New Horizons

Welcome to my blog

My name is Sven Andersson and I
work as a consultant in embedded
system design, implemented in ASIC
and FPGA.
In my spare time I write this blog
and I hope it will inspire others to
learn more about this fantastic field.
I live in Stockholm Sweden and have
my own company


You are welcome to contact me
and ask questions or make comments
about my blog.


New Horizons
What's new
Starting a blog
Writing a blog
Using an RSS reader

Zynq Design From Scratch
Started February 2014
1 Introduction
Changes and updates
2 Zynq-7000 All Programmable SoC
3 ZedBoard and other boards
4 Computer platform and VirtualBox
5 Installing Ubuntu
6 Fixing Ubuntu
7 Installing Vivado
8 Starting Vivado
9 Using Vivado
10 Lab 1. Create a Zynq project
11 Lab 1. Build a hardware platform
12 Lab 1. Create a software application
13 Lab 1. Connect to ZedBoard
14 Lab 1. Run a software application
15 Lab 1. Benchmarking ARM Cortex-A9
16 Lab 2. Adding a GPIO peripheral
17 Lab 2. Create a custom HDL module
18 Lab 2. Connect package pins and implement
19 Lab 2. Create a software application and configure the PL
20 Lab 2. Debugging a software application
21 Running Linux from SD card
22 Installing PetaLinux
23 Booting PetaLinux
24 Connect to ZedBoad via ethernet
25 Rebuilding the PetaLinux kernel image
26 Running a DHCP server on the host
27 Running a TFTP server on the host
28 PetaLinux boot via U-boot
29 PetaLinux application development
30 Fixing the host computer
31 Running NFS servers
32 VirtualBox seamless mode
33 Mounting guest file system using sshfs
34 PetaLinux. Setting up a web server
35 PetaLinux. Using cgi scripts
36 PetaLinux. Web enabled application
37 Convert from VirtualBox to VMware
38 Running Linaro Ubuntu on ZedBoard
39 Running Android on ZedBoard
40 Lab2. Booting from SD card and SPI flash
41 Lab2. PetaLinux board bringup
42 Lab2. Writing userspace IO device driver
43 Lab2. Hardware debugging
44 MicroZed quick start
45 Installing Vivado 2014.1
46 Lab3. Adding push buttons to our Zynq system
47 Lab3. Adding an interrupt service routine
48 Installing Ubuntu 14.04
49 Installing Vivado and Petalinux 2014.2
50 Using Vivado 2014.2
51 Upgrading to Ubuntu 14.04
52 Using Petalinux 2014.2
53 Booting from SD card and SPI flash
54 Booting Petalinux 2014.2 from SD card
55 Booting Petalinux 2014.2 from SPI flash
56 Installing Vivado 2014.3

Chipotle Verification System

EE Times Retrospective Series
It all started more than 40 years ago
My first job as an electrical engineer
The Memory (R)evolution
The Microprocessor (R)evolution

Four soft-core processors
Started January 2012
Table of contents
OpenRISC 1200
Nios II

Using the Spartan-6 LX9 MicroBoard
Started August 2011
Table of contents
Problems, fixes and solutions

FPGA Design From Scratch
Started December 2006
Table of contents
Acronyms and abbreviations

Actel FPGA design
Designing with an Actel FPGA. Part 1
Designing with an Actel FPGA. Part 2
Designing with an Actel FPGA. Part 3
Designing with an Actel FPGA. Part 4
Designing with an Actel FPGA. Part 5

A hardware designer's best friend
Zoo Design Platform

Installing Cobra Command Tool
A processor benchmark

Porting a Unix program to Mac OS X
Fixing a HyperTerminal in Mac OS X
A dream come true

Stockholm by bike

The New York City Marathon

Kittelfjall Lappland

Tour skating in Sweden and around the world
Wild skating
Tour day
Safety equipment
A look at the equipment you need
Skate maintenance
Books, photos, films and videos
Weather forecasts

38000 feet above see level
A trip to Spain
Florida the sunshine state

Photo Albums
Seaside Florida
Ronda Spain
Sevilla Spain
Cordoba Spain
Alhambra Spain
Kittelfjäll Lapland
Landsort Art Walk
Skating on thin ice

100 Power Tips for FPGA Designers

Adventures in ASIC
Computer History Museum
Design & Reuse
d9 Tech Blog
EDA Cafe
EDA DesignLine
Eli's tech Blog
FPGA Arcade
FPGA Central
FPGA developer
FPGA Journal
FPGA World
Lesley Shannon Courses
Mac 2 Ubuntu
Programmable Logic DesignLine
World of ASIC

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Friday, January 10, 2014
Tour skating in Sweden and around the world
What's New

2015-01-05 First skating tour this winter in Nacka close to Stockholm city. See the video here.

Wild skating on frozen water around Stockholm

Every winter hundreds of lakes around Stockholm will freeze and if there is no snow on the ice this is a perfect surface for skating. February 10th, 2007 was one of those days. The last week had been cold, below -10 C most of the time and no snow had fallen. On Friday evening I called and listened to the answering machine at
(Stockholms Skridskoseglarklubb) to find out about the ice conditions. It said that Lake Mälaren had frozen and that the ice looked like a mirror. You can also find out about ice conditions and coming tours from Isnytt (SSSK members only).

Every weekend during the winter if there is skateable ice, SSSK will arrange tours to the best places for skating around Stockholm. Many times you can use
public transportation
to get you to the starting point and home from the finish point. When skating in more remote places they will arrange bus transportation. These tours are only open to members but you can join as guest if know someone who is a member.


Stockholms skridskoseglarklubb
, SSSK, founded in 1901, is the largest and oldest skating association in Scandinavia and the largest skating organization outside The Netherlands. It has about 13,000 members. In the beginning, ice skate sailing dominated, but today tour skating is the main activity. Here is more information about SSSK.

Other tour organizers

You can also go wild skating together with
Friskis&Svettis and Friluftsfrämjandet or you can organize a private tour together with friends. Here you will find more tour arrangements.

Wild skating

Wild skating on ice (also called trip skating, tour skating, long-distance skating or Nordic skating, in Swedish "långfärdsskridskoåkning") is now a popular sport in Sweden. Maybe the best conditions in the world are those found around Stockholm with a considerable number of both large and small lakes plus the extensive nearby archipelago in the Baltic Sea. The smallest lakes may freeze normally in November, although the main season usually starts in December and lasts until March or April. Snow is not a major problem in this part of Sweden because in cold periods there are often areas of unfrozen water that can still freeze, and in mild periods the snow melts down to slush in the daytime and freezes to ice during the night. Watch this video (Ice is nice) to find out what it is all about.


I have collected a number of links to informations about wild skating.

Photos films and videos

Here are 
links showing you the beauty of wild skating.

Tour day

Saturday morning at 9 am all the tour skaters meet at Centralen to take a commuter train to Kungsängen a suburb North West of Stockholm close to Lake Mälaren. From the train station at Kungsängen there is a short walk to the lake and the ice. At 10 am there are about 185 people on  the ice getting ready for the tour. Now it's time to decide which group to join. You can choose between 5 groups. Group 1 is for the strongest and fittest skaters. They will cover more than 100km during one day. I went for group 3 and we gather around our tour leader for a last safety check before we leave. We are 16 expectant skaters in my group. Before we start our tour let's talk about safety.

Before you can join SSSK as a member you have to attend the "Welcome Program" where you will be introduced to SSSK and learn about ice conditions and how to skate safely. You will have two mentors (old members) who will introduce you to the club and follow you on the first tours. In this program you also have to jump in to the icy water and get out of the cut out hole using your ice claws.

Skating on natural ice is risky and safety issues are of great importance. The golden rules are never skate alone, never skate without at least one person in the group with proper experience, and never skate without safety equipment.

Safety Equipment

Safety equipment you always should have with you:

  • A floating aid. A backpack with spare clothes in waterproof bags. The backpack should have a waist belt.
  • A complete set of spare clothes. In case the ice breaks and you end up in the water.
  • Ice claws or ice-prods (Swedish "isdubbar"). These are a pair of screwdriver-like spikes. They are used to get a good grip when pulling yourself back on to the ice and they should be fastened high around your neck and secured with lines to prevent loss.
  • A whistle to attract attention.
  • An ice-pike (Swedish "ispik"). Used to check if the ice is strong enough. It looks like a heavy ski stick. Usually comes in pair and can also be used as poles when you need extra support.
  • A rescue rope in a weighted throwing bag (Swedish "r�ddningslina"). Very useful in helping to pull people out of the water.
  • To prevent injuries when falling it is also good to wear a helmet, knee and elbow protection.
After we passed the safety check the group is ready to skate out on Lake M�laren.

It is the most perfect day for a skating tour. The temperature is -10 C (14 F) and after a short time the clouds disappear and the sun shines over a mirrorlike ice field that never seems to end. The only sound you hear is the ritsch-ratsch from skates moving forward at a speed of 20 km/h (12.5 miles/h) almost without effort.

The tour leader is always in front of the group. No one is allowed to skate ahead of her/him. She or he has to decide when the ice is not safe and if we have to take another route or maybe take off the skates and walk on land. Before you can be a tour leader you have to have many years experience and  take part in the tour leader courses. The tour leader is recognized by the red SSSK flag.

After two hours of skating it is time for a lunch break. We find a sunny place along the shore  and unpack our lunch packages. This is the best time of the tour, relaxing in the sunshine with hot coffee and some good sandwiches together with a group of people you enjoy.

Tour description

Here is the tour description taken from the tour report:

Straight cross Görväln towards and through Klintsundet South of Landholmen. Crossing Näsfjärden aiming for Rönnskär,  thereafter Broknapparna, and then Lagnö reaching Ormudden - turned back - over to the other side, short walk at Färjudden to pass Ormsundet - towards Smidö, walk over Granudden to Smidösundet - first break at Lagnö before Måskär - continuing along Smidö West side - to Gullhäll, 300 m walk - East of Svalgarn - big circle North of Fagerön - then returning the same way but only a 100 m walk at Gullhäll this time - second break at Ringudden, Smidö. At Ormsundet continuing South and rounding Dävensö via Skeppsbackasundet and Norrsundet - Näsfjärden - Älghorn - Lövstafjärden - North Lambarön and finishing at Hässelby Strand.

The tour took a full  day and the sun starts to set before we reach our final aim,
Hässelby Strand from where we can take the Metro back to Stockholm City. There is always someone in the group carrying a GPS receiver to record the tour and measure the exact distance covered. The tour started at 10:10 AM and finished at 16:30 PM and was 72 km (48 miles) long and it was one of my best skating tours ever.

Tour report

Already the same evening you can read the
tour report written by the tour leader on your computer. Login to SSSKs member pages and click "Färdrapporter" and find your tour (Tokfina ytor på norra N Björkfjärden). There you will also find the tour track downloaded from one of the GPS receivers. One week later the tour report is open for non-members to read. Here are some photos from the tour.  Show tour track in Google Earth (you must have Google Earth installed in your computer).


A look at the equipment you need

First of all, a pair of skates. Touring skates (or Nordic skates) are long blades that can be attached, via bindings, to hiking or cross-country ski boots and are used for
tour skating or long distance skating on natural ice. The blades are approximately 50 cm long with a radius of curvature (or rocker) of about 25 m. The blades are about 1 mm wide, with a flat cross-section. The length of the blades makes touring skates more stable on uneven natural ice than skates with shorter blades. Since tour skating often involves walking between lakes or around unskateable sections, the fact that the blades can be easily removed from one's boots is an asset. Although mainly used for non-competitive touring, touring skates are sometimes used in marathon speed skating races on natural ice (from Wikipedia).

There are two different systems to choose from, skates with a loose heel and skates with a fixed heel. I have been skating for more than 25 years using skates with a fixed heel but after talking to people who switched to loose heel I will buy a new pair of skates with a loose heel. The loose heel skates uses the same type of binding as used on skis; Salomon
or Rottefella.


Here are some manufacturer of skates.
Manufacturer of bindings.
The boots must fit to the skates. For loose heel skates you use one type of boots and for fixed heel skates you use another type of boot.


Manufacturer of boots

The backpack acts as a lifejacket, and so needs to be firmly attached to your body by a waistbelt and leg straps, and gets its bouyancy from the sealed bags that contain the dry clothes. It should also have an outside pocket where the rescue rope can be easily reached in case of an emergency situation. Here is a
list of things you should pack (in Swedish).

Manufacturer of backpacks

Safety equipment

Ice claws                 Rescue rope                                  Ice-pikes (pair)


Whistle                                                       Knee/elbow pads           Wrist protection                         Helmet


Fully equipped

Hello, here I am fully equipped and ready for a wild skating tour. Let's go through my equipment, starting from the top.

A helmet to protect my head from injuries when falling. Will also keep my head warm.

Ice claws around my neck as high up as possible, easy to grab when in water.

A whistle attached to the ice claws. Easy to find.

carabiner (snap hook) attached to the rescue rope, placed on my shoulder so it can be easily found. Will be used to secure the rescue rope I will receive from my friends on the ice when I am in the water.

Elbow pads.

The yellow rescue rope is fixed to
waist belt of the backpack.

A pair of ice-pikes.
Used to check if the ice is strong enough. Can also be used as poles when I need extra support.

Knee pads. I use the same equipment when doing
inline skating.

Boots and skates.

A backpack firmly attached to my body
with a waist belt and leg straps.

The rescue rope throwing bag placed in an open pocket of the backpack, easy to find and easy to throw to my friends on the ice trying to rescue me.

SSSK equipment guidelines (in Swedish).

Where to skate

In the winter time there are frozen waters all over Sweden. You can use the
SSSK atlas to find a water close to where you are. There is no guarantee the ice is skateable, it can be covered by half a meter of snow but at least you know where to look. It is all in Swdish but it is easy to understand and you can show it all in Google Earth. Here is a link to M�lardalens Isguide from an article in Utemagasinet. The book P� skridskor i �stra Svealand describes 75 tours in a radius of 150 km around Stockholm. Even when all lakes are covered with deep snow you can go skating on all the plowed tracks around Stockholm.

Ice reporting

How can you find out where there is skateable ice. Here are a few places to look.

Worlds's longest plowed wild skating track

Every winter the 80 km (50 miles) wild skating race
Vikingarännet will take place between Uppsala and Stockholm (map). The start is in Skarholmen at Lake Ekoln just south of Uppsala. The finish changes depending of the ice conditions. One year it can be Hässelby, the next year Rålambshovsparken downtown Stockholm and yet another year Kungsängen. More than 2000 skaters will participate every year and they come from all over the world.

A part of this track (Vikingaslingan 60 km) will be plowed the whole winter as long as the ice is at least 15 cm thick. You can choose to start in Hässelby and skate north or start in Uppsala and skate south, it all depends on the wind. You don't have to skate the whole distance, you can stop in
Sigtuna, a small cosy town where you can have a cup of hot chocolate at Tant Bruns Kaffestuga and then take the bus back to Stockholm or Uppsala

Here is the
history of Vikingarännet.

To know where you are

When skating on large lakes or in the
Stockholm archipelago you need to bring a map and a compass. If you don't know the area you can easily get lost among all islands and narrow passages. The weather can change fast and a snow storm or fog can make it impossible to find the way without a compass or GPS.

SSSK's anniversary map (1:50 000) is a set of twelve maps covering Eastern Svealand with Lake Mälaren and the Stockholm archipelago. It is printed on synthetic paper (Tyvek) and is 100% water resistent and can be folded 1000 times without falling a part.

The Green map (Gröna kartan 1:50 000) covers all of Sweden and can be bought in book stores and in outdoor equipment stores.
Lantmäteriverket is responsible for printing all the official maps in Sweden. Here you can find out which one of the 625 maps you need.

Here are
links to places where you can find maps.

Skate maintenance

For a good skating experience it is important to have sharp blades on your skates.  At least once a year you should have them sharpened by a professional skate sharpener. But in between you can sharpened the blades
yourself using the proper sharpening stone. You can also use a hand-held Skatemate or Gnidde for a quick sharpening before you start the tour. Here is description on how to use Gnidde.

More information

Photo: Sture Homström

You are invited

Write about a subject I missed or add more information to subjects already written about. All contributions are welcomed.

Sven Andersson


Posted at 03:31 by

February 20, 2009   08:21 PM PST
Fantastic photos. Thanks
October 23, 2008   09:43 PM PDT
Hi David,

Thanks for all the information. I will add spme of the links to this page. We still have warm weather in Stockholm and no ice in sight.

April 19, 2008   02:40 PM PDT
I have added a link to HLSK on the information page. Sven
March 25, 2008   08:05 PM PDT
Hi Tony,

If you come to Stockholm next winter I promise to take you on a wild skating tour.
March 25, 2008   02:34 AM PDT
Hi, my name is Tony former Pro Hockey player living on the west coast. Just what the Dr. ordered. Ive coached and taught skating and hockey for over 25 years and Ive always wished for this before I leave this world. Just Awsome. your blessed. Tony
A Rahman
January 28, 2008   11:02 AM PST
svenand your skating quite inspiring
i m A Rahman from pakistan i had been in KTH 2 moths during 2005 but it was almost summer ending so i could not see the winter in stockholm
i also appreciate my own country mountains which are one of the highest in world
i propose u to visity lake saif ul muluk beside malka parbat(queen mountain) and lake satpara (grey water lake)in deep north of pakistan near sakardu maiin city and lake condol (eliptical lake) and so many other lakes
out of above, two i have visited
any guidance from myside welcome
Allah hafiz (God may take care u)
October 22, 2007   05:10 PM PDT
Really nice! I'm planning a trip to Stockholm just for skating on the lakes and Baltic, probably in 2009. Not enough of this in the US!
alan knowles
October 9, 2007   10:14 PM PDT
What a terrific account for a wannabe wild skater to read! Thankyou Sven-Ake. Some advice for those, like me, suffering from the intellectually crippling disease of monolingualism would be helpful in making contact with Swedish clubs.
Fingal von Sydow
February 21, 2007   04:07 PM PST
SSSK frdledare
det visste jag inte, om vderkartor

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