docs: finish write-up (#3)

README.md

@@ -1,23 +1,27 @@
 # Rotary Phone Audio Guestbook
 
-This project transforms a rotary phone into a voice recorder for use at special events (i.e. wedding audio guestbook, etc.).
-
 - [Rotary Phone Audio Guestbook](#rotary-phone-audio-guestbook)
   - [Background](#background)
   - [Post-Event](#post-event)
-    - [Future Potential](#future-potential)
+    - [Future Work (Action Items)](#future-work-action-items)
   - [Materials](#materials)
-  - [Setup](#setup)
   - [Hardware](#hardware)
     - [Wiring](#wiring)
+      - [Hook](#hook)
+      - [Phone Cord](#phone-cord)
     - [Microphone Replacement (Optional)](#microphone-replacement-optional)
   - [Software](#software)
     - [Dev Environment](#dev-environment)
     - [Dependencies](#dependencies)
+    - [Config](#config)
     - [AudioInterface Class](#audiointerface-class)
-      - [rotaryGuestBook.service](#rotaryguestbookservice)
+      - [audioGuestBook systemctl service](#audioguestbook-systemctl-service)
-      - [Operation Mode 1: rotaryGuestBook](#operation-mode-1-rotaryguestbook)
+    - [Operation Mode 1: audioGuestBook](#operation-mode-1-audioguestbook)
-      - [Operation Mode 2: rotaryGuestBookwithRotaryDialer](#operation-mode-2-rotaryguestbookwithrotarydialer)
+    - [Operation Mode 2: audioGuestBookwithRotaryDialer](#operation-mode-2-audioguestbookwithrotarydialer)
+
+This project transforms a rotary phone into a voice recorder for use at special events (i.e. wedding audio guestbook, etc.).
+
+![image](images/final_result_2.jpg)
 
 ## Background
 
@@ -27,13 +31,15 @@ Below you will find a parts list and detailed setup guide. Please feel free to r
 
 ## Post-Event
 
-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.
+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.
 
-### Future Potential
+### Future Work (Action Items)
 
-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 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.
+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-rotaryguestbookwithrotarydialer) 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.
 If any one is interested in expanding this please feel free.
 
+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.
+
 ## Materials
 
 | Part|Notes|Quantity|Cost|
@@ -44,6 +50,8 @@ If any one is interested in expanding this please feel free.
 | [micro SD card](https://a.co/d/1gb2zhC) | Any high capacity/throughput micro SD card that is rpi compatible | 1 | $8.99 |
 | [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 |
 | [USB OTG Host Cable - MicroB OTG male to A female](https://www.adafruit.com/product/1099) | | 1 | $2.50 |
+| --- | **--- If you don't want to solder anything ---** | --- | --- |
+| [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 |
 | --- | **--- If running off a battery ---** | --- | --- |
 | [LiPo Battery](https://www.adafruit.com/product/2011)| Optional: maximize capacity based on what will fit within your rotary enclosure. |1| $12.50 |
 | [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 |
@@ -51,13 +59,43 @@ If any one is interested in expanding this please feel free.
 | --- | **--- If replacing the built-it microphone ---** | --- | --- |
 | [LavMic](https://www.amazon.com/dp/B01N6P80OQ?ref=nb_sb_ss_w_as-reorder-t1_ypp_rep_k3_1_9&amp=&crid=15WZEWMZ17EM9&amp=&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 |
 
-## Setup
+## Hardware
 
-### Hardware
+### Wiring
 
-#### Wiring
+#### Hook
 
-#### Microphone Replacement (Optional)
+- Use multimeter to do a continuity check to find out which pins control the hook:
+  
+| On-hook --> Open circuit (Value == 1)  | Off-hook --> Current flowing |
+| ------------- | ------------- |
+| ![image](images/hook_test_1.jpg) | ![image](images/hook_test_2.jpg)  |
+
+- The B screw terminal on the rotary phone is connected to the black wire which is grounded to the rpi.
+- The L2 screw terminal on the rotary phone is connected to the white wire which is connected to GPIO pin 22 on the rpi.
+
+  ![image](images/pi_block_terminal_wiring.jpg)
+
+- *Note: the green wire was used for the experimental rotary encoder feature identified in the [future work](#future-work-action-items) section.*
+
+| Rotary Phone Block Terminal  | Top-down view |
+| ------------- | ------------- |
+| ![image](images/block_terminal.jpg) | ![image](images/top_view_block_terminal.jpg)  |
+  
+#### Phone Cord
+
+- The wires from the handset cord need to be connected to the USB audio interface
+  - 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.
+    - *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*
+
+![image](images/dissected_view_1.jpg)
+
+- 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`
+  - 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).
+  - [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.
+  - You can also check [this](https://stackoverflow.com/questions/32838279/getting-list-of-audio-input-devices-in-python) from Python.
+
+### Microphone Replacement (Optional)
 
 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/).
 
@@ -70,12 +108,21 @@ To replace:
 - Unscrew mouthpiece and remove the carbon mic
 - Pop out the plastic terminal housing with the two metal leads
 - Unscrew red and black wires from terminal
+- Prepare your lav mic
+  - I pulled off the 3.5mm male headphone pin since it is usually coated and annoyingly difficult to solder directly on to.
+  - Carefully separate the two wires from the lav mic and spiral up the surrounding copper. This will act as our ground signal.
+- Extend the green wire from the phone cord clip to the ground point of the lav mic.
+- Red to red, black to blue as per the following diagram:
 
-![image](images/phone2.jpg)
+![image](images/phone_wiring.jpg)
 
-### Software
+![image](images/handset_mic_wiring.jpg)
 
-#### Dev Environment
+![image](images/handset_mic_positioning.jpg)
+
+## Software
+
+### Dev Environment
 
 - rpi image: [Rasbian](https://www.raspberrypi.com/documentation/computers/getting-started.html) w/ SSH enabled
 - rpi on same network as development machine
@@ -83,7 +130,7 @@ To replace:
 
 [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.
 
-#### Dependencies
+### Dependencies
 
 - `pip3 install -r requirements.txt` or pip install each manually:
   - [GPIOZero](https://gpiozero.readthedocs.io)
@@ -91,22 +138,44 @@ To replace:
   - [PyAudio](https://people.csail.mit.edu/hubert/pyaudio/)
   - [PyYAML](https://pyyaml.org/)
 
-#### [AudioInterface Class](audioInterface.py)
+### [Config](config.yaml)
 
-#### [rotaryGuestBook.service](rotaryGuestBook.service)
+- This file allows you to customize your own set up (edit rpi pins, audio reduction, alsa mapping, etc), modify the yaml as necessary.
+
+- For GPIO mapping, refer to the wiring diagram specific to your rpi:
+  ![image](images/rpi_GPIO.png)
+
+### [AudioInterface Class](audioInterface.py)
+
+- Utilizes pydub and pyaudio extensively.
+- 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.
+
+#### [audioGuestBook systemctl service](/audioGuestBook.service)
 
 This service starts the python script on boot. Place it in the `/etc/systemd/system` directory.
 
-`systemctl enable audioGuestBook.service`
+```sh
-`systemctl start audioGuestBook.service`
+systemctl enable audioGuestBook.service
+systemctl start audioGuestBook.service
+```
 
+### Operation Mode 1: [audioGuestBook](/audioGuestBook.py)
 
-#### Operation Mode 1: [rotaryGuestBook](rotaryGuestBook.py)
+- This is the main operation mode of the device.
+- There are two callbacks in main which poll the gpio pins for the specified activity (hook depressed, hook released).
+- Once triggered the appropriate function is called.
+- On hook (depressed)
+  - Nothing happens
+- Off hook (released)
+  - Plays back your own welcome message located in `/sounds/voicemail.wav` followed by the beep indicating ready to record.
+  - Begins recording the guests voice message.
+  - Guest hangs up, recording is stopped and stored to the `/recordings/` directory.
 
-#### Operation Mode 2: [rotaryGuestBookwithRotaryDialer](rotaryGuestBookwithRotaryDialer.py)
+### Operation Mode 2: [audioGuestBookwithRotaryDialer](./todo/audioGuestBookwithRotaryDialer.py)
 
 ***Note*:** Untested - decided not to go this route for my own wedding
 
 - 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.
 - 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).
 - In this mode of operation the users will need to dial 0 on the rotary dialer in order to initiate the voicemail.
+- 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