PIC – CatTrack

CatTrack 3.0 Minimising Current Consumption…

It’s been a couple of months without an update, but I have been busy with CatTrack. I’m currently waiting for oshpark to send back an issue 2 PCB.

The only real change from the issue 1 PCB to the issue 2 PCB is a change in voltage regulator. I have spent a long time over the last couple of weeks scalpeling my existing board and isolating everything in order to measure how much current each of the devices on the board is consuming.

I initially measured the current consumption of the whole board with everything in ‘sleep’ mode as 3.5uA. This didn’t really add up with what I expected, so I isolated each device in turn (MUCH easier said than done!) and measured the current of the PIC, RF95W and regulator seperately.

I started with the PIC. There are plenty of guides around the Internet detailing how to reduce the current consumption of a PIC to a minimum. Microchip themselves have a good guide.

CatTrack v3.0, PCBs, Posts, Schematics 4

CatTrack 3.0 Schematic, PCBs and Software!

Motivation and dedication are still high!

I’ve managed to complete the schematic and PCB, get it sent off to oshpark (my favourite PCB fab!), get them back, and solder them up, phew. I went for oshpark’s 0.8mm board thickness in order that my stacking heights would work inside the case, so they took a little longer to arrive than normal.

The schematic is below (click to enlarge). It’s quite simple and comprises the following:

Posts 8

tl;dr complete version 1 build summary

There are a lot of posts to trawl through in this blog if you’ve not followed it from the beginning. Hopefully this summary makes everything a bit clearer…

The first thing I did was to have a look at other cat tracking products on the market. I found that they all have a big flaw… battery life. I wanted GPS level accuracy and a battery life measured in months. Nothing on the market offered that, so it was down to me to design it!

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PCBs, Posts 1

Base station PCBs have arrived – time to solder!

Well, the boards actually arrived several weeks ago, but I’ve only just got round to doing the soldering. As ever, I’ve ordered all my components from Farnell in the UK.

All of the passive components I’ve used are 0402 sized (0.5mm by 1.0mm). The advantage of components this small is that you can squeeze a lot into the RF sections of the board, most notably at the output of the CC1125. This decreases board size and improves the RF performance. You can go much smaller than 0402 – 0201 is the next size down, followed by 01005 – only 0.2mm by 0.4mm! Getting decent performance out of an inductor or capacitor that small will be difficult, so it’s a tradeoff between size and performance.

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Posts, Schematics 1

CatTrack Base Station Schematic

Now that the CatTrack collar is working, I’ve been designing the schematic for the base station. The base station is the handheld unit I’m going to use to communicate with the collar to work out where the cat is. Currently I’m using a CC1125 development board. More about that here.

The idea is that the base station will mostly live at home, perhaps in my loft (to get decent range) and I’ll be able to communicate with it from my living room via Bluetooth from my laptop. It should also be portable because if Buttons goes miles I want to be able to take the base station out and about to track him remotely.

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Posts 5

Comparing compilers: CCS C and Microchip XC8

Now that I’ve got CatTrack working, I’ve been having a look at refining the code. As I previously mentioned, I am using the CCS C compiler, basically because the ‘paid for’ version of their compiler is significantly cheaper than Microchip’s XC8 ‘paid-for’ version. I did begin to wonder though, just how much bigger would my code be, and how much slower would it run if I used the free version of Microchip’s XC8 compiler?

This is what the Memory usage currently looks like in the PIC16LF18345, compiled with CCS C:

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Posts 12

It works!!!

The time has finally arrived, let’s test CatTrack on Buttons.

It doesn’t seem to bother him anyway!

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Posts, Schematics 1

CatTrack Schematic!

I’ve finally finished the CatTrack schematic, hurrah!

Click it to enlarge.

As a reminder, my plan is for the collar to work thus:

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Posts 2

Picking a GPS Module

My priority for the GPS module is the size and antenna. I’ve worked with external GPS chip antennas in the past and they can be a nightmare! Therefore for this project I’m after a small GPS module with an integrated antenna.

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Posts 2

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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