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Atlas — Requirements & Task Backlog

Project: Atlas Author: Anton Chernov Date: 06/29/2026 Version: 0.1.0

1. Requirements

REQ-001 — Star Hub Receiver

Atlas shall receive periodic readings from up to 20 Psychrometer nodes over an nRF24L01+ star network.

Acceptance criteria:

  • Hub MCU STM32F103C8T6 + nRF24L01+ in PRX role.
  • 6 hardware pipes; node id field in payload identifies up to 20 nodes.
  • Auto-ACK with retransmit; each node keeps a unique pipe address.

REQ-002 — Packet Format

A compact fixed payload (<= 32 bytes) shall carry node id, sensor data and a status/battery field, identical to the Psychrometer node struct.

Acceptance criteria:

  • Fields: node id, T, H, P, battery/status; documented byte layout.
  • Endianness defined; same struct on node and hub.

REQ-003 — Display: BC2004BGPLCH6

Atlas shall show per-node temperature, humidity, pressure and last-seen state on a 20x4 HD44780 LCD.

Acceptance criteria:

  • 4-bit interface, R/W tied low (write only).
  • Carousel/scroll across nodes (3-4 per screen).
  • Stale flag when a node misses N transmit periods.

REQ-004 — Auto Brightness and Contrast

A BH1750 ambient light sensor shall drive backlight and contrast automatically.

Acceptance criteria:

  • BH1750 read over I2C; lux mapped to PWM duty.
  • Backlight via switched PWM; contrast via PWM + RC on V0.
  • Hysteresis to avoid flicker.

REQ-005 — Optional Server Uplink

Atlas may concentrate readings toward a local server.

Acceptance criteria:

  • Uplink isolated behind an interface; absence does not block core function.
  • Transport: ENC28J60 (SPI dev board) toward a local server.
  • Defined message format for forwarded readings.

REQ-006 — Scheduler: AcroSched 1.7

Task flow shall run on AcroSched, shipped as a prebuilt library plus headers (sources private). Parameters are compile-time and frozen at build:

Acceptance criteria:

  • ACROSCHED_MAX_TASKS = 12; watchdog, timers (MAX_TIMERS = 4), IPC and idle hook enabled; introspection/stats/hooks disabled.
  • Cortex-M3 lib for AC6 and GCC; app provides SysTick tick and config defines.
  • IPC mailbox carries nRF packets from ISR to task; idle hook calls __WFI().

REQ-007 — Bare-register Implementation

The hub shall be implemented with CMSIS-Toolbox using direct register access; no HAL, no CubeMX.

Acceptance criteria:

  • Clock, GPIO, SPI1, I2C1, timers/PWM configured via registers.
  • Only CMSIS device headers used.

REQ-008 — Multi-platform Structure

Common code shall be MCU-independent; STM32F103 specifics live in the port layer.

Acceptance criteria:

  • inc/ and src/ contain no MCU-specific registers.
  • Port directory selects platform code only.

REQ-009 — No Dynamic Memory

Static allocation only; no malloc/free.

REQ-010 — Doxygen Documentation

All public headers, types and functions documented with Doxygen tags; docs/ holds the Doxyfile and diagrams.

2. Task Backlog

Phase 0 — Foundation

  • T001 — Repository structure (inc/ src/ port/ docs/)
  • T002 — Requirements, HISTORY, CHANGELOG
  • T003 — CMSIS-Toolbox project skeleton (STM32F103C8T6)

Phase 1 — Hub bring-up

  • T010 — Clock + GPIO + SysTick (bare registers)
  • T011 — AcroSched lib (.a + headers), SysTick + acroInit
  • T012 — SPI1 + nRF24L01+ PRX, multi-pipe, packet struct
  • T013 — I2C1 + BH1750 driver

Phase 2 — Display

  • T020 — LCD 4-bit driver, per-node table + stale flag
  • T021 — Carousel/scroll across nodes

Phase 3 — Auto bright/contrast

  • T030 — Backlight + contrast PWM
  • T031 — BH1750 mapping with hysteresis

Phase 4 — Server uplink

  • T040 — ENC28J60 driver + uplink task to local server

Phase 5 — Documentation

  • T050 — Doxygen, schematics, pin map