Show page

Differences

This shows you the differences between two versions of the page.

--- pm:prj2026:bianca.popa1106:mihai.brisculescu [2026/05/27 20:45]
mihai.brisculescu [Current implementation status]
+++ pm:prj2026:bianca.popa1106:mihai.brisculescu [2026/05/28 16:17] (current)
mihai.brisculescu [4. Audio Output — Triple I2S Architecture]
@@ Line 98: / Line 98: @@
 There was **one hardware fix** I had to make during bring-up: the jack-detect lines didn't work on the first powered-up board because the UDA1334A breakout's onboard 47 µF AC-coupling capacitors leave the jack TIP nodes floating at DC, so the tip switch can't actually drag the detect line low. I fixed it by soldering a **10 kΩ resistor from each jack's TIP to its sleeve (GNDA)** on the audio side of the AC-coupling cap — that pins TIP to GNDA at DC, and the tip switch can do its job again. This isn't on the schematic; it's a point-to-point fix on the assembled board.
-{{:pm:prj2026:bianca.popa1106:pcb_top_brisculescu.png?nolink&800}}
+{{ :pm:prj2026:bianca.popa1106:pcb_top_brisculescu.png?nolink&800 }}
 ==== Schematic (full) ====
@@ Line 155: / Line 155: @@
 **Critical constraints I had to respect:**
   * All Teensy 4.0 GPIO pins are 3.3 V logic and are **NOT 5 V tolerant**. Every peripheral has been chosen accordingly.
-  * The VIN-to-VUSB copper trace on the bottom of the Teensy must be **cut** when the board is powered from an external battery, otherwise the USB rail back-feeds into the battery path. This trace IS cut on the assembled board.
+  * The VIN-to-VUSB copper trace on the bottom of the Teensy or the USB cable's red wire must be **cut** when the board is powered from an external battery, otherwise the USB rail back-feeds into the battery path.
   * Debug uses USB ''Serial'' (12 Mbit/s), so IO 0 and IO 1 — which default to ''Serial1'' RX/TX — are repurposed as GPIO outputs driving the MAX98357A ''SD_MODE'' lines. Firmware must therefore **never call ''Serial1.begin()''**.
 </note>
@@ Line 246: / Line 246: @@
 <note warning>
 **Required breakout rework:** The Adafruit 3006 breakout (and clones) includes a 1 MΩ SMD pull-up between ''SD_MODE'' and the chip's V_DD (5 V). This must be **desoldered from each breakout before installation** — otherwise the GPIO LOW state would fight the pull-up and shutdown never engages. Once removed, only the chip's internal 100 kΩ pull-down remains.
-**Do NOT bridge any breakout channel-selection solder jumpers** (''L'', ''R'', ''Mono''). If bridged, they hard-tie ''SD_MODE'' to the chip's 5 V VDD, and driving the GPIO LOW would short 5 V to GND through the 3.3 V GPIO pin and damage the Teensy.
 </note>
@@ Line 376: / Line 374: @@
 | 23 / A9 | ''JACK_GUITAR_DET'' | GPIO input | Plain digital input. 100 kΩ pull-up + RC LPF (4.7 kΩ / 1 µF). |
 | 24–33 | NC | — | Back-side pads, unused. |
-| VIN | +5V input | Power | From MT3608 (VIN-VUSB trace cut on the Teensy). |
+| VIN | +5V input | Power | From MT3608 (Teensy's VIN-VUSB trace / USB cable's red wire cut). |
 | GND | Ground | Power | Connected to ''GND'' (digital) domain. |
 | 3.3V | 3.3V output | Power | From Teensy LDO → shift registers, joystick, both pots, OLED, UDA1334A breakout, all pull-ups, battery-sense divider. |
-==== Photos / proof-of-life ====
+==== Photos ====
-[[https://youtu.be/l58ewZxxkRw|Mini Synth Demo]]
+{{ :pm:prj2026:bianca.popa1106:img_4742.jpg?nolink&800 }}
-{{ :pm:prj2026:bianca.popa1106:img_4738.jpg?nolink&600 |}}
+{{ :pm:prj2026:bianca.popa1106:img_4744.jpeg?nolink&800 }}
-{{ :pm:prj2026:bianca.popa1106:img_4742.jpg?nolink&600 |}}
+{{ :pm:prj2026:bianca.popa1106:img_4746.jpeg?nolink&800 }}
-{{ :pm:prj2026:bianca.popa1106:img_4837.jpg?nolink&600 |}}
+{{ :pm:prj2026:bianca.popa1106:img_4838.jpg?nolink&800 }}
-{{ :pm:prj2026:bianca.popa1106:img_4838.jpg?nolink&600 |}}
 ==== Hardware milestones ====
@@ Line 476: / Line 473: @@
 <code>
-IDLE ─trigger─▶ ARMED ──count-in──▶ RECORDING ─trigger─▶ PLAYING
+IDLE ─trigger─▶ ARMED ─count-in─▶ RECORDING ─trigger─▶ PLAYING
-                                                            │
+                                                          │ ▲
-                                       ┌──trigger──┐        │
+                                                          │ │ trigger
-                                       │           ▼        │
+                                                  trigger │ │
-                              ARMED_OVERDUB ── wrap ──▶  OVERDUB ┘
+                                                          ▼ │
+                                                   ARMED_OVERDUB
+                                                          │
+                                                         wrap
+                                                          ▼
+                                                       OVERDUB
-   long-hold trigger from PLAYING / OVERDUB ─▶  END_PROMPT (Save / Clear / Cancel)
+PLAYING / OVERDUB ─long-hold trigger─▶ END_PROMPT
+                                      Save / Clear / Cancel
 </code>
@@ Line 652: / Line 655: @@
   * **Reset defaults test.** Settings → Reset → Reset. Confirm voice count = 8, concert pitch = 440 Hz, scale = Chromatic, all effects off, sine waveform selected. Confirm BPM / metronome / metronome volume are **NOT** reset (the looper EEPROM blob is intentionally preserved).
-==== Demo video ====
+==== Demo videos ====
-<note tip>
+[[https://youtu.be/l58ewZxxkRw|Mini Synth Demo]]
-A demo video covering: boot splash, playing a few notes on each instrument category, sweeping the FX pot, recording + overdubbing a loop, saving it to SD, plugging in headphones and confirming the speakers mute — will be uploaded here before the final deadline.
-</note>
+[[https://youtu.be/we-T9mZoAho|Mini Synth - Aria Math Demo]]
+[[https://youtu.be/KdVtQQpLlJo|Mini Synth - Moog City 3 Demo]]
 ===== Results =====
@@ Line 688: / Line 692: @@
   * Hardware bring-up problem-solving — the jack-detect issue with the AC-coupled UDA1334A outputs was a real "oh no, the board doesn't work" moment that turned into a clean 10 kΩ-per-jack fix once I traced it.
-If I were to do it again, I'd probably move the metronome's audio path into a dedicated I2S channel rather than ''master.port1'' so the click is even more obviously separated from the looper record bus. And I'd add a real Concert-Pitch fine-tuner (cents) on top of the existing 1 Hz step. But for a one-semester project I'm pretty happy with where it landed.
+If I were to do it again, I’d do better PCB routing, use discrete components instead of daughter boards, go with SMD instead of THT, make the PCB easy to install in a 3D printed enclosure, design an enclosure, add velocity sensitive keys, add better power management, use SDIO instead of SPI for SD card communication, find a way to record longer loops, maybe using a different type of memory. I'd also probably move the metronome's audio path into a dedicated I2S channel rather than ''master.port1'' so the click is even more obviously separated from the looper record bus. And I'd add a real Concert-Pitch fine-tuner (cents) on top of the existing 1 Hz step. But for a one-semester project I'm pretty happy with where it landed.
 ===== Download =====
@@ Line 699: / Line 703: @@
 </note>
-  * Full schematic: {{:pm:prj2026:bianca.popa1106:minisynth_brisculescu.pdf|minisynth_brisculescu.pdf}}
+  * Firmware source code: [[https://github.com/MidsoftEntertainment/MiniSynth-public|MiniSynth Public Repo]]
+  * Full schematic: {{:pm:prj2026:bianca.popa1106:minisynth_brisculescu.pdf|MiniSynth.pdf}}
+  * Example loop: {{:pm:prj2026:bianca.popa1106:loop_002.wav|LOOP_002.WAV}}
 ===== Journal =====