modem

Modem atomic-capability examples

Minimal, standalone demos of each modem communication primitive, built directly on agentcall.modem.Eg25Modem. Each script does exactly one thing so you can learn and verify a single building block in isolation — before wiring them into your own app or debugging the full CallPilot service.

These are the atoms; the full application (app.py) is what you get when you compose them (auto-answer + AI agent + audio bridge + web UI).

Capabilities

Script	Capability	Needs a live call?
at_console.py	Send any raw AT command, print the reply (the lowest-level atom)	no
probe_device.py	Self-check: SIM, signal, network, voice channel, firmware	no
dial_call.py	Place an outbound call, wait for answer, hold, hang up	—
answer_call.py	Wait for RING, auto-answer (ATA), hold until the other side hangs up	—
send_sms.py	Send one SMS (Chinese auto-encoded as UCS2)	no
receive_sms.py	Listen for and print incoming SMS (+CMTI → read → decode)	no
send_dtmf.py	Send DTMF key tones for IVR navigation (AT+QVTS)	yes

Prerequisites

1. Install the package (editable), from the repo root:

   python -m venv .venv
   .venv/bin/pip install -e ".[dev]"

2. Hardware: a Quectel EC20/EG25 modem with an active SIM (voice + SMS).
3. Config: copy .env.example to .env. The examples read MODEM_PORT / MODEM_BAUD from it (same source of truth as the app).
4. macOS only — the AT port is not a native device; start the USB→PTY bridge first, in a separate terminal, and leave it running:

   .venv/bin/python scripts/ec20_usb_pty.py --map 2:/tmp/ec20-at

   Then set MODEM_PORT=/tmp/ec20-at in .env (this is the macOS default).
5. Do not run these while the main app owns the serial port. Stop the service first (e.g. launchctl stop com.agentcall.app, or just don't run app.py) — two processes cannot share the AT port. The USB bridge can stay running.

Running

From the repo root:

.venv/bin/python examples/modem/probe_device.py
.venv/bin/python examples/modem/at_console.py "AT+CSQ"
.venv/bin/python examples/modem/dial_call.py 10000 20
.venv/bin/python examples/modem/send_sms.py 10086 CXLL

answer_call.py and receive_sms.py run until you press Ctrl-C.

Safety

• dial_call.py and send_sms.py perform real telephony and may incur carrier charges. Only dial/text numbers you are authorized to contact (your own phone, a carrier service hotline such as 10000/10086, etc.).
• send_dtmf.py only does something useful during an active call — pair it with dial_call.py.

Related tools (already in scripts/)

• scripts/eg25_probe.py — broader device probe (scans all serial ports).
• scripts/uac_check.py — verify the modem's UAC sound card works both directions.
• scripts/ec20_usb_pty.py — the macOS USB→PTY bridge these examples depend on.