Electrical Design
#################

Tiliqua consists of 3 PCBAs. All of these are open-hardware designs built in KiCAD and stored in separate repositories.

Block Diagram (Tiliqua R4)
--------------------------

Below is high-level picture of how all the different electrical components of Tiliqua are connected.

.. image:: /_static/tiliqua_block_diagram.svg
  :width: 800

Some connections are omitted for simplicity (example: some ex0/ex1 pins are connected to both the ECP5 and RP2040, not shown).

Pinouts and schematics
----------------------
- **Pinout information is available in 'amaranth-boards'** `format here <https://github.com/apfaudio/tiliqua/blob/main/gateware/src/tiliqua/tiliqua_platform.py>`_.
- **Schematics for all PCBAs in the wild are plotted** `to PDFs here <https://github.com/apfaudio/tiliqua/tree/main/hardware/schematics>`_.

We now follow with a summary of the core functions of each of the Tiliqua PCBAs.

Tiliqua Motherboard
-------------------

**Repository:** `tiliqua-motherboard <https://github.com/apfaudio/tiliqua/tree/main/hardware>`_

.. image:: _static/tiliqua_motherboard_without_som.jpg
  :width: 800

- Rotary encoder with button and bar graph display.
- RP2040-based JTAG debugger and UART bridge supported by `openFPGAloader`.
- Two USB ports:
    - `dbg`: USB FS for JTAG debugging.
    - `usb2`: 480Mbit/sec USB HS PHY connected to FPGA. Device, host and dual-role operation is supported on this port with a dedicated TUSB322I CC control IC and +5V VBUS switch.
- Display output for video synthesis
    - Maximum resolution 1280x720p/60Hz or 1920x1080p/30Hz.
- 2x (PMOD-compatible) expansion ports for up to 24 simultaneous audio channels.
- MIDI-In jack (TRS-A standard) with optoisolation.
- External PLL (SI5351A) for dynamic display resolution switching.
- Soft mute for pop-free bitstream switching

FPGA SoM (`soldiercrab`)
------------------------

**Repository:** `soldiercrab <https://github.com/apfaudio/soldiercrab>`_ (see README there for more detailed docs on this SoM)

.. image:: _static/soldiercrab.jpg
  :width: 800

- Lattice ECP5 (25 K) FPGA, supported by open-source FPGA toolchains
- 256 Mbit (32 MByte) HyperRAM / oSPI RAM (for long audio buffers or video framebuffers)
- 128 Mbit (16 MByte) SPI flash for user bitstreams
- High-speed USB HS PHY (ULPI)

Audio Interface (`eurorack-pmod R3.3`)
--------------------------------------

**Repository:** `eurorack-pmod <https://github.com/apfaudio/eurorack-pmod/tree/master/hardware>`_

.. image:: _static/eurorack_pmod_bare_pcba_top.jpg
  :width: 800

- 8 (4 in + 4 out) DC-coupled audio channels, 192 KHz / 24-bit sampling
- Touch and proximity sensing on all 8 audio jacks (if unused)
- PWM-controlled, user-programmable red/green LEDs on each audio channel
- Jack insertion detection on all 8 jacks
- Built-in calibration EEPROM