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Joseph Komosa edited this page Mar 20, 2026 · 1 revision

How to build the USB‑C → FTDI (UART) cable for MYND logs and CLI

MYND’s firmware can route a UART-style CLI/log stream to the USB‑C connector, but it does not present itself as a normal USB serial device. Practically, you use a 3.3V FTDI USB‑to‑UART adapter and connect it to the USB‑C connector’s USB2 data pair (D+ / D−) plus GND.

This page is only about building the cable. For the actual “how to get a prompt” procedure, see:

What you’re building (conceptually)

  • Speaker side: a USB‑C plug that goes into the MYND speaker
  • PC side: an FTDI adapter plugged into your computer (appears as a serial port)
  • Between them: wiring that connects
    • USB‑C D+ and D− ↔ FTDI RX and TX (crossed)
    • USB‑C GND ↔ FTDI GND

Important: USB‑C cables also carry VBUS (+5V). For this CLI cable you typically do not need VBUS at all. Avoid accidentally feeding 5V into any signal pin.

Parts

  • FTDI USB‑to‑UART adapter (3.3V logic)
    Example: TTL-232R-3V3 or equivalent

  • USB‑C breakout / adapter that exposes D+, D−, GND (and usually VBUS)
    This can be:

    • a small breakout PCB with labeled pins (D+, D−, GND, VBUS, CC…), or
    • a USB‑C-to-screw-terminal adapter, or
    • a sacrificial USB‑C cable you cut open (more work; see below)

    Example of the “USB‑C to terminals/breakout” style adapter (check its labeling/silkscreen for D+, D-, GND): USB C Male to 5-Pin Terminal Block Cable

  • Jumper wires / dupont leads (or solder + heatshrink)

  • Multimeter (strongly recommended)

Reference (USB2 wire color conventions and signals):

Reference (USB‑C breakout boards and what they expose):

Option A (recommended): use a USB‑C breakout/adapter (no cable cutting)

  1. Get a USB‑C breakout/adapter with labeled pins
    Look for silkscreen labels like D+, D-, GND (sometimes VBUS too).

  2. Connect GND first

    • USB‑C breakout GND → FTDI GND

  3. Connect the data pair to FTDI RX/TX

    • USB‑C D+ → FTDI RX
    • USB‑C D- → FTDI TX

  4. If there is no output in the terminal, swap D+ and D− Some devices map UART TX/RX onto D+/D- opposite of the above. If you get no prompt, try:

    • USB‑C D+ → FTDI TX
    • USB‑C D- → FTDI RX

  5. Do not connect VBUS unless you know you need it Many breakouts include CC resistors intended for “USB device / sink” behavior (see references above). For MYND’s factory CLI you typically only need GND + D+/D-.

Option B: splice an expendable USB‑C cable (cut it open)

This is the approach your original doc implied. It works, but it’s easy to get wrong because USB‑C cables can contain extra shielding and (for USB3) additional high‑speed pairs.

1) Choose the right cable

  • Prefer a USB 2.0 USB‑C cable (charge + USB2 data).
    Avoid “USB‑C 3.x SuperSpeed” cables if possible; they have more conductors and make identification harder.

2) Cut and strip

  • Decide which end you need:

    • USB‑C plug that will go into the speaker: keep this end intact.
    • The other end: this is the end you cut/terminate to reach the inner conductors.

  • Cut the cable and strip back the outer jacket carefully.

  • You’ll typically find:

    • a shield braid / foil
    • red (VBUS +5V)
    • black (GND)
    • green (D+)
    • white (D−)
    • sometimes additional wires (CC/SBU/e-marker) depending on cable

The common USB2 color scheme is red=VBUS, black=GND, green=D+, white=D−, but verify with a multimeter because cables can vary. (See the PinoutGuide reference above.)

3) Identify D+/D−/GND reliably (recommended)

  • Use a multimeter in continuity mode against the USB‑C plug pins (or against a known breakout/connector) to confirm which conductor is D+, D−, and GND.
  • Keep D+ and D− twisted together as much as possible when re‑routing them.

4) Attach the wires to your USB‑C adapter/breakout

If you’re using a USB‑C adapter that exposes terminals/pads labeled D+, D-, GND:

  • Cable GND (and shield, if present) → adapter GND
  • Cable D+ → adapter D+
  • Cable D− → adapter D−
  • Leave VBUS unconnected unless you explicitly need it

Then wire the adapter to FTDI exactly like in Option A.

5) Strain relief and insulation

  • Heatshrink every solder joint.
  • Ensure shield/drain wire cannot short to D+/D-.
  • Add strain relief so tugging the cable doesn’t rip pads/wires off.

FTDI settings and sanity checks

  • Logic level: FTDI must be 3.3V (not 5V)
  • Common ground: GND must be shared (USB‑C GND ↔ FTDI GND)
  • Terminal settings (used later when you run the CLI):
    • 115200 baud
    • 8 data bits
    • no parity
    • 1 stop bit
    • no flow control

Quick troubleshooting

  • No prompt / nothing prints:
    • swap D+ and D- ↔ TX/RX mapping (see Option A step 4)
    • verify FTDI is 3.3V
    • verify you enabled serial routing on the speaker (see CLI access guide)
    • verify you are on the correct serial port
  • Garbled text:
    • wrong baud rate (should be 115200)
    • noisy/too-long untwisted D+/D- run; shorten wiring and keep D+/D- paired

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