stonehippo

RP2040 Serial Tap

I wanted a very basic serial tap, a device I can insert between two other devices that are communicating via UART serial, so that I can inspect the messages going over the wire in real time.

The following are two implementations of this basic tap using an RP2040-based board, like a Raspberry Pi Pico. It takes advantage of the fact that the RP2040 has two UARTs, in addition to the USB serial used for programming and the REPL. There is one implementation in CircuitPython and another in MicroPython.

stonehippo

Setting up an Adafruit hardware realtime clock module and rtc in Circuitpython

The rtc module in CircuitPython is a standardized interface for realtime clock (RTC) devices. While it is possible to use an RTC directly from the instance of an RTC hardware driver, wrapping it with rtc has a couple of advantages:

• time.time() and time.localtime() are backed by rtc, all clock source will be synchronized
• rtc correctly handled the tm_yday (yearday) parameter, which may not be done by the hardware driver libary

Of course, you may not care about either of these, in which case rtc might be overkill and leaving it out can save you a little RAM.

RTC hardware from Adafruit

stonehippo

'''
This is an implementation of some simple, non-blocking timers for CircuitPython.
The 'timer' is just a time value and some methods to return state based on 
whatever intervals seem appropriated. It's based on adafruit_ticks and will overflow
in the same way as the underlying methods (https://docs.circuitpython.org/projects/ticks/en/latest/index.html)

Where possible, you should probably consider using asyncio. This implementation
is lightweight, but it may not produce precise results or consistent timing.

This is a re-write of some code that I originally wrote to make non-blocking

stonehippo

'''
This is a little helper for creating mock data values for a simple sensor
in CircuitPython (analogous to reading from an ADC).

It's not meant to be particulary accurate, just to create ranges of data
that might be useful when developing.
'''
from random import randint

MAX_1_BIT = 2 ** 1

stonehippo

Sources

• https://github.com/rlabbe/Kalman-and-Bayesian-Filters-in-Python
• https://www.geeksforgeeks.org/python/how-to-calculate-moving-averages-in-python/
• https://www.geeksforgeeks.org/python/kalman-filter-in-python/
• https://www.hackster.io/geehysemiconductor/visualizing-and-filtering-hc-sr04-sensor-data-on-the-apm32f4-9e3f9b

stonehippo

Storytellers RPG Solo Play Oracles

This is a Python implementation of the solo play oracles from the STORYTELLERS RPG by Candlenaut. See the solo play info, pp. 59-60, for details.

Basic Oracle

The basic oracle answers yes/no questions. The oracle rolls two d6 dice, the first designated the Yes die, and the second the No die. If the Yes die is higher than the No die, the oracle has answered "yes". It's lower, the oracle has answered "no". A tie indicates that the oracle is uncertain. The difference between Yes and No how true the response is

stonehippo

Things I've done to pretty up my terminal

• installed bat
• added $ZSH_CUSTOM/cat-alias.zsh cat="/PATH/TO/bat"
• set omz theme to bureau

stonehippo

Some Rust cross-compiling resources for Raspberry Pi

As I work on setting up a Pi Zero W as a portable system for some lightweight dev, I'm running into the challenge of compiling certain binaries on-system. To say that the Pi Zero W's resources are limited is an understatement; it can take days to compile something that might take minutes on a more robust system.

What I wanted was to cross-compile Microsoft Edit. I got it working by installing rust on my Raspberry Pi 400 with the 64-bit OS, then adding the appropriate target:

rustup target add arm-unknown-linux-gnueabihf

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CIRCUITPY_BLE_NAME="WhatsInTheBox?"

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Static Site Generators

I have a couple of projects that I am working on that I think will be ideal for a static site generator (SSG). As I evaluate my options, I'll capture some notes here.

There's a whole list of SSGs on the Jamstack site.

Standslone SSGs

• Jekyll - Ruby; one of the OG SSGs
• Blot - Javascropt (mostly) available as a service or deployed locally