Sparrow is the concentrator and gateway board for the BEEFASYER apiary-monitoring hardware platform. It collects data from Bluebird, Crane, and other compatible sensor boards, then forwards that data to the Beeforesight software platform over Wi-Fi or LTE-M using MQTT and ChirpStack.
Each BEEFASYER monitoring network is centered on exactly one Sparrow.
Important
This project includes power electronics, battery charging, USB Power Delivery, and solar input circuitry. Observe the electrical and thermal limits described in this document before connecting batteries, power supplies, or external modules. Project is in alpha public testing.
The BEEFASYER hardware family consists of three main boards:
| Board | Role | Primary connectivity |
|---|---|---|
| Sparrow | Apiary concentrator and gateway | Wi-Fi, BLE, LoRaWAN, optional LTE-M |
| Bluebird | In-hive environmental sensor | BLE |
| Crane | External environmental and hive-weight sensor | LoRa and BLE |
Together, these boards form one monitoring network per apiary and feed the Beeforesight software platform.
flowchart LR
B[Bluebird<br>In-hive sensor] -->|BLE| S[Sparrow<br>Gateway]
C[Crane<br>External sensor] -->|LoRa / BLE| S
X[Additional boards] --> S
S -->|Wi-Fi or LTE-M<br>MQTT / ChirpStack| F[Beeforesight]
F --> I[(InfluxDB)]
F --> P[(PostgreSQL)]
- ESP32-C6 with 4 MB flash
- Wi-Fi 6 at 2.4 GHz
- Bluetooth 5 Low Energy
- IEEE 802.15.4 radio for Zigbee and Thread
- External Wi-Fi/BLE antenna connection through IPEX/U.FL
- Ultra-low-power RISC-V core for scheduled monitoring
- MCP23017 16-bit I²C GPIO expansion
- USB and solar power inputs
- USB Power Delivery negotiation up to 20 V / 4 A
- BQ25798 buck-boost battery charger with MPPT
- Battery support for Li-ion, Li-Po, and LiFePO₄
- Always-on, firmware-configurable auxiliary output
- Optional LoRaWAN concentrator and LTE-M/GNSS modules
- External OLED, rotary encoder, and button interface
- Up to 32 BLE connections
- Internal USB JTAG programming
Sparrow is built around the ESP32-C6, a RISC-V system-on-chip with Wi-Fi, BLE, and IEEE 802.15.4 connectivity.
The ESP32-C6 contains:
- A high-performance application core
- A separate low-power RISC-V core
- Wi-Fi 6 support on the 2.4 GHz band
- Bluetooth 5 LE
- Zigbee and Thread-capable IEEE 802.15.4 radio
The low-power core can wake every 30 seconds to listen for interrupts and monitor power-related conditions. Sleep and wake schedules are configurable in firmware.
An MCP23017 I²C GPIO expander provides 16 additional GPIO lines for functions such as status LEDs and external controls.
Sparrow can communicate directly with Bluebird and Crane boards and can maintain up to 32 BLE connections. With the optional WM1302 module installed, it also operates as a multi-channel LoRaWAN concentrator.
Collected data is published to the server through MQTT, using ChirpStack where applicable.
Sparrow's power system is based on the following devices:
| Component | Purpose |
|---|---|
| BQ25798 | I²C-controlled 1–4-cell buck-boost battery charger, MPPT controller, and power-path manager |
| TPS25730D | USB Type-C and USB Power Delivery controller |
| TPS62903 | Wide-input synchronous step-down converter for the system logic rail |
Sparrow supports two main power sources:
- USB-C
- Solar or external DC input
The USB input can negotiate a contract of up to 20 V / 4 A through the TPS25730D.
The solar input supports a nominal 24 V panel and uses the BQ25798's MPPT functionality. It can also be used with another external device that provides a stable supply.
The BQ25798 input charging current is currently limited to 2 A.
Although the limit can be increased in firmware, it must not be raised until the battery connector has been redesigned. The existing connector is the primary 2 A bottleneck.
Warning
At a 2 A charging current, the charger can exceed 70 °C and may thermally throttle unless an appropriate metal heat spreader is installed.
The BQ25798 drives the main VSYS rail at approximately battery voltage. VSYS is software-adjustable, but settings below 3.5 V may cause system problems.
The TPS62903 converts the battery voltage to the logic rail used by the rest of the board.
One firmware-configurable output remains powered even when the main system is off. It can be used to supply another board or an external low-power device.
Supported battery chemistries include:
- Li-ion
- Li-Po
- LiFePO₄
The BQ25798 PROG pin is configured for a 1S battery by default. Higher-voltage battery packs require the charge voltage to be changed through the appropriate PROG resistor or charger register configuration.
| Pack | Status | Notes |
|---|---|---|
| 1S | Default | Matches the default PROG configuration |
| 2S | Supported with configuration | Charge-voltage settings must be updated |
| 3S | Supported in principle | Within the TPS62903 input range |
| 4S | Marginal / not recommended | A fully charged pack reaches 16.8 V, close to the converter's approximate 17 V input limit |
Caution
Treat 4S operation as conditional and electrically marginal. Component tolerances, transients, and supply conditions may exceed the converter's safe input range.
Sparrow provides two mPCIe-format expansion slots.
The inward-facing slot is intended for the Seeed WM1302 LoRaWAN concentrator.
The WM1302 is based on the Semtech SX1302 and provides multi-channel reception, allowing Sparrow to operate as a true LoRaWAN gateway. It can communicate with LoRa nodes such as RAK4631-based devices.
The outward-facing slot is intended for the Quectel BG95-M3.
The BG95-M3 supports:
- LTE Cat M1 / LTE-M
- LTE Cat NB2 / NB-IoT
- EGPRS
- GNSS
Its primary purpose on Sparrow is LTE-M backhaul when Wi-Fi is unavailable.
An external control surface connects through a 9-pin JST-SH connector and may include:
- SH1106 128 × 64 monochrome OLED
- EC11 rotary encoder
- Four additional buttons
These parts may be sourced as standard off-the-shelf modules.
Note
The SH1106 is similar to the SSD1306, but it uses a different display-memory column offset. SSD1306 drivers may require adjustment.
- Every BEEFASYER network requires exactly one Sparrow.
- Sparrow pairs directly with Bluebird and Crane sensor boards.
- Up to 32 BLE connections are supported.
- LoRaWAN operation requires the WM1302 concentrator module.
- LTE-M operation requires the BG95-M3 cellular module and network provisioning.
A typical deployment uses Bluebird boards inside hives, Crane boards outside hives, and one Sparrow as the apiary gateway.
Sparrow is programmed through its internal USB JTAG interface.
- ESP-IDF — preferred
- Arduino IDE — supported
- MicroPython and other environments — currently untested
Repository-specific build, flash, configuration, and provisioning instructions should be documented alongside the firmware source as the software layout stabilizes.
| Component | Function |
|---|---|
| ESP32-C6 | Main RISC-V MCU with Wi-Fi 6, BLE, and IEEE 802.15.4 |
| MCP23017 | 16-bit I²C GPIO expander |
| BQ25798 | Buck-boost battery charger, power-path manager, and MPPT controller |
| TPS25730D | USB Type-C / USB Power Delivery controller |
| TPS62903 | Wide-input synchronous buck converter |
| WM1302 | SX1302-based multi-channel LoRaWAN concentrator |
| BG95-M3 | LTE-M, NB-IoT, EGPRS, and GNSS module |
| SH1106 | 128 × 64 monochrome OLED controller |
| EC11 | Rotary encoder with push-button function |
- Charging current must remain limited to 2 A with the current battery connector.
- Charger thermal performance requires careful validation and may require a metal heat spreader.
- VSYS values below 3.5 V may cause unreliable operation.
- The default charger configuration is for a 1S battery.
- 4S battery operation is marginal because of the TPS62903 input-voltage limit.
- MicroPython and toolchains other than ESP-IDF or Arduino are untested.
- LTE-M and LoRaWAN features require their respective expansion modules.
Before powering the board:
- Confirm the battery chemistry, cell count, and charger configuration.
- Verify input polarity and voltage.
- Keep the charging-current limit at or below 2 A with the current connector.
- Provide suitable thermal management around the charger.
- Do not assume that 4S battery operation is safe without additional validation.
- Disconnect power before installing or removing expansion modules.
BEEFASYER Sparrow is an actively developed hardware platform. Electrical limits, firmware behavior, interfaces, and supported configurations may change as the design is validated and revised.