Billy Rowell williamrowell

Raspberry Pi Zero OTG Mode

Simple guide for setting up OTG modes on the Raspberry Pi Zero - By Andrew Mulholland (gbaman).

The Raspberry Pi Zero (and model A and A+) support USB On The Go, given the processor is connected directly to the USB port, unlike on the B, B+ or Pi 2 B, which goes via a USB hub.
Because of this, if setup to, the Pi can act as a USB slave instead, providing virtual serial (a terminal), virtual ethernet, virtual mass storage device (pendrive) or even other virtual devices like HID, MIDI, or act as a virtual webcam!
It is important to note that, although the model A and A+ can support being a USB slave, they are missing the ID pin (is tied to ground internally) so are unable to dynamically switch between USB master/slave mode. As such, they default to USB master mode. There is no easy way to change this right now.
It is also important to note, that a USB to UART serial adapter is not needed for any of these guides, as may be documented elsewhere across the int

IPython Notebook on an SGE cluster

This guide documents how we set up an easy workflow for using the IPython Notebook on our compute cluster managed with Sun Grid Engine (SGE).

Summary: We provide a script to the cluster users that runs qrsh to schedule an ipython notebook job using SSL and password protection.

Installing IPython

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

	#!/usr/bin/env ruby
	#
	# CLI tool for locating and removing a Homebrew installation
	# It replaces the official uninstaller, which is insufficient and often breaks
	# If files were removed, the script returns 0; otherwise it returns 1
	#
	# http://brew.sh/
	#
	# Copyright (C) 2025 Stephen C. Benner
	#

	/! normalize.css v2.1.3 \| MIT License \| git.io/normalize /

	/* ==========================================================================
	HTML5 display definitions
	========================================================================== */

	/**
	* Correct `block` display not defined in IE 8/9.
	*/

	# Make mouse useful in copy mode
	setw -g mode-mouse on

	# Allow mouse to select which pane to use
	set -g mouse-select-pane on

	# Allow mouse dragging to resize panes
	set -g mouse-resize-pane on

	# Allow mouse to select windows