// 03 HARDWARE

HaLow Ink

KICAD ESP-IDF BLENDER WALKTHROUGH

A pocket Wi-Fi HaLow node built around Heltec's HT-HC01 module: an ESP32-S3 drives the 902–928 MHz radio and a 2.9-inch e-paper screen, and a LiPo charged over USB-C should run it for months between reports. The 85 × 40 mm four-layer board was generated from one Python design file, autorouted, and passes KiCad's electrical and design rule checks; the case is three prints. Designed and rendered, not yet built.

> Wi-Fi below 1 GHz, and the board I designed for iton YouTube1:30

HaLow Ink standing on its USB edge: a graphite 3D-printed case with an e-paper screen reading HaLow Ink, SSID HT-H7608-halow, IP 192.168.100.123, RSSI −67 dBm, MQTT sent, and a black 915 MHz antenna leaning back from the top edge beside two orange buttons

01 Assembled, display side

HaLow Ink taken apart along its thickness: four screws, the back shell with the name debossed, a LiPo cell, the HT-HC01 module lifted off the black four-layer board, the e-paper panel with its orange flex, the front bezel and two orange button caps, with the antenna above

02 Exploded, component side

A line drawing of the exploded assembly with numbered balloons 1 to 12 on leader lines, dashed assembly lines from each screw to its boss, and a parts list in a title block

03 Exploded drawing, parts 1 to 12

Close-up of the black PCB: the HT-HC01's silver shield can labelled HT-HC01 Wi-Fi HaLow on a blue module board with gold castellations, the ESP32-S3 module beside it, a tantalum capacitor and the e-paper flex connector

04 The board, HT-HC01 in focus

The back of the case with HaLow Ink and 802.11ah 915 MHz rev A debossed, four screw heads in the corners, a vent grille and a reset pinhole, the antenna leaning back from the top

05 Assembled, back

What is on the board

Radio: Heltec HT-HC01 (Morse Micro MM6108, 21 dBm), on SPI at up to 40 MHz, wired the way Heltec's own HT-HC32 is, with a U.FL to an SMA bulkhead.
Host: ESP32-S3-WROOM-1 with 16 MB flash and 8 MB PSRAM, flashed over its own USB.
Display: a 2.9-inch 296 × 128 SSD1680 e-paper panel on the back of the board, its flex folded round the end.
Power: USB-C, an MCP73831 charger, a power path that lets USB run the board while it charges, and a 1 A regulator that idles at 8 µA.
Extras: two buttons, a Qwiic connector, pads for a DHT11 and four spare GPIO, on a rail the firmware can switch off.

Power

The radio draws about 220 mA transmitting and 30 to 40 mA listening, but under half a milliamp while associated in power save and about 1 µA asleep. Reporting every ten minutes, the whole board should average around 12 mAh a day: about five months on a 2000 mAh cell. Those are estimates from the module's datasheet, not measurements.

Status

The schematic passes KiCad's ERC; its netlist matches the design file pin for pin; the board passes DRC with nothing unrouted.
JLCPCB stocks 36 of the parts, about $10 a board; the HT-HC01 is soldered by hand.
The ESP-IDF firmware builds: it joins a HaLow access point, reports over MQTT, redraws the screen and sleeps. It has never run on hardware.
The antenna match is untuned, the routing is unreviewed and the case is unprinted.

Made with

KiCad 10 from a Python generator with its own maze router, Blender 5.1 Cycles for the renders, OpenSCAD for the case, and three.js for the walkthrough's model you can take apart.