Accordion Beacon Module
ESH10000671 · Rev R0
Generated 2026-06-05 18:18 UTC
Battery-powered WiFi module that extends a Raspberry Pi's serial bus (I2C, UART, SPI) over WiFi using MQTT. SX1276 LoRa 868 MHz transceiver supplements WiFi for long-range parallel operation. LiPo powered with USB-C charging (BQ24075), 3.3V LDO (MCP1700), ESP32-C6-MINI-1-N4 MCU.
Coverage
100%
Done
0%
Requirements
59
Test Cases
34
Records
0
Requirements
| Code | Status | Category | Title | Statement | Acceptance |
|---|---|---|---|---|---|
| REQ-001 | approved | Functional | Charge LiPo battery via USB-C | The module shall charge a single-cell LiPo battery via USB-C connector | Battery charges from USB-C 5V source; charge current observed |
| REQ-002 | approved | Interface | BQ24075 charge IC with power path management | The charge IC shall be BQ24075 (or compatible) with integrated power path management | Correct IC placed; SYS pin powers system from VBUS when connected |
| REQ-003 | approved | Performance | Charge current ~593 mA (ISET 1.5 kΩ) | The charge current shall be approximately 593 mA (ISET resistor = 1.5 kΩ, same value as ILIM) | Measured charge current ≤ 650 mA; may be reduced by BQ24075 TREG thermal throttling |
| REQ-004 | approved | Functional | Charge status indicators via CHG and PG outputs | Charge status indicators shall be provided via CHG (charging) and PG (power good) outputs | CHG LED on during charge; PG LED on when VBUS present |
| REQ-005 | approved | Mechanical | JST-PH 2.0mm 2-pin battery connector | The battery shall connect via a JST-PH 2.0 mm 2-pin connector. | JST-PH 2.0 mm connector fitted; battery pack with matching plug mates correctly. |
| REQ-006 | approved | Functional | 3.3V rail from BQ24075 SYS pin | The 3.3V power rail shall be derived from the BQ24075 SYS pin via an LDO regulator. | 3.3V rail measures within ±2% under all load conditions when powered from BQ24075 SYS output. |
| REQ-007 | approved | Interface | MCP1700-3302E/TO LDO regulator | The LDO regulator shall be the MCP1700-3302E/TO device. | MCP1700-3302E/TO is populated and provides a stable 3.3V output as per datasheet specifications. |
| REQ-008 | approved | Performance | LDO quiescent current ≤ 4 µA | The LDO regulator quiescent current shall not exceed 4 µA. | Measured quiescent current of MCP1700 is ≤ 4 µA under no-load condition. |
| REQ-009 | approved | Interface | 3.3V rail bulk decoupling capacitors | The 3.3V rail shall have bulk decoupling: 100 µF tantalum/electrolytic, 10 µF MLCC, 100 nF MLCC | All three capacitors present; placed close to ESP32 module |
| REQ-010 | approved | Interface | LDO input and output decoupling | The LDO input shall have 1 µF decoupling and the output shall have 1 µF decoupling (per MCP1700 datasheet) | Capacitors present per datasheet recommendation |
| REQ-011 | approved | Functional | Battery voltage monitoring via ADS7828 CH0 | The module shall monitor battery voltage via the ADS7828 ADC (CH0) through a resistor divider | Battery voltage readable via ADS7828 CH0 over I2C |
| REQ-012 | approved | Performance | Battery divider 2×1 MΩ (1:2 ratio) | The resistor divider shall use 2 × 1 MΩ resistors (1:2 ratio, max 2.1V to ADC input) | Divider output ≤ 2.1V when battery at 4.2V |
| REQ-013 | approved | Performance | Battery divider quiescent drain ≤ 5 µA | The divider quiescent drain shall not exceed 5 µA at full charge | Calculated: 4.2V / 2MΩ = 2.1 µA — accepted as within deep sleep budget |
| REQ-014 | approved | Performance | Battery divider software-disconnectable | The divider shall be software-disconnectable (GPIO-driven low-side) to eliminate drain during deep sleep | Divider drain accepted at 2.1 µA (within budget); no switch fitted R0 |
| REQ-015 | approved | Interface | MCU module ESP32-C6-MINI-1-N4 | The MCU module shall be ESP32-C6-MINI-1-N4 (4 MB flash, PCB antenna) | Correct module placed; boots and responds to programming |
| REQ-016 | approved | Performance | MCU supply voltage 3.0–3.6V | The MCU supply voltage shall be 3.0–3.6V (from 3.3V rail) | VCC measured within 3.0–3.6V range |
| REQ-017 | approved | Performance | Deep sleep total board current ≤ 20 µA | The module shall support deep sleep with total board current consumption ≤ 20 µA (ESP32 + LDO + GPIO expander + ADC power-down + divider off). | Total board current in deep sleep ≤ 20 µA |
| REQ-018 | approved | Functional | WiFi 802.11ax (WiFi 6) at 2.4 GHz | The module shall support WiFi 802.11ax (WiFi 6) at 2.4 GHz. | WiFi connection established at 2.4 GHz |
| REQ-019 | approved | Functional | BLE 5.0 support | The module shall support BLE 5.0 | BLE advertisement/connection established |
| REQ-020 | approved | Interface | I2C bus on external connector | The module shall expose I2C bus signals (SDA, SCL) on an external connector | I2C device detected and communicates through module |
| REQ-021 | approved | Interface | UART on external connector | The module shall expose UART signals (TX, RX) on an external connector | UART loopback or communication verified |
| REQ-022 | approved | Interface | SPI bus on external connector | The module shall expose SPI bus signals (MOSI, MISO, SCK, CS) on an external connector | SPI device communicates through module |
| REQ-023 | approved | Interface | Serial bus connector 3.3V and GND | The serial bus connector shall provide 3.3V and GND for external sensor power | 3.3V and GND present on connector |
| REQ-024 | approved | Mechanical | USB-C connector for charging | The module shall have a USB-C connector for charging | USB-C cable connects; VBUS voltage present at charge IC |
| REQ-025 | approved | Safety | USB-C VBUS ESD protection | The USB-C VBUS line shall have ESD protection | ESD protection diode present on VBUS |
| REQ-026 | approved | Mechanical | ESP32 antenna keep-out zone observed | The PCB shall observe the ESP32-C6-MINI-1 antenna keep-out zone (no copper under PCB antenna area) | No copper pour or traces in antenna keep-out zone |
| REQ-027 | approved | Mechanical | 100 nF decoupling caps near ESP32 VCC pads | 100 nF decoupling caps shall be placed as close as possible to ESP32 VCC pads | Visual inspection: cap placement ≤ 3 mm from VCC pad |
| REQ-028 | approved | Mechanical | Bulk 100 µF cap near ESP32 module | Bulk 100 µF cap shall be placed near ESP32 module, not near LDO output | Visual inspection confirms placement |
| REQ-029 | approved | Mechanical | Battery monitor divider routed away from RF | Battery monitor divider shall be routed away from RF section | Visual inspection; no interference observed |
| REQ-030 | approved | Mechanical | Test points on 3.3V, GND, UART TX/RX, BOOT, RESET | Test points shall be provided on: 3.3V rail, GND, UART TX, UART RX, BOOT, RESET | All 6 test points present and accessible |
| REQ-031 | approved | Functional | WiFi MQTT communication with Raspberry Pi | The module shall communicate with the Raspberry Pi master over WiFi (protocol TBD — MQTT candidate) | Wireless message sent and received by RPi |
| REQ-032 | approved | Functional | Configurable sleep interval persisted in NVS | The module shall support configurable sleep interval (persisted in NVS flash) | Sleep interval changed via MQTT command; persists across power cycles |
| REQ-033 | approved | Functional | Sleep OFF and Sleep ON operating modes | The module shall support two operating modes: Sleep OFF (WiFi always on) and Sleep ON (deep sleep with wake interval) | Both modes functional and selectable via MQTT command |
| REQ-034 | approved | Performance | Static IP, wake-to-TX ≤ 500 ms | The module shall use static IP with WiFi credentials stored in RTC memory to minimize wake-to-TX time | Wake-to-MQTT-publish time ≤ 500 ms with static IP |
| REQ-035 | approved | Performance | ≥ 7 days runtime at 10 s wake interval | The module shall achieve ≥ 7 days runtime on 800 mAh LiPo at 10 s wake interval | Measured or validated average current ≤ 4.8 mA |
| REQ-036 | approved | Performance | ≥ 45 days runtime at 30 s wake interval | The module shall achieve ≥ 45 days runtime on 800 mAh LiPo at 30 s wake interval | Measured or validated average current ≤ 0.75 mA |
| REQ-037 | approved | Interface | PI4IOE5V6416 I2C GPIO expander | The module shall include a PI4IOE5V6416 I2C GPIO expander on the on-board LP_I2C bus | IC responds to I2C address; GPIOs readable/writable |
| REQ-038 | approved | Functional | GPIO expander external module control signals | The GPIO expander shall provide the following external module control signals on the connector: SHDNn, RESETn, INTERRUPTn, SRQn, ALERTn, EVENTn | All 6 signals present on connector; toggleable via I2C |
| REQ-039 | approved | Functional | GPIO expander INT to IO22 for wake-from-sleep | The GPIO expander INT output shall be connected to ESP32-C6 GPIO IO22 via net GPIO_INTn to enable wake-from-deep-sleep on any expander input change | ESP32 wakes from deep sleep when expander input state changes |
| REQ-040 | approved | Interface | GPIO expander 3.3V with 100 nF decoupling | The GPIO expander shall operate on the 3.3V rail with 100 nF decoupling | VCC measured 3.3V ± 3%; decoupling cap present |
| REQ-041 | approved | Interface | ADS7828 12-bit 8-channel I2C ADC | The module shall include an ADS7828 12-bit 8-channel I2C ADC on the on-board LP_I2C bus | IC responds to I2C address; ADC channels readable |
| REQ-042 | approved | Functional | ADC CH0 battery voltage monitoring | ADC channel 0 shall monitor battery voltage via a 2×1 MΩ resistor divider (1:2, max 2.1V at 4.2V battery) | Battery voltage readable; divider output within 2% of expected |
| REQ-043 | approved | Functional | Remaining ADC channels available | Remaining ADC channels (1–7) shall be available for system monitoring or exposed on the external connector | Spare channels accessible and functional |
| REQ-045 | approved | Interface | ADS7828 3.3V decoupling and VREF from REF3425 | The ADS7828 shall operate on the 3.3V rail with 100 nF decoupling; VREF connected to REF3425 2.5V output (REQ-058) | VCC measured 3.3V ± 3%; VREF measured 2.5V ± 0.05%; decoupling cap present |
| REQ-046 | approved | Functional | Operate from USB alone | The module shall operate from USB power alone, with no battery connected. | Module powers on and operates normally with USB-C connected and no battery present. |
| REQ-047 | approved | Functional | Prioritise USB over battery when USB connected | When USB is connected, the power path management shall prioritise USB over battery, supplying the system from VBUS and simultaneously charging the battery. | With USB and battery both connected, system load is sourced from USB; battery charge current flows simultaneously. |
| REQ-048 | approved | Functional | Simultaneous charging and system operation | The design shall support simultaneous battery charging and full system operation without interruption. | System operates without reset or brown-out while battery is charging from USB. |
| REQ-049 | approved | Interface | BOOT pin USB bootloader access | The BOOT pin (IO9) shall allow entry into USB bootloader mode by pulling low during reset; access via the IO9-side pad of the I2C0 SCL pull-up resistor | ESP32 enters bootloader when IO9 pulled low at power-on; normal boot when released |
| REQ-050 | approved | Functional | SX1276 LoRa 868 MHz transceiver | The module shall include an SX1276 LoRa transceiver operating at 868 MHz (EU ISM band) as a supplement to the WiFi interface | SX1276 responds to SPI commands; LoRa packet transmitted and received at 868 MHz |
| REQ-051 | approved | Interface | SX1276 on SPI2 with IO4 NSS | The SX1276 shall share the SPI2 bus (IO18–21) with a dedicated NSS line on IO4 (net CS0) | SPI2 communicates with SX1276 when IO4 asserted low; external SPI device unaffected |
| REQ-052 | approved | Interface | SX1276 DIO0 interrupt on IO5 | The SX1276 DIO0 interrupt output shall be connected to IO5 (net LORA_INTn) to enable interrupt-driven TX/RX completion handling | IRQ received on IO5 on TxDone and RxDone events |
| REQ-053 | approved | Interface | SX1276 RESET via GPIO expander | The SX1276 RESET pin shall be driven by a PI4IOE5V6416 GPIO expander output; firmware shall initialise the expander before asserting LoRa RESET | SX1276 RESET assertable via I2C to GPIO expander; firmware sequencing constraint documented |
| REQ-054 | approved | Interface | SX1276 SMA connector 50 Ω matched trace | The SX1276 RF output shall be connected to an SMA connector via a 50 Ω matched trace | SMA connector present; trace impedance 50 Ω ±10% by design |
| REQ-055 | approved | Mechanical | SX1276 RF positioned away from ESP32 antenna | The SX1276 RF section and SMA connector shall be positioned to minimise RF interference with the ESP32-C6-MINI-1 2.4 GHz PCB antenna | LoRa RF components placed away from ESP32 antenna keep-out zone; no WiFi link failure during concurrent LoRa TX |
| REQ-056 | approved | Performance | SX1276 sleep mode during ESP32 deep sleep | The SX1276 shall enter sleep mode during ESP32 deep sleep; its sleep current shall remain within the REQ-017 total board budget | Total board deep sleep current ≤ 20 µA including SX1276 (SX1276 sleep typ. 0.2 µA) |
| REQ-057 | approved | Functional | LoRa and WiFi concurrent operation | LoRa and WiFi shall be capable of concurrent operation; neither interface shall be a fallback replacement for the other | WiFi connection maintained while LoRa transmits/receives; no mutual interference causing link failure |
| REQ-058 | approved | Interface | REF3425 2.5V precision voltage reference | The module shall include a REF3425 2.5V precision voltage reference on the Power sheet to supply VREF to the ADS7828 ADC | REF3425 output measured 2.5V ± 0.05%; ADS7828 VREF connected to REF3425 output |
| REQ-059 | approved | Functional | Bidirectional battery current measurement via INA333 | The module shall measure bidirectional battery current via a 100 mΩ shunt resistor and INA333 instrumentation amplifier (gain ≈ 20.6) into ADS7828 CH1; resolution ≤ 1 mA; range ±600 mA | Battery current readable via ADS7828 CH1; 0 A reads mid-scale (≈ code 2048); ±600 mA within ADC range |
| REQ-060 | approved | Performance | INA333 power-gated during deep sleep | The INA333 shall be power-gated via AO3407 PMOS switch controlled by PI4IOE P11 (SHUNTn, active-low) to eliminate quiescent current during deep sleep | INA333 draws 0 µA when P11 = HIGH; powers up when P11 = LOW; deep sleep budget unaffected |
| REQ-061 | draft | Functional | BOM review before production release | Before transitioning R0 to production, the BOM shall be reviewed and updated to cost-effective alternatives where available | BOM review completed; cost-effective parts substituted or prototype parts confirmed; review record in DECISIONS.md |
Test Cases
| Code | Status | Category | Title / Signal | Target | Pass Criterion | Linked REQ |
|---|---|---|---|---|---|---|
| TC-A-00 | open | functional | ADC_GPIO | 2.1 ± 2% | Divider output measures 2.10V ± 2% with VBAT=4.2V | REQ-011 |
| TC-A-01 | open | functional | ADC_GPIO | 1.5 ± 2% | Divider output measures 1.50V ± 2% with VBAT=3.0V | REQ-011 |
| TC-A-02 | open | functional | ADC_GPIO | 0 | No measurable current through divider when GPIO driven low in deep sleep | REQ-013 |
| TC-A-03 | open | functional | VBAT | 10 | Total board current ≤ 20 µA in deep sleep with divider off at VBAT=3.7V | REQ-056 |
| TC-A-04 | open | functional | VREF | 2.5 ± 0.05% | REF3425 output measures 2.500V ± 0.05% at VREF net (ADS7828 VREF pin) | REQ-058 |
| TC-B-00 | open | functional | BOM cost and production readiness review | — | BOM review completed; cost-effective alternatives evaluated; prototype-only parts substituted or confirmed; review record captured in DECISIONS.md | REQ-061 |
| TC-C-00 | open | functional | USB-C connector fit | — | USB-C cable inserts and locks correctly; VBUS present | REQ-024 |
| TC-C-01 | open | functional | JST-PH battery connector fit and polarity | — | JST-PH 2-pin battery cable inserts correctly; polarity correct; battery charges | REQ-005 |
| TC-C-02 | open | functional | 3V3 | 3.3 ± 3% | Connector pinout matches schematic; 3.3V measures 3.30V ± 3% on connector | REQ-023 |
| TC-C-03 | open | Safety | USB-C VBUS ESD protection | — | ESD protection diode present and functional on VBUS line; no damage after USB connection | REQ-025 |
| TC-D-00 | open | functional | ESP32 boot and UART output | — | ESP32 programmed successfully; serial output visible on UART0 after boot | REQ-016 |
| TC-D-01 | open | functional | I2C scan — external connector | — | I2C device detected at expected address via external connector | REQ-020 |
| TC-D-02 | open | functional | UART loopback — external connector | — | Known data sent and received correctly through external UART connector at 115200 baud | REQ-021 |
| TC-D-03 | open | functional | SPI loopback — external connector | — | SPI device read/write verified through external SPI connector | REQ-022 |
| TC-L-00 | open | functional | SX1276 SPI comms and register read | — | SX1276 responds to SPI read of register 0x42 (VERSION) with 0x12; chip selectable via IO4 NSS | REQ-050 |
| TC-L-01 | open | functional | SX1276 DIO0 interrupt routing | — | DIO0 rising edge triggers interrupt on ESP32 IO5 within 1 ms of TX-done or RX-done event | REQ-052 |
| TC-L-02 | open | functional | LoRa and WiFi concurrent operation | — | Device maintains WiFi association while transmitting LoRa packet; no packet loss or disconnection observed | REQ-057 |
| TC-M-00 | open | Mechanical | Visual inspection | — | No manufacturing defects, solder quality acceptable, all components correctly placed | REQ-009 |
| TC-M-01 | open | Mechanical | Antenna keep-out zone | — | No copper pour or traces under ESP32-C6-MINI-1 antenna area per datasheet keep-out zone | REQ-026 |
| TC-M-02 | open | Mechanical | VCC | 3 | 100 nF decoupling cap within 3 mm of ESP32 VCC pads | REQ-027 |
| TC-M-03 | open | Mechanical | Test point access verification | — | All 6 test points present and accessible: 3.3V, GND, UART TX, UART RX, BOOT, RESET | REQ-030 |
| TC-P-00 | open | functional | VBUS | 5 ± 5% | VBUS measures 5.0V ± 0.25V at charge IC input when USB-C 5V source connected | REQ-024 |
| TC-P-01 | open | functional | VBAT | 593 ± 10% | Charge current ≤ 650 mA during CC phase with USB-C 5V and LiPo connected | REQ-003 |
| TC-P-02 | open | functional | Charge status LED | — | CHG LED on during charge; PG LED on when VBUS present | REQ-004 |
| TC-P-03 | open | functional | 3V3 | 3.3 ± 3% | 3.3V rail measures within ±3% at no load with VBAT=4.2V | REQ-006 |
| TC-P-04 | open | functional | 3V3 | 3.3 ± 3% | 3.3V rail measures within ±3% at no load with VBAT=3.0V | REQ-006 |
| TC-P-05 | open | functional | 3V3 | 3.3 ± 5% | 3.3V rail within ±5% with ESP32 in active WiFi TX mode at VBAT=3.7V | REQ-006 |
| TC-P-06 | open | functional | LDO_IN | 4 | LDO input current ≤ 4 µA with ESP32 in deep sleep and no load at VBAT=3.7V | REQ-008 |
| TC-S-00 | open | functional | WiFi connection at 2.4 GHz | — | ESP32 connects to WiFi AP at 2.4 GHz; IP address assigned or static IP in use | REQ-031 |
| TC-S-01 | open | functional | BLE 5.0 advertisement | — | BLE advertising started; visible from phone/BLE scanner nearby | REQ-019 |
| TC-S-02 | open | functional | MQTT publish to Raspberry Pi broker | — | Module wakes, connects to WiFi, publishes MQTT message; message received on RPi broker | REQ-031 |
| TC-S-03 | open | functional | Sleep mode toggle via MQTT | — | Both Sleep OFF and Sleep ON modes functional and switchable via MQTT command | REQ-033 |
| TC-S-04 | open | performance | wake_to_tx | 500 | Time from deep sleep wake to MQTT publish ≤ 500 ms with static IP configuration | REQ-034 |
| TC-S-05 | open | performance | VBAT | 4.8 | Average current ≤ 4.8 mA at 10 s wake interval over 10-minute measurement window at VBAT=3.7V | REQ-035 |
Coverage Matrix
| REQ | Title | Category | Coverage | Linked Test Cases |
|---|---|---|---|---|
| REQ-001 | Charge LiPo battery via USB-C | Functional | approved | TC-P-01, TC-P-02 |
| REQ-002 | BQ24075 charge IC with power path management | Interface | approved | TC-P-01, TC-P-02 |
| REQ-003 | Charge current ~593 mA (ISET 1.5 kΩ) | Performance | approved | TC-P-01 |
| REQ-004 | Charge status indicators via CHG and PG outputs | Functional | approved | TC-P-02 |
| REQ-005 | JST-PH 2.0mm 2-pin battery connector | Mechanical | approved | TC-C-01 |
| REQ-006 | 3.3V rail from BQ24075 SYS pin | Functional | approved | TC-P-03, TC-P-04, TC-P-05 |
| REQ-007 | MCP1700-3302E/TO LDO regulator | Interface | approved | TC-P-03 |
| REQ-008 | LDO quiescent current ≤ 4 µA | Performance | approved | TC-P-06 |
| REQ-009 | 3.3V rail bulk decoupling capacitors | Interface | approved | TC-M-00, TC-M-02 |
| REQ-010 | LDO input and output decoupling | Interface | approved | TC-M-00 |
| REQ-011 | Battery voltage monitoring via ADS7828 CH0 | Functional | approved | TC-A-00, TC-A-01 |
| REQ-012 | Battery divider 2×1 MΩ (1:2 ratio) | Performance | approved | TC-A-00, TC-A-01 |
| REQ-013 | Battery divider quiescent drain ≤ 5 µA | Performance | approved | TC-A-02 |
| REQ-014 | Battery divider software-disconnectable | Performance | approved | TC-A-02 |
| REQ-015 | MCU module ESP32-C6-MINI-1-N4 | Interface | approved | TC-D-00 |
| REQ-016 | MCU supply voltage 3.0–3.6V | Performance | approved | TC-D-00 |
| REQ-017 | Deep sleep total board current ≤ 20 µA | Performance | approved | TC-A-03, TC-P-06 |
| REQ-018 | WiFi 802.11ax (WiFi 6) at 2.4 GHz | Functional | approved | TC-S-00 |
| REQ-019 | BLE 5.0 support | Functional | approved | TC-S-01 |
| REQ-020 | I2C bus on external connector | Interface | approved | TC-D-01 |
| REQ-021 | UART on external connector | Interface | approved | TC-D-02, TC-D-03 |
| REQ-022 | SPI bus on external connector | Interface | approved | TC-D-03 |
| REQ-023 | Serial bus connector 3.3V and GND | Interface | approved | TC-C-02 |
| REQ-024 | USB-C connector for charging | Mechanical | approved | TC-C-00, TC-P-00 |
| REQ-025 | USB-C VBUS ESD protection | Safety | approved | TC-C-03, TC-P-00 |
| REQ-026 | ESP32 antenna keep-out zone observed | Mechanical | approved | TC-M-01 |
| REQ-027 | 100 nF decoupling caps near ESP32 VCC pads | Mechanical | approved | TC-M-02 |
| REQ-028 | Bulk 100 µF cap near ESP32 module | Mechanical | approved | TC-M-02 |
| REQ-029 | Battery monitor divider routed away from RF | Mechanical | approved | TC-M-00 |
| REQ-030 | Test points on 3.3V, GND, UART TX/RX, BOOT, RESET | Mechanical | approved | TC-M-03 |
| REQ-031 | WiFi MQTT communication with Raspberry Pi | Functional | approved | TC-S-02, TC-S-00 |
| REQ-032 | Configurable sleep interval persisted in NVS | Functional | approved | TC-S-02 |
| REQ-033 | Sleep OFF and Sleep ON operating modes | Functional | approved | TC-S-03, TC-S-02 |
| REQ-034 | Static IP, wake-to-TX ≤ 500 ms | Performance | approved | TC-S-04 |
| REQ-035 | ≥ 7 days runtime at 10 s wake interval | Performance | approved | TC-S-05 |
| REQ-036 | ≥ 45 days runtime at 30 s wake interval | Performance | approved | TC-A-03 |
| REQ-037 | PI4IOE5V6416 I2C GPIO expander | Interface | approved | TC-D-01 |
| REQ-038 | GPIO expander external module control signals | Functional | approved | TC-D-01 |
| REQ-039 | GPIO expander INT to IO22 for wake-from-sleep | Functional | approved | TC-D-01 |
| REQ-040 | GPIO expander 3.3V with 100 nF decoupling | Interface | approved | TC-D-01 |
| REQ-041 | ADS7828 12-bit 8-channel I2C ADC | Interface | approved | TC-D-01 |
| REQ-042 | ADC CH0 battery voltage monitoring | Functional | approved | TC-A-00, TC-A-01 |
| REQ-043 | Remaining ADC channels available | Functional | approved | TC-D-01 |
| REQ-045 | ADS7828 3.3V decoupling and VREF from REF3425 | Interface | approved | TC-A-04 |
| REQ-046 | Operate from USB alone | Functional | approved | TC-P-00, TC-D-00 |
| REQ-047 | Prioritise USB over battery when USB connected | Functional | approved | TC-P-01 |
| REQ-048 | Simultaneous charging and system operation | Functional | approved | TC-P-01, TC-P-05 |
| REQ-049 | BOOT pin USB bootloader access | Interface | approved | TC-M-03, TC-D-00 |
| REQ-050 | SX1276 LoRa 868 MHz transceiver | Functional | approved | TC-L-00 |
| REQ-051 | SX1276 on SPI2 with IO4 NSS | Interface | approved | TC-D-03, TC-L-00 |
| REQ-052 | SX1276 DIO0 interrupt on IO5 | Interface | approved | TC-L-01 |
| REQ-053 | SX1276 RESET via GPIO expander | Interface | approved | TC-D-01 |
| REQ-054 | SX1276 SMA connector 50 Ω matched trace | Interface | approved | TC-M-00 |
| REQ-055 | SX1276 RF positioned away from ESP32 antenna | Mechanical | approved | TC-M-01 |
| REQ-056 | SX1276 sleep mode during ESP32 deep sleep | Performance | approved | TC-A-03 |
| REQ-057 | LoRa and WiFi concurrent operation | Functional | approved | TC-L-02 |
| REQ-058 | REF3425 2.5V precision voltage reference | Interface | approved | TC-A-04 |
| REQ-059 | Bidirectional battery current measurement via INA333 | Functional | approved | TC-D-01 |
| REQ-060 | INA333 power-gated during deep sleep | Performance | approved | TC-A-03, TC-P-06 |
Trace Link Graph
■ Done ■ Partial ■ Not started ■ No test case
Verification Records
No verification records.
Decisions
E-001
Bus pin assignments for ESP32-C6
info
2026-05-26
GPIO assignments constrained by ESP32-C6-MINI-1-N4 fixed-function pins (UART0, USB) and available GPIO matrix pins. LP_I2C assigned to dedicated low-power capable pins (IO6/IO7). IO4 and IO5 originally reserved for JTAG (MTMS/MTDI) — reservation removed 2026-04-12; reassigned to SX1276 NSS and DIO0.
Trade-offs: IO9 (I2C0 SCL) is a boot strapping pin — I2C pull-up holds it high at boot (safe). IO15 (UART1 RX) is a strapping pin for JTAG source. All GPIOs fully allocated except IO23.
E-002
KiCad schematic sheet structure — 4 sheets
info
2026-05-26
Logical separation of subsystems improves readability and parallel review. Power sheet is self-contained for electrical safety review. MCU sheet isolates digital complexity.
Trade-offs: Cross-sheet signals require KiCad hierarchical labels. USB D-/D+ route from Power sheet to MCU sheet. LP_I2C routes from MCU sheet to On-board Peripherals sheet.
E-003
BQ24075T passive network configuration
info
2026-05-26
ISET and ILIM share 1.5kΩ value for BOM consolidation. TMR=56kΩ gives ~7h fast-charge timer adequate for LiPo cells. NTC thermistor function disabled — divider holds TS at valid level to prevent fault.
Trade-offs: ISET=1.5kΩ → ~593 mA charge current → ~0.77W dissipation on BQ24075; thermal pad copper pour required; BQ24075 TREG will throttle if die overheats. SYSOFF must not be pulled to VBUS. CE must not be pulled to VBUS.
E-004
PI4IOE5V6416ZDEX I2C address and port allocation
info
2026-05-26
Address 0x20 selected (no conflict with ADS7828 at 0x48). All 6 connector signals grouped on Port 0 for single-register read. LORA_RESETn on P10 (Port 1) is isolated from connector signals.
Trade-offs: RESET pin passively pulled to VCC via 10kΩ (no free MCU GPIO for soft-reset); I2C General Call Reset available as software alternative. INT pin is open-drain; 10kΩ pull-up to 3.3V; routed to IO22.
E-005
ADS7828 I2C address 0x48
info
2026-05-26
No conflict with PI4IOE5V6416 at 0x20. Simplest configuration — both address pins tied to GND.
Trade-offs: Address is fixed in hardware; cannot be changed without PCB rework.
E-006
J_EXT connector pinout (AXK5S60047) — deviations from reference
info
2026-05-26
Deviations required to expose REQ-038 module control signals (SHDNn, RESETn). No other adjacent NC pins available in that row. VREF exposed for potential mating board use.
Trade-offs: Mating cable/PCB MUST NOT connect pins 16 or 18 to GND — deviates from reference product. VREF (pin 7) limited drive; buffer required on mating board if load >5 mA.
E-007
UART0 TX/RX test access via 1×2 2.54 mm pin headers
info
2026-05-26
If USB-CDC proves unreliable on prototype, headers allow a standard USB-serial adapter for UART0 access. Headers serve as test points when unpopulated.
Trade-offs: Prototype decision — revisit after board verification. If USB-CDC reliable: leave DNP in R1. If unreliable: populate and consider dedicated UART connector in R1. Partially satisfies REQ-030.
E-008
Battery current sense — INA333 + 100 mΩ shunt + AO3407 PMOS power-gate
info
2026-05-26
Bidirectional measurement needed to validate REQ-035/036 battery life estimates. ADS7828 CH1 was spare — no extra I2C device needed. PMOS power-gate preserves REQ-017 deep sleep budget (INA333 Iq=50µA otherwise exceeds 20µA limit). PI4IOE P06 was NC — zero cost.
Trade-offs: Adds R_SHUNT in battery series path (minor voltage drop at 600mA). Firmware must manage SHUNTn enable/disable around deep sleep entry/exit.
E-009
SX1276 32 MHz crystal — ECS-320-10-37B-CKY-TR3 for R0 prototype
info
2026-05-26
NDK NX2016SA unavailable at DigiKey/Mouser at time of BOM build. ECS ECX-1637B series is direct drop-in: 2016 4-pad footprint, CL=10pF, ESR≤50Ω, ±10ppm — all within SX1276 crystal requirements.
Trade-offs: ECS part used for prototype only. NX2016SA should be evaluated at production BOM review (REQ-061). No functional difference expected.
Design Rule Status
■ No violations ■ Warning ■ Error ■ Waived
Bill of Materials
| Ref | Part # | Part Name | Category | Qty | Description |
|---|---|---|---|---|---|
| C1 | EGP10000653 | Capacitor 10u | Capacitor | 1 | — |
| C10 | EGP10000651 | CAP0402 2u2F | Capacitor | 1 | — |
| C11 | EGP10000653 | Capacitor 10u | Capacitor | 1 | — |
| C12 | EGP10000653 | Capacitor 10u | Capacitor | 1 | — |
| C13 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C14 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C15 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C16 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C17 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C18 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C19 | EGP10000652 | Capacitor 4u7 | Capacitor | 1 | — |
| C2 | EGP10000653 | Capacitor 10u | Capacitor | 1 | — |
| C20 | EGP10000593 | Capacitor 10p | Capacitor | 1 | — |
| C21 | EGP10000593 | Capacitor 10p | Capacitor | 1 | — |
| C22 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C23 | EGP10000595 | Capacitor 15p | Capacitor | 1 | — |
| C24 | EGP10000595 | Capacitor 15p | Capacitor | 1 | — |
| C25 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C26 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C27 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C28 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C29 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C3 | EGP10000653 | Capacitor 10u | Capacitor | 1 | — |
| C30 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C4 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C5 | EGP10000650 | CAP0402 1uF | Capacitor | 1 | — |
| C6 | EGP10001791 | A782MS227M1VLAS020 | Capacitor | 1 | — |
| C7 | EGP10001454 | CAP0805 10uF 50V | Capacitor | 1 | — |
| C8 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| C9 | EGP10000641 | CAP0402 100nF | Capacitor | 1 | — |
| D1 | EGP10001684 | APT2012G | Diode | 1 | — |
| D2 | EGP10001684 | APT2012G | Diode | 1 | — |
| FB1 | EGP10001889 | MPZ2012S102 | Inductor | 1 | — |
| J1 | EGP10001935 | S2B-PH-K-S | Connector | 1 | — |
| J2 | EGP10001938 | 632723100011 | Connector | 1 | — |
| J3 | EGP10001412 | Q2 B2B conn receptacle | Connector | 1 | — |
| J4 | EGP10001928 | Conn SMA Surface Mount | Connector | 1 | — |
| L1 | EGP10001937 | LQW15AN15NG80D | Inductor | 1 | — |
| PCB1 | EGP10001925 | PCB Accordion Beacon Module R0 | PCB | 1 | — |
| Q1 | EGP10001761 | AO3407 | Transistor | 1 | — |
| R1 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R10 | EGP10000077 | Resistor 1k5 | Resistor | 1 | — |
| R11 | EGP10000077 | Resistor 1k5 | Resistor | 1 | — |
| R12 | EGP10000077 | Resistor 1k5 | Resistor | 1 | — |
| R13 | EGP10000077 | Resistor 1k5 | Resistor | 1 | — |
| R14 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R15 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R16 | EGP10000145 | Resistor 1M | Resistor | 1 | — |
| R17 | EGP10000145 | Resistor 1M | Resistor | 1 | — |
| R18 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R19 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R2 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R20 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R21 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R22 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R23 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R24 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R25 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R26 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R27 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R28 | EGP10001011 | Resistor 0805 100m | Resistor | 1 | — |
| R29 | EGP10000121 | Resistor 100k | Resistor | 1 | — |
| R3 | EGP10000128 | Resistor 200k | Resistor | 1 | — |
| R30 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R31 | EGP10000001 | Resistor 0 | Resistor | 1 | — |
| R32 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R33 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R34 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R35 | EGP10000001 | Resistor 0 | Resistor | 1 | — |
| R36 | EGP10000001 | Resistor 0 | Resistor | 1 | — |
| R37 | EGP10000121 | Resistor 100k | Resistor | 1 | — |
| R38 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R39 | EGP10000097 | Resistor 10k | Resistor | 1 | — |
| R4 | EGP10000121 | Resistor 100k | Resistor | 1 | — |
| R5 | EGP10000121 | Resistor 100k | Resistor | 1 | — |
| R6 | EGP10001147 | Resistor 49k9 | Resistor | 1 | — |
| R7 | EGP10000121 | Resistor 100k | Resistor | 1 | — |
| R8 | EGP10000121 | Resistor 100k | Resistor | 1 | — |
| R9 | EGP10000115 | Resistor 56k | Resistor | 1 | — |
| U1 | EGP10001929 | BQ24075TRGTR | IC | 1 | — |
| U10 | EGP10001934 | INA333AIDGKT | IC | 1 | — |
| U2 | EGP10001930 | MCP1700T-3302E/MB | IC | 1 | — |
| U3 | EGP10001931 | ESP32-C6-MINI-1-N4 | IC | 1 | — |
| U4 | EGP10001794 | SRV05-4LA 4A | Diode | 1 | — |
| U5 | EGP10001021 | PI4IOE5V6416ZDEX | IC | 1 | — |
| U6 | EGP10000946 | ADS7828EB/2K5 | IC | 1 | — |
| U7 | EGP10001154 | REF3425TIDBVR | IC | 1 | — |
| U8 | EGP10001932 | SX1276IMLTRT | IC | 1 | — |
| U9 | EGP10001933 | 4259-63 | IC | 1 | — |
| X1 | EGP10001939 | ECS-320-10-37B-CKY-TR3 | Crystal | 1 | — |