GPS Locator

I often read about new Gps receiver which are so sensitive the even get a lock indoors.
Every now and then I believe this rumours buy the unit try it at home and of course it does not receive enough satellites to get a lock sometimes it does not even receive one.

A gps receiver at would be grat, I could synchronise my Rubidium oscillator with the 1pps output, or build a timeserver ,...

 The MTK3339 Gps receiver I tested has a pretty fast fix and there is a breakout pad available which fits on the Launchpad. There is even the option to connect a battery to it so it does not lose its satellite data and only needs a warm start.

When you remove the target processor on it you can use the Launchpad as serial to usb converter.
So you plug the Gps pcb on the Launchpad, start a terminal programm on the Pc and watch the Gps data flow.

Unfortunately no Gps lock at home, but nevertheless a very sensitive and fast Gps receiver.

Gps Locator pcb

Gps Locator bottom view

Links:
Booster Pack shop link
Gps receiver

Nokia 5110 Msp430 Booster Pack

Texas instruments is becoming my most used development platform.
The launchpad series is great for rapid development and did I mention the debugger is great ?
Since Ti is such a big company it is somewhat hard to gather the information you need, since they have many technical writers and thousands of documents. They also lack some kind of easy tutorial which just gets you started like the one from Embedded Artists for the Nxp line or I simply have not found it yet.

Edit:
Unbelievable there is a great tutorial site from Ti I just found it within minutes after I wrote this blog,...
http://processors.wiki.ti.com/index.php/Getting_Started_with_the_MSP430_LaunchPad_Workshop



On the other hand there is a great user community and if you have some experience with other controllers you will get used to the controller line soon.

The Nokia booster pack is designed by RobG and it is also possible to build it as a  stand alone display.
I decided to do so, but I had great difficulties to get the programmer to recognize the board.
In the end my reset controller consisting of an resistor and a capacity did not work out. After hours of head scratching guess work I removed the capacity and it did work immediately, very strange.
To program the controller I simply put the board on a launchpad with empty target controller socket.

I tried some example code from the designer and the booster pack worked great.

I usually don't like displays without a character generator,  but once you defined the character set you won't notice a difference, so no problem whatsoever.

The Nokia 5110 display is controlled via Spi bus, so update rates are fast and programming is easy once you get used to the concept. There is a nice lecture from Cornell university which helps you understand the basic concepts to use a Spi bus.

Btw. I decided to build a standalone version, because I can implement a full blown easy to use display controller module and then simply connect any circuit to it to use it, even the interface choice is flexible, from simple bit bang mode to serial or I2C anything is possible. I simply like modular approaches.

Finally some pictures:

Nokia 5110 msp430 booster pack

Bottom side

In action

On top of the launchpad to program the controller

Links:
Spi tutorial
Buy pcb from 43oh shop
Build thread

WS2812 RGB Led Matrix Booster Pack

The WS2812 is a highly interesting RGB led, since it already has a controller build in and supports daisy chaining.

Now how does it work ?
You can send 3 bytes of information to the led. Every byte corresponds to either the intensity of the colour red green or blue. 255 translates to highest intensity while 0 turns the corresponding colour of.
So f.e. you have 10 leds in a row and send 30 bytes to them. The first led grabs the first 3 bytes and passes the left 27 bytes down to the other leds. But the led not only passes the bytes down, it also reshapes the signal and amplifies it.. You don't need to worry of signal integrity.

The controller also only needs one data line, so there is no clock signal needed.

There is only one problem, the signal has to be short to get reasonable update rates.
So a 1 is translated to a 1.2us long high impulse followed by a 1.3us long low impulse.
While a 0 is translated to a 0.5us long high impulse followed by a 2. us long low impulse.

So the pulses need to be so fast you cannot bit bang them any more you need a built in hardware module.
Some genius developer on the internet suggested to use the built in Spi bus protocol since it supports fast data rates.But there are still some problems waiting to be solved. In hardware Spi a bit always has the same time frame and either a high or a low pulse.

So you have to map your bit to a matching spi sequence.
So first program the bus speed to 2 mhz. Every bit is now 0,5 us long.
A bit with value 1 now translates roughly into 11000
A bit with value 0 translates exactly into 10000

The bit with the value 1 is not exactly mapped but the processor has a tolerance of +-150 nS so we should be fine.

I tested the code with a WS2812 led light strip I built and it worked.

This is a great example of a developers ingenuity, there is a big problem but thinking out of the box and using an hardware bus protocol which has completely different specs but is fast enough saved the day.

I plan to use the led matrix  as a moodlight, but most importantly I wanted to learn how to use this leds.
I want to use them to display sensor data like temperature and humidity. Blue would translate to below comfortable, green ok and red above comfortable level.

RobG Led Matrix Msp430 Booster Pack

Backside JP1 powers module from launchpad

Booster pack in action

 Links:
Buy pcb
Designers forum thread

Meet the Powerscope

Since Ti announced the Launchpad I was very excited to play with this awesome development tool.
It is like a Arduino on steroids, mostly because of it's 16 bit capability and most important it has a debugger.
When your code does not work nothing is more useful than a debugger, maybe  with the exception of a razor sharp brain and years of development experience might not hurt either.

Since the Msp430 line supports low energy consumption and have many different feature sets it is important to verify if the consumption is really as good as it could be. To see exactly what is going on, a scope is the tool of choice, but for a quick estimation the Powerscope is much more comfortable and easier to use.

When measuring very low power devices I would not recommend to use a multimeter, because of their usualy high burden voltage. To circumvent this problem, David Jones from EEVBlog designed the uCurrent , also a great tool.
The Superprobe is a somehow similar device, but it has it's own display so you don't need to connect it to a multimeter.

I also built an usb adapter to attach the Powerscope to a Usb device and measure it's power consumption.
In the attached example pictures I connected the Powersope to an Launchpad which drove a CC2500 radio device.It does not make much sense, because the attached debugger also has a unknown power consumption but it gives an idea of usage and it also shows that the TX mode consumes about 17 mA more than the RX mode .Btw. the code in the moment has no power optimisations what so ever, I was more than happy to get the CC2500 up and running,...

The programming of the Powerscope also was more than easy.
You can either use the Launchpads programmer by removing all the jumpers and insert a programmer cable or you can like me use a Goodfet programmer designed by Travis Goodspeed.
Since I don't like to solder headers just for one time programming, I made a small programming cable with pogo pins. You can use this kind of connection even for debugging.

You can buy an empty pcb at the 43oh store.

Powerscope front side

Powerscope back side

Powerscope connected to Lauchpad in TX mode

Powerscope connected to Launchpad in RX mode

Goodfet 4_1 programmer and programming cable with pogo pins

Links:

Buy Powerscope pcb
Designer thread
Powerscope Code and Info page
Goodfet programmer