Posts 3 comments on PCBs have arrived! Soldering and matching the antenna…

PCBs have arrived! Soldering and matching the antenna…

The PCBs have arrived from OSH Park!  As expected, they look good and the quality is excellent.  As an added bonus, they even fit in the case I designed them for.  Result!

Over the last couple of weeks I have also been ordering all the components from a combination of Farnell and tme.  Everything’s arrived and it’s all ready to solder into place.  I’ve also got the firmware into a state such that something should work too.

Now it’s time to get soldering!

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by andyc
Posts 8 comments on Writing the Code

Writing the Code

Whilst I wait for the PCB to arrive I can crack on with writing the code that’s going to run on the PIC.  I’ll write it in C (not assembler…!), using the MPLAB X IDE and the CCS C compiler.  I much prefer the old MPLAB 8 IDE, but Microchip has stopped supporting new devices in version 8, so I’m left with no choice but to use MPLAB X.  It’s all very pretty and I’m sure I’ll get used to it…soon.

I’ve chosen to use the CCS C compiler over Microchip’s C compiler basically because of cost.  Although Microchip have a free version of their XC compiler, all of the optimisations are disabled.  This results in terribly compiled code which takes up much more space than it needs to.  Not ideal for a small embedded device with limited storage like I am using!

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by andyc
Posts 2 comments on One last thing…. The Antenna!

One last thing…. The Antenna!

I was a little premature with my previous post.  I can’t quite draw the schematic diagram yet – I need to work out the antenna!

Texas Instruments have produced an excellent guide, examining a number of different types of antenna for embedded applications.  The table below summarises the pros and cons of a number of different antenna solutions and is taken from that guide.

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by andyc
Posts 5 comments on Choosing a Power Source

Choosing a Power Source

The last thing I need to work out before getting on with the schematic is which battery chemistry I’m going to use.  The most important thing at this point isn’t necessarily identifying the exact battery I want to use, I need to just know the voltage, such that I can design the circuit to suit.

In order to work out the ideal battery chemistry, I need to work out how much each component draws, both in sleep mode and at its peak.

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by andyc
Posts 2 comments on Choosing a Microcontroller

Choosing a Microcontroller

We’re having a bit of a heat-wave at the minute in the UK!  It has been over 30°C (86°F) for 2 days in a row.  We can’t cope.  It’s too hot.  Buttons particularly is not impressed.  The coolest place he’s found is on top of the water butt – as you can see in the picture.

Anyway, as everyone knows, the best thing to do when it’s nice and sunny outside is sit inside on a computer and look at Microcontrollers.

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by andyc