long i = 0; i < duration * 1000L; i += tone * 2) {
    digitalWrite(speakerPin, HIGH);
    delayMicroseconds(tone);
    digitalWrite(speakerPin, LOW);
    delayMicroseconds(tone);
  }
}

The main disadvantage to this over other methods such as using a timer output is that your code will be stalled while the tone is being played, and if you have background interrupt activity occuring you may end up with a few anomalies in the tone.

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Electronic – arduino – 5-pole, double-throw relay

Electronic – arduino – Alternative to Arduino tone() method

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