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+---
+slug: pico-ws
+title: "Pico Ws"
+date: "2022-11-11T05:30:53-04:00"
+
+pics:
+  reel:
+    css: "image"
+    tip: "Reel of Raspberry Pi Pico Ws."
+    sources:
+      - src: "/files/posts/pico-ws/pico-w-reel.jpg"
+        width: 1024
+        height: 768
+  single:
+    css: "image"
+    tip: "Individual Pico W."
+    sources:
+      - src: "/files/posts/pico-ws/pico-w-single.jpg"
+        width: 1024
+        height: 768
+  testing:
+    css: "image"
+    tip: "Advanced Pico W testing facility."
+    sources:
+      - src: "/files/posts/pico-ws/pico-w-testing.jpg"
+        width: 1024
+        height: 768
+---
+Last month I got a reel of [Raspberry Pi Pico Ws][pico-w].  Several
+will eventually be paired with [BME280s][bme280] and used to measure
+temperature, humidity, and barometric pressure throughout the house.
+
+That project will have to wait a few weeks until I can unpack my
+soldering iron.
+
+In the mean time I've been fiddling [MicroPython][].  My thoughts so far
+are below...
+
+### Ordering and Delivery
+
+Ordering was a bit of a headache.  The sites that I normally buy
+from all had one or more of the following annoyances:
+
+* Ridiculous markup
+* Outrageous shipping fees
+* Comically low quantity limit
+
+The [Pico][] and [Pico W][pico-w] are not supply chain constrained like
+the [Raspberry Pi 4B][pi-4b] and [Raspberry Pi Zero 2 W][pi-zero-2-w],
+so I'm not sure why retailers are doing this.
+
+I finally checked [DigiKey][], and they had plenty of [Pico Ws][pico-w]
+in stock and none of the aforementioned shenanigans.  I ordered a reel
+of 20 [Pico Ws][pico-w] for $6.00 apiece on October 3rd.  The package
+arrived on October 5th.
+
+As of this writing, [DigiKey][] still has [over 15,000 Pico Ws in
+stock][stock].
+
+### Hardware
+
+Thoughts:
+
+* 264 kB of RAM feels quite roomy on a microcontroller.
+* Built-in [wifi][] is incredibly useful because you don't have to
+  sacrifice a bunch of pins for external communication.
+* PIO looks promising, although I haven't really used it yet.
+* The onboard temperature sensor is not very accurate.
+
+### Flashing [MicroPython][]
+
+Flashing via [USB mass storage][] is great.  I didn't have to install an
+[SDK][], fight with finicky wiring, or use an obscure microcontroller
+flashing tool.
+
+To get up and running with [MicroPython][], you can follow [these
+instructions][flash-instructions].  The basic steps in [Linux][] are as
+follows:
+
+1. Press the BOOTSEL button on the [Pico W][pico-w].
+2. Connect the [Pico W][pico-w] to your computer via [USB][].  It
+appears as [USB mass storage][] device.
+3. Mount the mass storage device.  Many distributions will automatically
+mount the device for you as `/media/RPI-RP2`.
+4. Copy a [UF2][] image to the mounted disk.
+5. The [Pico W][pico-w] will flash itself and reboot.
+
+If you've flashed [MicroPython][], then at this point you can connect to
+a [REPL][] via [USB][] serial (e.g. `screen /dev/ttyACM0`).
+
+The [Pico][] and [Pico W][pico-w] have [SWD][] pins, so you can still
+flash via [SWD][] if you want to; instructions are available in the
+[documentation][].
+
+### MicroPython
+
+[MicroPython][] is fantastic.  I was able to blink the onboard [LED][],
+read the onboard temperature sensor, connect to [wifi][], and make web
+requests less than an hour after unpacking the [Pico W][pico-w].
+
+#### Example: Blink [LED][]
+
+```python
+MicroPython v1.19.1 on 2022-10-06; Raspberry Pi Pico W with RP2040
+Type "help()" for more information.
+>>> led = machine.Pin('LED', machine.Pin.OUT) # get LED
+>>> led.toggle() # enable LED
+>>> led.value() # check status
+1
+>>> led.toggle() # disable LED
+>>> led.value() # check status
+0
+>>>
+```
+ 
+
+#### Example: Connect to [Wifi][] and send an [HTTP][] request
+
+```python
+MicroPython v1.19.1 on 2022-10-06; Raspberry Pi Pico W with RP2040
+Type "help()" for more information.
+>>> import network
+>>> wifi = network.WLAN()
+>>> wifi.active(True) # enable wifi
+>>> wifi.connect('ssid', 'password') # replace 'ssid' and 'password' with your SSID and password
+>>> wifi.status() # wait until wifi is connected (e.g., status = 3)
+3
+>>> import urequests
+>>> data = urequests.get('https://pablotron.org/').content # send http request, get response body
+>>> len(data) # print number of bytes received
+48693
+```
+ 
+
+One useful tip: `machine.unique_id()` returns a unique ID for the
+device.  This is useful because it allows you to flash the same image to
+several [Pico Ws][pico-w] and then use `machine.unique_id()` to uniquely
+identify them.  Example:
+
+```python
+>>> import binascii
+>>> binascii.hexlify(machine.unique_id())
+b'e6614c311b867937'
+```
+ 
+
+Miscellaneous [MicroPython][] notes:
+
+* Many of the libraries in the [MicroPython standard library][] are
+  reasonable subsets of their counterparts from the
+  [Python standard library][].
+* [MicroPython][] does not have [Pip][] or [PyPI][].  Instead you
+  install packages via [mip][].  I used it [mip][] install and use the
+  [MQTT][] library.
+* You can build a Unix version of [MicroPython][] by following the
+  [instructions in the `ports/unix` directory][build-unix] of the
+  [MicroPython Git repository][].
+* You can exhaust the RAM fairly easily by trying to fetch web content
+  which is larger than the available RAM.  Not that I would make such a
+  silly mistake...
+
+### Pictures
+
+{{< pe-figure "reel" >}}
+{{< pe-figure "single" >}}
+{{< pe-figure "testing" >}}
+
+Description of the last picture:
+
+* Foreground: [Pico W][pico-w] connected via [USB][] to a
+  [Raspberry Pi 4B (4GB)][pi-4b], sitting in a delivery container.  The
+  [Pi 4B][pi-4b] is used for miscellaneous `aarch64` testing like the
+  [hash benchmarks from June][hash].
+* Background: [Raspberry Pi 3B][pi-3b] in a proper case with a
+  [BME280][] soldered to it to the [I²C][i2c] pins.  The [Pi 3B][pi-3b]
+  is the bedroom [HTPC][] (running [Kodi][]) and temperature monitor.
+
+[pico]: https://www.raspberrypi.com/documentation/microcontrollers/raspberry-pi-pico.html
+  "Raspberry Pi Pico"
+[pico-w]: https://www.raspberrypi.com/documentation/microcontrollers/raspberry-pi-pico.html
+  "Raspberry Pi Pico W"
+[bme280]: https://www.bosch-sensortec.com/products/environmental-sensors/humidity-sensors-bme280/
+  "BME280 temperature, pressure, and humidity sensor."
+[i2c]: https://en.wikipedia.org/wiki/I%C2%B2C
+  "I²C microcontroller serial communication bus"
+[micropython]: https://micropython.org/
+  "Efficient Python 3 implementation for microcontrollers."
+[led]: https://en.wikipedia.org/wiki/Light-emitting_diode
+  "Light-emitting diode."
+[usb]: https://en.wikipedia.org/wiki/USB
+  "Universal Serial Bus"
+[usb mass storage]: https://en.wikipedia.org/wiki/USB_mass_storage_device_class
+  "USB mass storage device."
+[uf2]: https://github.com/microsoft/uf2
+  "UF2 flash file format"
+[sdk]: https://en.wikipedia.org/wiki/Software_development_kit
+  "Software Development Kit"
+[pico-sdk]: https://www.raspberrypi.com/documentation/microcontrollers/raspberry-pi-pico.html#software-development
+  "Raspberry Pi Pico and Pico W SDK."
+[flash-instructions]: https://www.raspberrypi.com/documentation/microcontrollers/micropython.html
+  "Instructions to flash MicroPython to a Pico W"
+[linux]: https://en.wikipedia.org/wiki/Linux
+  "Linux operating system"
+[repl]: https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop
+  "Read Evaluate Print Loop"
+[http]: https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol
+  "HyperText Transfer Protocol"
+[digikey]: https://digikey.com/
+  "DigiKey"
+[stock]: https://www.digikey.com/en/products/detail/raspberry-pi/SC0918/16608263
+  "Raspberry Pi Pico W at DigiKey"
+[pi-4b]: https://www.raspberrypi.com/products/raspberry-pi-4-model-b/
+  "Raspberry Pi 4B"
+[pi-3b]: https://www.raspberrypi.com/products/raspberry-pi-3-model-b/
+  "Raspberry Pi 3B"
+[pi-zero-2-w]: https://www.raspberrypi.com/products/raspberry-pi-zero-2-w/
+  "Raspberry Pi Zero 2 W"
+[swd]: https://en.wikipedia.org/wiki/JTAG#Similar_interface_standards
+  "Serial Wire Debug"
+[documentation]: https://www.raspberrypi.com/documentation/microcontrollers/raspberry-pi-pico.html#documentation
+  "Raspberry Pi Pico and Pico W Documentation"
+[build-unix]: https://github.com/micropython/micropython/tree/master/ports/unix
+  "ports/unix directory of MicroPython Git repository"
+[micropython git repository]: https://github.com/micropython/micropython
+  "MicroPython Git repository"
+[wifi]: https://en.wikipedia.org/wiki/Wi-Fi
+  "Wireless networking standard"
+[micropython standard library]: https://docs.micropython.org/en/latest/library/index.html#python-standard-libraries-and-micro-libraries
+  "MicroPython standard library"
+[python]: https://python.org/
+  "Python programming language"
+[python standard library]: https://docs.python.org/3/
+  "Python standard library"
+[micropython-lib]: https://github.com/micropython/micropython-lib/
+  "micropython-lib Git repository"
+[mqtt]: https://en.wikipedia.org/wiki/MQTT
+  "MQ Telemetry Transport"
+[pip]: https://pypi.org/project/pip/
+  "Python package installer"
+[pypi]: https://pypi.org/
+  "Python package index"
+[mip]: https://docs.micropython.org/en/latest/reference/packages.html#package-management
+  "micropython package management library"
+[htpc]: https://en.wikipedia.org/wiki/Home_theater_PC
+  "Home theater PC"
+[kodi]: https://kodi.tv/
+  "Kodi entertainment center"
+[hash]: {{< relref "posts/2022-06-10-hash-speeds.md" >}}
+  "OpenSSL Hash Benchmarks"