Raspberry PI – What Is It

A reader commented:  “What I need as an old geezer is a practical overview of what this new stuff will do for me...”

Well, the beauty is that it is an entire computer the size of a credit card that will run Linux for $35, you can then program in almost any language, including basic.

Linux handles all the heavy lifting: file i/o, Ethernet i/o, real time interrupts, clocks and timers, etc, so you can focus on the programming.

There is a cable to bring out hardware I/O, so you can read/control anything without a lot more HW.

A LOT of bang for the buck. You can do the same on an old PC, but since it seems to be getting a lot of support in schools, there are already lots of example code and how-tos, and will be a lot more.


Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.

Raspberry PI - Looks Interesting

There seems to be a lot of interest in the new Raspberry PI single board computer, so I decided to check it out.

I am starting to see how cool they are. It is a very interesting for a $35 computer! It looks like there is a lot of critical mass developing on these, which means lots of people doing cool things with sw and hw to give lots of examples.

Looks like it is coming available again:

http://www.computerworlduk.com/news/mobile-wireless/3341734/raspberry-pis-25-pc-will-be-back-on-sale-in-a-month/?intcmp=in_article;related

They are available from this Canadian supplier, further stock expected to ship 5 Sep, 2012.

http://canada.newark.com/raspberry-pi/raspbrry-pcba/raspberry-pi-model-b-board-only/dp/83T1943?isRedirect=true

Here is a free online mag:

http://www.themagpi.com/

You can build a a multimedia box for your big screen tv...

http://www.howtogeek.com/119924/build-a-35-media-center-with-raspbmc-and-raspberry-pi/

They are also working on porting Android to it:

http://www.computerworlduk.com/news/operating-systems/3373876/android-40-being-ported-educational-raspberry-pi-pc/

You can tap into the rPI General Purpose I/O pins using something like

 this to control stuff with Python, Bash, and C programming languages:

http://log.liminastudio.com/writing/tutorials/tutorial-how-to-use-your-raspberry-pi-like-an-arduino

http://hackaday.com/2012/06/17/using-the-gpio-pins-on-a-raspberry-pi/

http://www.adafruit.com/products/914

http://www.adafruit.com/products/801

http://www.adafruit.com/category/105

Getting very interesting indeed.

 

Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.

PICAXE: Geting started

The winter of 2010/11 the local ham radio club worked on the PICAXE processor - a PIC processor combined with a free, easy to use “BASIC” like language Integrated Development Environment (IDE).

Here are some pictures of one of the meetings.

The real plus of the PICAXE system is that a very inexperienced programmer can get the canonical “led flashing” program going in a few minutes.

There are also lots of support for digital and analog I/O, timing, etc. in the language so you can build fairly complex programs quickly.

The downside of the PICAXE system is that it “hides” the details of the chips and keeps you away from the metal, so it is harder to do some more complex things that you could do in “C” or assembler.

To get started, I recommend that you get one of their starter kits like the PICAXE-08 Starter Pack to get your feet wet (blink a led, read a switch).  It is available from suppliers in many countries (i.e. PICAXE-08 Starter Pack from Canada). Note that this starter kit contains the PICAXE USB programming cable that you will need for all PICAXE projects in the future.

Note that if you have an older computer with a real old fashioned 9 (or 25 pin) serial port (or an add on serial card) you can buy this cheaper PICAXE-08 kit with a serial programming cable, or make your own PICAXE programming cable from junkbox parts (that is what I did). Also Note that the PICAXE USB programming cable is apparently just a regular USB to SERIAL cable using the FTDI 232 chip with a mini stereo connector instead of a DB9, so you could probably home brew one.

Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.

Roadtrips: Dayton Hamvention

I had always wanted to go to the Dayton Hamvention, so in May 2006 (when living in London, Ont) I went with two friends Doug Elliot VA3DAE and Andrew Mitchell VA3WAM.

"The Dayton Hamvention is an amateur radio convention (or hamfest), generally considered to be the largest hamfest in North America. It is held each May at the Hara Arena in Trotwood, Ohio near Dayton, Ohio. Hara Arena has been the home of Dayton Hamvention since 1964, but the convention has been held since the year 1952. The Hamvention offers forums, exhibit space and a flea market and usually claims to have over 20,000 visitors (verified by the ARRL). Many Amateur Radio enthusiasts go out of their way to attend the Hamvention, travelling from all over the United States,Canada, Mexico and various parts of the world and even as far as Australia, Japan and Russia." (Wikipedia)

Here are some pictures of our trip.


Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.

Presentation: Introduction to to Robotics

Here is a presentation entitled

      Introduction to Robotics

which was prepared and presented by Doug Elliott VA3DAE, Andrew Mitchell VA3WAM and
Eric Pierce VA3EP at the London Amateur Radio Club Oct 13, 2005.

In the presentation each person presents and demonstrates a Microchip PIC powered robot of their own design.

My robot is called "Skippy" (because the drive wheels are made out of "Skippy" peanut butter jar lids).  Here are some more Pictures of it. Here is the ANSI "C" source code and hardware details, it uses a Microchip PIC18F452. Note that the code is not really "finished", although it does provide a good demo of the robot capabilities, including speech synthesis with a Speakjet Chip (which is a pre-programmed PIC itself). It also provides an example of using an interrupt service routine for timing critical events. The drive motors are RC Servos modified for continuous rotation.



Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.

Presentation: Safe and Efficient Mobile Amateur Radio Operating

Here is a presentation that I did on Safe and Efficient Mobile Amateur Radio Operating at the London Amateur Radio Club May 12, 2005.


Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.

Hardware: The K8 Iambic Keyer LARC Amateur Radio Club Project

 

NOTE: The kit mentioned is NO LONGER available, this information is for Reference only.

 

At the Thursday Jan 8th Meeting Eric Pierce VA3EP presented Ham Radio Applications of PIC Single Chip Microcontrollers. At that time Eric proposed a "club project" of the single chip K8 Iambic Keyer.

 

For those who do not know, a keyer is an electronic circuit that hooks up to a morse code Iambic (dual-lever) Paddles (NOT INCLUDED with our parts kit) which automatically creates accurately timed dots when the paddle is pressed to the right, and dashes when the paddle is pressed to the left. When the paddles are squeezed together the keyer sends alternating dits and dashes (this is the iambic part). Using a paddle and electronic keyer, you can send nearly perfect code after a lot of practice. Some hams recommend never using a straight key, but to learn sending from the start with a paddle. Here is a good article on learning to send morse code with a paddle and keyer (PDF).  Read this if you are curious about the difference between Iambic Mode A and Mode B.

 

The K8 keyer that we are building also has a memory preprogrammed with your call for sending CQ, and a bunch of other features. Before going any further, download and read the K8 keyer manual  (needs PDF viewer). You will need this to operate the keyer. Note that the schematic for the keyer for our project uses an 18 pin PIC chip (not 8 pin) so our schematic is different.
 

Here is the K8 PIC 16F628A K8 source code and listing file modified for the 16F628A by Eric Pierce. (Don't worry, this is just for reference only, Eric will be programming the pic for you, so you do not even need to look at this unless you are interested).

 

K1EL 8 Iambic Keyer web page, you can read more about the keyer, for reference only you can get the source code for the keyer for the PIC 12C509A or PIC 16F84A chips.

If you purchased the complete kit, here is what you got in the ziplock bag, make sure you have all your parts before you start. (Eric still has a couple of kits available, email him if you want one):

• 16F628A PIC chip programmed with the software program, your callsign and other configuration defaults.
• 0.01 microfarad bypass capacitor
• 4.7 K ohm resistor
• 2N2222 transistor
• piezo speaker
• push button switch
• perf board
• chip socket
• battery holder and battery clip
• 1 piece scrap solid wire
• 8 pieces of scrap stranded wire

 

 

To build the kit, you need a small pair of diagonal cutters, small needle nose pliers, small tip soldering iron and fine solder. If you are not familiar with basic construction techniques and soldering, read the relevant parts of this first and practice soldering on some of your own scrap wire first.

Here is the schematic and parts pinout, top of finished board, bottom of board, details of battery holder modifications and the finished project (click each pic for larger, you probably want to print these out for reference):

 

Step by step of assembly. Note that layout is not critical, but the layout shown above and described below works ok. IF YOU SEE ANY ERRORS please email me so I can correct them.

• Mount the socket in the rows shown, with some pins bent in and others out as shown on the bottom picture. Note that the small notch in the socket goes to the end facing the holes for the puch button
• Mount the push button as shown, carefully bending over the tabs to hold it on
• Using a short piece of bare solid wire, create a "bus" on the left and right edge of the bottom of the board (push a bit of the ends of wire thru the board and bend over at top to hold them on)
• Mount the 0.01 cap and solder between the 2 busses
• Solder a bare solid wire from pin 5 to the gnd (right looking at bottom) bus
• Solder a bare solid wire from pin 14 to the positive (left looking at bottom) bus
• Solder a bare solid wire from pin 4 to the positive bus, routing as shown
• Solder an insulated solid wire from pin 13 to the top lead of the push button, routing as shown (do NOT apply too much heat to the push button, as you will melt the plastic and it won't work (yes, I did this once))
• Solder a bare solid wire from the other lead of the push button to the ground bus
• Mount the transistor as shown (make sure that it is mounted level with or below the shoulder of the switch bushing, so that it will not hit the surface the switch is mounted through) soldering the emitter to the ground bus (do NOT apply too much heat)
• Mount the 4.7K resistor as shown (note that the resistor is on the top of the board "straddles" the pin 5 to gnd wire). Solder one end to pin 6 and the other to the base of the transistor
• Strip and tin 5 short pieces of stranded wire and one at a time push through from the top of the board and solder the ends to pins 8, 10, 11 of the PIC, to the collector of the transistor and to the positive bus
• Strip and tin 3 more short pieces of stranded wire and one at a time push through from the top of the board and solder to the ground bus as shown
• Solder the black lead from the battery clip to the ground bus as shown
• Modify the battery holder by soldering a piece of stranded wire from the spring in one row to the spring in the other row as shown in the picture (NOT the rows where the clips are). This is necessary as the pic runs on 3 AA cells, not 4
• To easy in checkout, you can use bits of masking tape to mark each wire (ST pin 8, DIT pin 10, DAH pin 11, TX, +, GND, GND, GND)

Checkout:

• DOUBLE check ALL of your wiring against the layout pictures and the schematic
• DOUBLE check for shorts between pins and wires
• Carefully insert the PIC chip into the socket, orienting pin 1 as shown. Make sure that the pins are all lined up first, press very gently to get the legs started in the holes and then press home firmly. Be VERY CAREFUL to line the holes up as if you bend a pin over, you will probably break it off trying to straighten it out
• Connect the piezo speaker (by twisting the bare wires) to a wire from the ground bus and the wire from pin 8. Be CAREFUL with the wires soldered to the piezo speaker, they break off very easily (yes, I did this. I soldered it back on, but would not want to do that too many times as piezos are heat sensitive)
• Connect the wire from the positive bus to the red wire on the battery clip (you can solder a switch here during the finishing phase)
• Insert 3 fresh AA batteries into the holder (not in the slot where the wire jumper is)
• Connect the battery clip to the battery holder
• If you have done everything right, the piezo speaker should emit morse code R (di dah di). If this happens, proceed, otherwise unplug the battery and go back to the start of checkout
• Touching the wire from pin 10 to a wire from the ground bus should send dits
• Touching the wire from pin 11 to a wire from the ground bus should send dahs
• If the above step worked, press the push button very briefly, the keyer should send the default CQ message with YOUR callsign.
• Push and HOLD the push button until it emits and R (di dah dit). This is command mode where you can send commands to the keyer in morse from the paddles (which are not connected). If you wait it will get tired of waiting and send a ? (di di dah dah di di) and return to normal mode
• When done above, try this. Carefully hold the bared ends of the wires from pins 10 and 11 between your finger and thumb, with the bare ends sticking out a bit. Take the bare end of a wire from ground and place it between (but not touching) the above 2 wires. Now moving it back and forth between the other 2 wires and alternately touching and holding it to them will produce dits and dahs.
• If you can do the above, try pushing and holding the push button (with your pinky of one hand, or maybe your nose). When the keyer emits and R then send a P with the wires (di dah dah di). If you can successfully do this the keyer will enter practice mode and send random characters until the pin 10 or 11 line is grounded 
• You can test the transmitter keying circuit by connecting the cathode of an LED to the Key wire (collector of transistor), and the anode of the led to the positive bus through a 330 ohm resistor. The LED should blink when you key (but not in command or practice mode)

Finishing up the project

• Even with the tabs bent firmly, I found that the switch and circuit board wiggled a bit so I put a couple of drops of super glue around the base of the switch to make it more solid
• Solder on a mini stereo jack for the keyer to plug into, a ground wire to common, pin 10 wire to the tip (the dot (left) paddle) and pin 11 wire to ring to the dash (right) paddle
• Solder on a mini mono jack for the keying line to the TX to plug into, common to a ground wire, tip to the Key wire (collector of transistor)
• Solder a small SPST switch between the positive bus wire and the red wire from the battery holder
• Find a small METAL project box (for RF shielding) box that everything will fit into (dry fit before drilling holes to be sure)
• Drill a hole in the top of the box for the pushbutton (and attached board), the on off switch, and the 2 mini jacks
• Drill holes to let the piezo sound out
• Mount everything inside, you can mount the piezo speaker inside with small metal clips or glue
• Optionally, you might want a SPST switch in the line to the piezo speaker (just the hot lead) to turn the tone off when not wanted, or mount another jack for headphones
• If you are using the keyer with a transmitter and find that the transmitter interferes with the keyer (causes it to send extra characters, go into command mode, reset) then try bypassing the DI, DAH and Xmitter Key lines to ground with 0.01 or 0.1 microfarad capacitors, preferably at the jacks where the leads come into the box

 

Eric Pierce VA3EP - See the Disclaimer in the Introduction

© Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", 1952-2099. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Eric Pierce and "VA3EP Amateur Radio And Other Geek Pursuits", with appropriate and specific direction to the original content.