Project Details

  Three Pico W boards act as BLE temperature sensors. Each runs a short BASIC program that wakes up  once a minute, formats a reading as `lanai_f=82\r\n`, and transmits it over BLE NUS Nordic UART  Service) — essentially a serial port over Bluetooth. A Raspberry Pi 3B runs a Python gateway that   bridges those BLE packets to a local Mosquitto MQTT broker and simultaneously POSTs the values to  the Pico 2 W via a simple HTTP GET: `/?lanai_f=82`. The Pico 2 W serves the dashboard page, and a  `<?web lanai_f ?>` tag in the HTML substitutes the live value when any browser loads it. Two Shelly  smart plugs on the same broker handle the lights — a button on the page calls a BASIC subroutine  that publishes `on` or `off` to the Shelly's MQTT topic.

  The whole thing runs on your LAN. No AWS, no Google, no subscription. It's also accessible  remotely via a Cloudflare tunnel — no port forwarding, no static IP required.

   Getting the radio up

  None of that works until the CYW43 WiFi/BT co-processor on the Pico 2 W is talking. That chip expects the Pico SDK runtime — clocks, DMA, PIO, an async context, a ~225 KB firmware blob streamed over SPI at startup. ARMbasic has its own hand-rolled startup and none of that. Getting the chip to cooperate meant reverse-engineering exactly which pieces of the SDK the radio actually needs and replaying them by hand.

  It did not go quietly. Three genuinely nasty bugs: a linker change that shoved the vector table off `0x10000000` and silently killed USB enumeration; the WiFi PIO state machine landing on PIO2,  which the custom startup left in reset, so every register write evaporated and the first SPI transfer hung forever; and — the sneakiest — the chip joining the network fine while the driver sat stuck at "JOINING," because the host-wake interrupt was stubbed out and the join-complete event was never delivered.

  BLE on the sensor nodes had its own moment. The `TXD(ch) = value` statement in BASIC is supposed  to send a byte to a specific serial channel — channel 3 is BLE NUS. The hardware worked, the  connection was up, bytes were arriving from the phone. But nothing ever came back. After adding  debug prints up the call chain, it turned out `TXD(ch) = value` had been silently calling `WAIT(value)` instead. The compiler's code-generation table had `OP_SET_TXD` falling through to  `CMD_WAIT` — three opcodes sharing one handler, all routing to the wrong function. Nobody noticed  because multi-channel serial was rarely exercised on targets where the channels did anything  interesting. Sending `TXD(3) = 0xE8` was pausing the program for 15 seconds. One line fix, one  recompile, it worked.

  Drag-and-drop authoring

  Pages are flash files authored by drag-and-drop. Plug the board in, a USB drive named *ARMbasic  Pages* appears, drop your `.html` on it, eject — and it's live over WiFi a second later. The  eject *is* the save gesture; it commits the RAM write-back buffer to flash. No FTP, no toolchain,  no reflash just to change the page layout.  Dynamic content uses a PHP-style template tag, `<?web … ?>`, embedded directly in the HTML. Tags can substitute a variable, call a BASIC function and inline its return value, evaluate a small expression, or branch with `if/else`. The dashboard uses them to show the four temperatures,  render the light state badges, and conditionally color the on/off buttons.  There's no on-chip  compiler — the PC compiles the BASIC program; the chip keeps the symbol table (names and  addresses) and a small template evaluator. Scripting in the page costs a few KB, not a language runtime.

  The bigger picture

  You can't win the board business anymore, so don't play it. The Pico ships by the million at a  price no small shop can match. The value is the software that makes it do something specific and  delightful. ARMbasic is a 25-year-old compiler that started on NXP LPC parts, has since been ported to a dozen Cortex-M chips, and just learned to serve the web and bridge BLE. It boots to a  `>`prompt, compiles to native ARM Thumb-2, and the entire user interaction model — write BASIC on  the PC, drag HTML to the board, browser hits the page — fits in an afternoon.

  The full source is in the [ARMbasic repository](https://coridium.us) under `bin/Examples/`.

This project is nearly complete, just waiting for some PCBs from OSHpark for the temperature sensors.