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Michael May's blog

16

Sep

2012

Not a whole lot has happened this week, I have mainly been working on assignments and studying. I have been learning a bit of Latex and I have transferred half of my interim report over but I need to spend more time working on it. Second board has been sent off to be made and components have been ordered so hopefully everything will have arrived by the end of next week.

10

Sep

2012

I have come to the conclusion that the microcontroller I have chosen is not really the best option due to the expense, size and most importantly very low stock availability. So the revision 2 board has been redesigned around a MSP430F5529, this a 80pin QFP with only 8Kb RAM, half the other one, but has enormous stock, is cheaper, and has all the same functionality except for the DACs. The smaller package means I do not have to have a major component on the bottom as I wasn't sure the radio was best suited for underneath. I have also manage to bring out more pins from the micro to a header, along with the JTAG pins. On the antenna front I found a datasheet no longer hosted by the manufacturer for the chip antenna that mentioned the gain, -8.6dBi, which is terrible. Therefore I am doing away with the chip antenna and moving to a SMA connector. This frees up more space and gives the option of using a wire just like the Skatterweb nodes. The board is complete but is being revised now and should be order sometime this week.

19

Aug

2012

Finished boards have been received from assembly and everything checks out, no problems have been detected so far. The boards have been gradually brought to life with minor hiccups in the software like forgetting the micro now controls the radio shutdown pin or the I2C address of the accelerometer has changed from prototyping with a different model.
The range has been tested to 130 meters in open space with 434MHz, 14dbm, using GFSK modulation with no manchester encoding, data rate of 2.4kbps and 36KHz deviation. I will try different configurations though.
I am also going to try to use the board as a USB CDC for displaying received data on the computer so the FTDI UART to USB converter is not needed.

30

Jul

2012

Over the last couple of weeks the schematics have been finalised and the board layout complete ready for manufacture. We're now just waiting on an assembly quote before proceeding.

16

Jul

2012

This week I have gotten the two MSP430 board communicating a simple string between each other. I have also had both I2C sensors talking on the same line and have enabled the accelerometers orientation alerting and single and double tap interrupts. The next step is to start transmitting sensor data from one to the other and test the microphone and opamp combination. I also have to confirm the micro can drive the RX/TX antenna switching lines as at the moment two GPIO ports on the radio are automatically replicating this.

09

Jul

2012

This week I have gotten the radios receiving data but it still requires a fair bit of refinement and tidying. I have yet to try communicating from the MSP430.

30

Jun

2012

This week was spent dealing with the flu whilst studying for my exam. On the 520 front, I have gotten the accelerometer working with my I2C library. Some modification was necessary as strange bug appeared when performing more than one read operation once it had been powered up and the required repeated start condition would not be sent. A work around was to reinitialise the I2C controller every operation but this is not really ideal due to the increased overhead, when I have time I will try to sort it out properly. Of the devices left to test the radio is next on my list.

24

Jun

2012

This week was spent solely on creating an I2C library for communication with the temperature sensor and accelerometer. The library is finished and the all functions of the temperature sensor have been tested. This coming week will be spent studying for my exam then it will be onto making the accelerometer work.

17

Jun

2012

This week was spent doing assignments and reports so little time for my 520 but I have done a bit more work on the schematic.

03

Jun

2012

This week has mostly been spent on assignments and tests but I have found a library for the radio modules based on a Arduino platform which I have managed to get working between two Arduinos. Now I just have to port the library to work with the MSP430 ICs which looks to just be a matter of converting the SPI code.