I/O modules

AXO-014 — IR remote link PMOD module

Catalog #14 in the AruviX output line, level L3. Both halves of an IR remote link on one module: 38 kHz demodulating receiver (RX) and 940 nm emitter (TX).

Circuit review & bench-test guide →

Components#

Every placed component, with the reason it is on the board. Extracted directly from the schematic, so this cannot drift from the design.

Signals#

Net labels used in the schematic, which are also the names the HDL top level should use.

3V3 GND IR_OUT IR_RX IR_TX IR_TX_G IR_VS LED_A LED_K

Production status#

Source: boards/io-modules/axo-014-ir

Catalog #14 in the AruviX output line (../README.md), level L3. Both halves of an IR remote link on one module: 38 kHz demodulating receiver (RX) and 940 nm emitter (TX).

Status: schematic generated, ERC clean (0/0), netlist reviewed. PCB layout not started. Not released.

What it teaches — the NEC protocol, both directions#

• Decode (nec_ir_rx core): the TSDP34138 strips the 38 kHz carrier and hands the FPGA a clean demodulated bitstream (idle high, active low). NEC framing: 9 ms AGC burst + 4.5 ms space, then 32 bits of address/~address/command/~command, each bit a 562.5 µs burst followed by a 562.5 µs (0) or 1.6875 ms (1) space. Point any TV remote at it.
• Encode (nec_ir_tx core): the FPGA generates its own 38 kHz carrier, gates it with NEC bursts, and drives the TSAL6400 — remote-control the actuator-line robot (IR-remote robot project in ../README.md).

Receiver design (verified against stock assets)#

• Interface_Optical:TSDP341xx (stock symbol), footprint OptoDevice:Vishay_MOLD-3Pin (the symbol's own default — verified present), MPN TSDP34138 (38 kHz, 940 nm, data-link grade).
• Output type check (per the catalog's open question): the stock symbol types OUT as output (push-pull), matching the TSDP341xx datasheet's push-pull driver stage — unlike TSOP parts whose active-low out relies on an internal ~30 k pull-up. No external pull-up fitted; OUT passes the standard 100 Ω series to PMOD 1.
• Supply RC: 47 Ω + 10 µF (+100 nF at the pin). The TSDP341xx datasheet application circuit recommends an R-C in Vs (47 Ω with ≥4.7 µF) to suppress supply disturbance; 10 µF is fitted as a superset. Noted in the generator header; re-verify against the datasheet at design review. The filtered IR_VS net carries its own PWR_FLAG (axs-034 pattern).

Emitter design and the current math#

3V3 → 33 Ω (0805) → TSAL6400 → AO3400A (low-side) → GND, gate 1 k from PMOD 2 with a 10 k pull-down (emitter off while the host is unconfigured).

• Peak current: I = (3.3 − V_F − I·Rds(on)) / 33 Ω with V_F(TSAL6400) ≈ 1.35 V and Rds(on)(AO3400A @ 2.5 Vgs) ≈ 30 mΩ → ≈ 57 mA peak (the catalog's "~40 mA" estimate was conservative; the real value is stated here per the compute-and-state requirement).
• Duty: 57 mA < the TSAL6400's 100 mA continuous rating, so no duty cycle can damage it. Normal NEC traffic (38 kHz at 50 % carrier duty, gated by bursts) averages < 20 mA. Drive IR_TX with the carrier, not DC — a stuck-high pin is safe but wastes ~190 mW and floods the room.
• The 33 Ω ballast is an 0805 (RC0805FR-0733RL): I²R ≈ 107 mW peak exceeds an 0603's 100 mW DC rating.
• Emitter footprint: stock LED_THT:LED_D5.0mm_IRBlack, MPN Vishay TSAL6400 (5 mm, 940 nm).

PMOD pin map (Type 1 GPIO)#

Regenerate#

python3 generate_design.py

Remaining for release#

• [ ] PCB layout (RX shaded from the TX LED's side lobe; both at the board edge), DRC, fab outputs
• [ ] hdl/: nec_ir_rx / nec_ir_tx cores + loopback testbench
• [ ] Datasheet re-verify: TSDP341xx supply-RC values and output stage
• [ ] BOM export and availability check, design-review checklist