astra/iphone-encoder-counter

A CR2450-powered MSP430 FRAM counter combines an always-on dual-channel TMR rotation sensor, pushbutton input, and ST25DV NFC tag with an integrated tuned printed antenna and I²C/GPIO interface.

Version: 1.0.3
License: unset
Stars: 0

validation/antenna-audit.json

{
  "status": "NOT RF QUALIFIED; prototype screening only",
  "coil_turns": 7,
  "trace_width_mm": 0.25,
  "trace_spacing_mm": 0.25,
  "copper_thickness_assumed_um": 35,
  "spiral_length_mm": 758.0,
  "screening_self_inductance_uH": 2.993679128840019,
  "dc_resistance_estimate_ohm": 1.4934765714285718,
  "required_total_capacitance_at_13_56MHz_pF": 46.0167173565828,
  "chip_CTUN_pF": {
    "min": 26.5,
    "typ": 28.5,
    "max": 30.5
  },
  "C9_pF": 15,
  "assumed_parasitic_pF_for_nominal_screen": 3,
  "nominal_screen_frequency_MHz": 13.48935022430368,
  "RF_feed_branches_mm": {
    "source_net_16_mst0_0": 5.713465897735586,
    "source_net_16_mst1_0": 13.342620684573621,
    "source_net_15_mst0_0": 2.574054141770662,
    "source_net_15_mst1_0": 6.288566504648259
  },
  "limitations": [
    "Model excludes feed inductance, substrate capacitance, RF proximity losses, phone metal, ferrite, magnets and reader coupling",
    "3 pF parasitic capacitance is an assumption, not a measurement",
    "Final enclosure RF tuning and same-phone read/write testing required"
  ],
  "manufacturer_references": [
    "https://www.st.com/resource/en/application_note/an2972-how-to-design-an-antenna-for-dynamic-nfc-tags-stmicroelectronics.pdf",
    "https://www.st.com/resource/en/datasheet/st25dv04kc.pdf"
  ]
}