3eddb1c300
* feat: add installer script, revise methodology * feat: update installer.sh script to fix issues * fix: re-name service to .template * fix: line endings, script update, guestbook output_file mod * fix: lambda revision * fix: add NC/NO logic for hook_type
255 lines
22 KiB
Markdown
255 lines
22 KiB
Markdown
# Rotary Phone Audio Guestbook
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- [Rotary Phone Audio Guestbook](#rotary-phone-audio-guestbook)
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- [Background](#background)
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- [Post-Event](#post-event)
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- [Future Work (Action Items)](#future-work-action-items)
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- [Materials](#materials)
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- [Hardware](#hardware)
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- [Wiring](#wiring)
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- [Hook](#hook)
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- [Phone Cord](#phone-cord)
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- [Microphone Replacement (Optional)](#microphone-replacement-optional)
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- [Software](#software)
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- [Dev Environment](#dev-environment)
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- [Installation](#installation)
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- [audioGuestBook systemctl service](#audioguestbook-systemctl-service)
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- [Config](#config)
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- [AudioInterface Class](#audiointerface-class)
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- [Operation Mode 1: audioGuestBook](#operation-mode-1-audioguestbook)
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- [Operation Mode 2: audioGuestBookwithRotaryDialer](#operation-mode-2-audioguestbookwithrotarydialer)
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- [Troubleshooting](#troubleshooting)
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- [Configuring Hook Type](#configuring-hook-type)
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- [Verify default audio interface](#verify-default-audio-interface)
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- [Check the Sound Card Configuration](#check-the-sound-card-configuration)
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- [Set the Default Sound Card](#set-the-default-sound-card)
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- [Restart ALSA](#restart-alsa)
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- [Support](#support)
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This project transforms a rotary phone into a voice recorder for use at special events (i.e. wedding audio guestbook, etc.).
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## Background
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I was inspired by my own upcoming wedding to put together a DIY solution for an audio guestbook using a rotary phone. Most online rentals were charging $600 for an experience that didn't even offer the ability to add a custom voice mail and took about 4-6 weeks of turn around time to process the audio after the event. I tried to use as many parts that I had laying around to keep costs down. It worked out quite well and we were able to gather some very special voice messages.
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Below you will find a parts list and detailed setup guide. Please feel free to reach out to me with any questions.
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## Post-Event
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Since this was a trial by fire type of scenario there ended up being a few gotchas at the real event which I've since accounted for. Namely setting a time limit on the recording length as we had some youngsters leaving 5+ minute messages repeatedly and this ended up draining the battery. Alternatively, depending on your scenario, it might be preferable to attach directly to a 5V power supply.
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### Future Work (Action Items)
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A few weeks before the wedding I had the code registering dialed numbers from the rotary encoder with the goal of playing back special messages for certain guests who dialed a certain combination (i.e. dial an area code to hear a special message to my old roomates). The details of this operation mode are described in [Mode 2](#operation-mode-2-audioguestbookwithrotarydialer) below. In order to activate this mode I had to wait for input when the phone was off the hook. This required an extra step of dialing zero before leaving a normal voice message. In the end we decided to keep it simple and I've thus migrated this code to the dev branch along with the code to run through post-porcessing the audio in a separate process.
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If any one is interested in expanding this please feel free.
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I would also like to thread the audio playback so I can have a monitor/watchdog service terminate the thread upon hook callback so that the message doesn't continue playing once the user hangs up.
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## Materials
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| Part | Notes | Quantity | Cost |
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| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- | ------------ |
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| [rotary phone](https://www.ebay.com/b/Rotary-Dial-Telephone/38038/bn_55192308) | Estate/garage/yard sales are probably the best places to find once of these. Ideally one with a phone jack since we will be using these four wires extensively. | 1 | $0.00-$60.00 |
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| [raspberry pi zero](https://www.raspberrypi.com/products/raspberry-pi-zero/) | I didn't realize how hard these are to find these days. You can use any rpi or arduino style single-board computer but be aware of size constraints (i.e. must fit inside the rotary phone enclosure) | 1 | $9.99 |
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| [raspberry pi zero case](https://www.adafruit.com/product/3252) | Optional: added for protection. One of the cases on Amazon has a heat-sink cutout which might be nice for better heat dissapation since it will all be enclosed in the end. | 1 | $4.95 |
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| [micro SD card](https://a.co/d/1gb2zhC) | Any high capacity/throughput micro SD card that is rpi compatible | 1 | $8.99 |
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| [USB Audio Adapter](https://www.adafruit.com/product/1475) | Note: I removed the external plastic shell and directly soldered the wires instead of using the female 3.5mm receptacle. | 1 | $4.95 |
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| [USB OTG Host Cable - MicroB OTG male to A female](https://www.adafruit.com/product/1099) | | 1 | $2.50 |
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| --- | **--- If you don't want to solder anything ---** | --- | --- |
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| [3.5mm Male to Screw Terminal Connector](https://www.parts-express.com/3.5mm-Male-to-Screw-Terminal-Connector-090-110?quantity=1&utm_source=google&utm_medium=cpc&utm_campaign=18395892906&utm_content=145242146127&gadid=623430178298&gclid=CjwKCAiAioifBhAXEiwApzCztl7aVb18WP4hDxnlQUCHsb62oIcnduFCSCbn9LFkZovYTQdr6omb3RoCD_gQAvD_BwE) | Optional: can connect the handset cables directly to the USB audio interface via these screw terminals | 2 | $1.37 |
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| --- | **--- If running off a battery ---** | --- | --- |
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| [LiPo Battery](https://www.adafruit.com/product/2011) | Optional: maximize capacity based on what will fit within your rotary enclosure. | 1 | $12.50 |
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| [LiPo Shim](https://www.adafruit.com/product/3196) | Optional: if you plan to run this off a LiPo I would recommend something like this to interface with the rpi zero. | 1 | $9.95 |
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| [LiPo Charger](https://www.adafruit.com/product/1904) | Optional: for re-charging the LiPo. | 1 | $6.95 |
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| --- | **--- If replacing the built-it microphone ---** | --- | --- |
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| [LavMic](https://www.amazon.com/dp/B01N6P80OQ?ref=nb_sb_ss_w_as-reorder-t1_ypp_rep_k3_1_9&=&crid=15WZEWMZ17EM9&=&sprefix=saramonic) | Optional: if you'd like to replace the carbon microphone. This is an omnidirectional lavalier mic and outputs via a 3.5mm TRS | 1 | $24.95 |
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## Hardware
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### Wiring
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#### Hook
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**Understanding Hook Types:** Depending on your rotary phone model, the hook switch may be Normally Closed (NC) or Normally Open (NO). When the phone is on the hook:
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- NC: The circuit is closed (current flows).
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- NO: The circuit is open (no current).
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To accommodate either type, you'll need to update the `config.yaml` with the appropriate hook type setting.
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- Use multimeter to do a continuity check to find out which pins control the hook:
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| On-hook --> Open circuit (Value == 1) | Off-hook --> Current flowing |
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| ------------------------------------- | -------------------------------- |
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- The B screw terminal on the rotary phone is connected to the black wire which is grounded to the rpi.
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- The L2 screw terminal on the rotary phone is connected to the white wire which is connected to GPIO pin 22 on the rpi.
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- _Note: the green wire was used for the experimental rotary encoder feature identified in the [future work](#future-work-action-items) section._
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| Rotary Phone Block Terminal | Top-down view |
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| ----------------------------------- | -------------------------------------------- |
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#### Phone Cord
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- The wires from the handset cord need to be connected to the USB audio interface
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- I soldered it but you can alternatively use 2x [3.5mm Male to Screw Terminal Connector](https://www.parts-express.com/3.5mm-Male-to-Screw-Terminal-Connector-090-110?quantity=1&utm_source=google&utm_medium=cpc&utm_campaign=18395892906&utm_content=145242146127&gadid=623430178298&gclid=CjwKCAiAioifBhAXEiwApzCztl7aVb18WP4hDxnlQUCHsb62oIcnduFCSCbn9LFkZovYTQdr6omb3RoCD_gQAvD_BwE) which plug directly into the rpi.
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- _Note: The USB audio interface looks weird in the pics since I stripped the plastic shell off in order to solder directly to the mic/speaker leads_
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- Use this ALSA command from the command line to test if the mic is working on the rpi before you set up the rotary phone: `aplay -l`
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- You might have a different hardware mapping than I did, in which case you would change the `alsa_hw_mapping` in the [config.yaml](config.yaml).
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- [Here's](https://superuser.com/questions/53957/what-do-alsa-devices-like-hw0-0-mean-how-do-i-figure-out-which-to-use) a good reference to device selection.
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- You can also check [this](https://stackoverflow.com/questions/32838279/getting-list-of-audio-input-devices-in-python) from Python.
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### Microphone Replacement (Optional)
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I found the sound quality of the built-in [carbon microphone](https://en.wikipedia.org/wiki/Carbon_microphone) on the rotary phone to be quite lacking in terms of amplitude, dynamic range and overall vocal quality. I tried boosting the gain from the digital (ALSA driver) side but this introduced an incredible amount of noise as expected. I then approached this from the analog domain and tried alternative circuitry to boost the sound quality based off this [carbon-to-dynamic converter](https://www.circuits-diy.com/mic-converter-circuit/).
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Might be worth a further investigation in the future since it retains the integrity of the original rotary phone.
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My final attempt involved the introduction of some post-proceesing (see dev branch) to bandpass some of the freqs outside the speech domain and add some normalization. The processing was costly in terms of processing and power consumption/rendering time and I ultimately decided it was worth acquiring something that yielded a better capture right out the gate. Crap in, crap out - as they say in the sound recording industry.
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To replace:
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- Unscrew mouthpiece and remove the carbon mic
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- Pop out the plastic terminal housing with the two metal leads
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- Unscrew red and black wires from terminal
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- Prepare your lav mic
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- I pulled off the 3.5mm male headphone pin since it is usually coated and annoyingly difficult to solder directly on to.
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- Carefully separate the two wires from the lav mic and spiral up the surrounding copper. This will act as our ground signal.
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- Extend the green wire from the phone cord clip to the ground point of the lav mic.
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- Red to red, black to blue as per the following diagram:
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## Software
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### Dev Environment
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- rpi image: [Rasbian](https://www.raspberrypi.com/documentation/computers/getting-started.html) w/ SSH enabled
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- rpi on same network as development machine
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- Desktop IDE: vscode w/ [SSH FS extension](https://marketplace.visualstudio.com/items?itemName=Kelvin.vscode-sshfs)
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[Here's](https://jayproulx.medium.com/headless-raspberry-pi-zero-w-setup-with-ssh-and-wi-fi-8ddd8c4d2742) a great guide to get the rpi setup headless w/ SSH & WiFi dialed in.
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### Installation
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After cloning the repository, there's an installer script available to ease the setup process. This script takes care of several tasks:
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1. Install required dependencies.
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2. Replace placeholders in the service file to adapt to your project directory.
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3. Move the modified service file to the systemd directory.
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4. Create necessary directories (recordings and sounds).
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5. Grant execution permissions to the Python scripts.
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6. Reload systemd, enable, and start the service.
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To run the installer, navigate to the project directory and execute:
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```bash
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chmod +x installer.sh
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./installer.sh
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```
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### [audioGuestBook systemctl service](audioGuestBook.service)
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The provided service ensures the Python script starts on boot. The installer script will place this service file in the `/etc/systemd/system`` directory and modify paths according to your project directory.
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To manually control the service:
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```sh
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sudo systemctl enable audioGuestBook.service
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sudo systemctl start audioGuestBook.service
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```
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This service ensures smooth operation without manual intervention every time your Raspberry Pi boots up.
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### [Config](config.yaml)
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- This file allows you to customize your own set up (edit rpi pins, audio reduction, alsa mapping, etc), modify the yaml as necessary.
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- Ensure the sample rate is supported by your audio interface (default = 44100 Hz (decimal not required))
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- For GPIO mapping, refer to the wiring diagram specific to your rpi:
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- **hook_type**: Define your hook switch type here. Set it to "NC" if your phone uses a Normally Closed hook switch or "NO" for Normally Open.
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### [AudioInterface Class](audioInterface.py)
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- Utilizes pydub and pyaudio extensively.
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- Houses the main playback/record logic and has future #TODO expansion for postprocessing the audio. Would like to test on an rpi4 to see if it can handle it better for real-time applications.
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### Operation Mode 1: [audioGuestBook](/audioGuestBook.py)
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- This is the main operation mode of the device.
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- There are two callbacks in main which poll the gpio pins for the specified activity (hook depressed, hook released).
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- In the code, depending on the `hook_type` set in the `config.yaml`, the software will adapt its behavior. For NC types, hanging up the phone will trigger the `on_hook` behavior, and lifting the phone will trigger the `off_hook` behavior. The opposite will be true for NO types.
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- Once triggered the appropriate function is called.
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- On hook (depressed)
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- Nothing happens
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- Off hook (released)
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- Plays back your own welcome message located in `/sounds/voicemail.wav` followed by the beep indicating ready to record.
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- Begins recording the guests voice message.
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- Guest hangs up, recording is stopped and stored to the `/recordings/` directory.
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### Operation Mode 2: [audioGuestBookwithRotaryDialer](./todo/audioGuestBookwithRotaryDialer.py)
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**_Note_:** Untested - decided not to go this route for my own wedding
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- This mode is a special modification of the normal operation and requires a slightly different wiring connection since it accepts input from the rotary dialer.
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- The idea was to playback special messages when particular users dial a certain number combination (i.e. 909 would play back a message for certain guests who lived with the groom in that area code).
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- In this mode of operation the users will need to dial 0 on the rotary dialer in order to initiate the voicemail.
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- The rotary dialer is a bit more complex to set up, you need a pull up resistor connected between the F screw terminal and 5V on the rpi and the other end on GPIO 23. #TODO: Diagram
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## Troubleshooting
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### Configuring Hook Type
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If you find that the behaviors for hanging up and lifting the phone are reversed, it's likely that the `hook_type` in `config.yaml` is incorrectly set. Ensure that it matches your phone's hook switch type (NC or NO).
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### Verify default audio interface
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A few users had issues where audio I/O was defaulting to HDMI. To alleviate this, check the following:
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#### Check the Sound Card Configuration
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Verify the available sound devices using the following command:
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```bash
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aplay -l
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```
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_Ensure that your USB audio interface is listed and note the card and device numbers._
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#### Set the Default Sound Card
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If you want to route audio through your USB audio interface, you'll need to make it the default sound card.
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Edit the ALSA configuration file (usually located at `/etc/asound.conf` or `~/.asoundrc`) and add the following:
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```bash
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defaults.pcm.card X
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defaults.ctl.card X
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```
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_Replace X with the card number of your USB audio interface obtained from the previous step._
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#### Restart ALSA
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```bash
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sudo /etc/init.d/alsa-utils restart
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```
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## Support
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If this code helped you or if you have some feedback, I'd be thrilled to [hear about it](mailto:dillpicholas@duck.com)!
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Feel like saying thanks? You can [buy me a coffee](https://www.buymeacoffee.com/dillpicholas) ☕.
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