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ANSI Escape Sequences

Standard escape codes are prefixed with Escape:

Ctrl-Key: ^[
Octal: \033
Unicode: \u001b
Hexadecimal: \x1B
Decimal: 27

Update on Nov 30, 2025: This Gist is nearly eight years old! These instructions worked back in 2018 for the Pi 3, but recent comments suggest that they may not be sufficient on more recent Pi models and newer versions of Raspberry Pi OS. Be advised.

Using a rotary encoder as a volume control

On my RetroPie machine I wanted a hardware volume knob — the games I play use a handful of emulators, and there's no unified software interface for controlling the volume. The speakers I got for my cabinet are great, but don't have their own hardware volume knob. So with a bunch of googling and trial and error, I figured out what I need to pull this off: a rotary encoder and a daemon that listens for the signals it sends.

	typedef float mp_float_t;

	typedef struct { mp_float_t c, s; } sincos_result;

	// Compute sin and cos of (x+1)*pi/4, -1 < x < 1 to about 4.5 places
	/* polynomials from
	```py
	import numpy as np
	from numpy.polynomial.polynomial import Polynomial

	from math import sin
	import sdcardio
	import storage
	import audiobusio
	import audiocore
	import audiomixer
	import audiomp3
	import board
	import time
	import math

	# Thanks to this configuration for the initial legwork https://github.com/kbx81/esphome-configs/blob/main/dev/esp-funhouse.yaml

	esphome:
	name: funhouse
	friendly_name: Funhouse
	platformio_options:
	board_build.mcu: esp32s2
	board_build.variant: esp32s2

	esp32:

	# SPDX-FileCopyrightText: 2023 anecdata
	#
	# SPDX-License-Identifier: MIT

	import time
	import traceback
	import supervisor
	import os
	import rtc
	import espnow

	import time
	from machine import Pin, ADC, UART
	from picographics import PicoGraphics, DISPLAY_ENVIRO_PLUS
	from pimoroni import RGBLED, Button
	from breakout_bme68x import BreakoutBME68X, STATUS_HEATER_STABLE
	from pimoroni_i2c import PimoroniI2C
	from breakout_ltr559 import BreakoutLTR559
	from pms5003 import PMS5003
	import WIFI_CONFIG
	from network_manager import NetworkManager

	#include "DHT.h"
	#include "esp_wifi.h"
	#include <WiFi.h>
	#include <ArduinoJson.h>
	#include <HTTPClient.h>

	//move to secrets
	const char * networkName = "XXX";
	const char * networkPswd = "XXX";
	String AIOKey = "XXX";

	public static void Main(string[] args)
	{
	#if DEBUG
	GetJobsFromQueue();
	#else
	var host = new JobHost();
	host.RunAndBlock();
	#endif
	}

	# Be sure to chmod +x

	#!/usr/bin/env python

	import email
	import json
	import sys
	import requests

Tyeth Gundry tyeth

ANSI Escape Sequences

Using a rotary encoder as a volume control

Rotary encoder