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Embedded Bits attends Embedded Linux Conference Europe

A few weeks ago the engineering team of Embedded Bits attended the Embedded Linux Conference Europe (ELCE) held this year in Düsseldorf, Germany. As described by The Linux Foundation: “The conference is the premier vendor-neutral technical conference for companies and developers using Linux in embedded products. This conference, now in it’s 8th year, has the largest collection of sessions dedicated exclusively to embedded Linux and embedded Linux developers. ELCE is embedded Linux experts talking about solutions to your embedded Linux problems. ELCE consists of 3 days of presentations, tutorials and Bird-of-a-Feather sessions.”

Attending the event provides our engineers with a valuable opportunity to keep up to date with the ever changing Linux landscape and to mix with the community shaping its future.

This year we also presented a talk titled ’12 Lessons Learnt in Boot Time Reduction’, slides for this talk are available here with videos expected to follow in due course.

Andrew Murray presenting  '12 Lessons Learnt in Boot Time Reduction' at ELCE

Andrew Murray presenting ’12 Lessons Learnt in Boot Time Reduction’

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Understanding Boot Time Variability with the Zynq ZC702

One of the challenges of boot time reduction is understanding why the boot time of a device may vary with each reboot, this is important because we strive not only for minimal boot times but for consistently minimal boot times. This post uses a Xilinx Zynq platform to demonstrate how we can measure, understand and find the causes of boot time variability. We’ll also provide an insight into how we use automation at Embedded Bits to improve the process.

To explore boot time variability we’ll be using Xilinx’s Zynq-7000 based ZC702 evaluation kit. The Zynq range of SoC’s cleverly combine a dual-core Cortex A9 MPCore with programmable logic (Artix-7 FPGA). The ZC702 is provided with a ‘Base Targeted Reference Design (TRD)‘ (a Linux distribution on an SD card) – we’ll use this to perform our investigation against.

By its very nature, the only way to measure variability is to measure the boot time over and over again during successive runs (time consuming!). At Embedded Bits where possible we install development boards into our board farm – along with providing benefits such as board sharing and collaborative working, it crucially provides automation – we’ll take advantage of this as we explore boot time variability. We’ll start by instructing the farm to repeatedly reboot the board whilst capturing boot logs.

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One Second Cold Linux Boot with OpenCV

As a means to demonstrate our boot time reduction skills, last November we put together a demo which shows an Embedded Linux device cold-booting in less than a second.

The demo consists of an ARM Cortex-A9 based device connected to a camera, 7-segment display and HDMI display. The device uses the camera along with OpenCV based software to count the number of yellow balls present on the table beneath and display the count on the 7-segment display. The device also outputs the camera image and ball detection illustration on the LCD display.

The device is able to do all this within one second of software reset, here is the video:

We’ve put lots of information on how we achieved this on our Boot Time Demos page which can be found here.

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Using ‘delay_use’ to speed up USB Enumeration

Whilst investigating ways to improve the cold boot time of embedded Linux I came across a little known control parameter of the USB stack known as ‘delay_use‘. It’s a parameter that describes the amount of time given to Mass Storage Devices to allow them to ‘settle down’ before being used. This article examines ‘delay_use’ and identifies how it may be used to reduce boot time and improve responsiveness.

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