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Using Palmtop GPS on a Psion 5mx … without a car!

Article written: October, 2005 by Austin Taylor

Download a copy of this article in zipped PDF format here:  (175KB)


This might not sound too difficult but, even if you were up for the challenge, why would you want to, anyway? Well, I’m sure you’ll find a reason! Actually making all the bits work together is not that difficult, once you’ve got them all, but getting the parts took me some time, as you’ll see below.

I had been intrigued by the possibilities of GPS for some time, having seen the Garmin-type waymarking devices and output in use by surveyors at the office. This is for a slightly different purpose than the in-car GPS commonly referred to as “Sat Nav” that is now all the rage. What I wanted was a sort of combination of the two ideas. Why? Well, I’ve been sold on the idea of mapping on my Psion for some time – it’s incredibly useful for finding addresses in an unfamiliar town or city (much quicker than paper maps) and I’ve had a general fascination for all types of maps since I was very young. Needless to say, I’ve got RealMaps and MapGB on my Psion as well as the planning programs I mentioned above. I’ve also downloaded many different maps, map types and map data from as many free sources that I’ve been able to find. So it was natural that, since GPS was available for the 5mx, I should try it out. I was further spurred on by Martin’s article “GPS on a netBook” but decided that the route planning approach using the Palmtop GPS receiver looked a more straightforward solution than the Garmin-style approach especially since the latter involved making up cables to join the two devices together! Martin’s approach of plugging in a CF GPS receiver won’t work with the 5mx of course, so that approach was out. So this is what I did.

First Steps – Mapping and Route Planning:

First I bought the software, Palmtop Route Planner (1998 version) and Palmtop Street Planner (1999). I later upgraded Route to the Millennium version (the newest I could find) and replaced Street with TomTom CityMaps – the last ever version available for EPOC devices dated 2001. I bought all these things on eBay, the Palmtop versions cost me about £15 each including postage, though you can sometimes get them cheaper now, while the TomTom version I got for the bargain price of only £7 including postage – probably because very few people are aware of its existence. All of this mapping software is great, though I use Route the least.

Next Steps – Get Your Hardware:

The next thing I bought was the Palmtop GPS receiver, again on eBay. These are quite rare and I had to wait a few weeks until one came up – it also cost me £65 (ouch) with Street Planner Millennium but, compared to buying any other kind of GPS on the market at the time, it’s still good value. I was eager to try it out and hooked it up as soon as it arrived. It’s a bit of a tangle of wires and I still haven’t yet forked out for an in-car holder for the 5mx, which is really needed to use it in the car, otherwise the Psion ends up loose on the front seat! But it works well and the novelty of having a moving map as I’m driving along still hasn’t worn off. It’s also interesting to see speed and check on location and other geo data as well (when parked of course). Having said all that, I thought I’d bought a dud receiver at first; I didn’t know anything about the time taken to log on to the satellite data – the acquisition rate – which can be anything up to a minute or more from cold, especially if only a few satellites are “visible”. It took me some time to appreciate what was going on and I made this fact worse for myself by trying different settings, which effectively started the acquisition process from scratch each time. Anyway, I eventually got everything working and, whilst the Palmtop device can receive signals from up to 12 satellites, not all are visible at any one time and 5-8 seems to be fairly typical – a minimum of 4 is supposedly required for an accurate fix but 3 seems to work well enough.

Real World Use - and Moving on to The Next Stage:

So I used this combination for a while but not for much more than as a gimmick because, where I live (on a Scottish Island group), serious route or street planning isn’t really an issue! And when I’m on the mainland, I tend to be without a car, so no means to power the GPS. I started to think how I could get round the power issue both for when I travel away from home but also so that I could use the set up when on foot to help in some of my other interests such as environmental data recording and in astronomy.

Power Mad:

There were two main problems to get round; firstly, the actual source of power and, secondly, how to supply it to the device. The receiver requires 0.9w at 5v dc but is supplied via a car cigarette adapter that is plugged in to a 12v output. Obviously I didn’t want to remove the adapter and fit another plug or connect the wires direct to independent batteries because I wanted to retain the option of powering the device with car battery power. Also, the adapter converts the 12v car output to a 5v input to the device and I thought that would be a useful fact because 5v is an odd voltage to be achieved with readily available batteries. I simply didn’t know how long I could expect the device to run whilst in handheld mode but thought that two 6v lantern batteries should provide sufficient power – the bigger the better, I thought because at that stage I was only taking account of the voltage, not the actual power drain.

The next problem was surprisingly simple to resolve, namely how to connect the cigarette adapter to the batteries. A quick trip to a local car spares shop resulted in my purchasing a cigarette adapter socket into which I could plug the adapter - at the other end it had crocodile clips. Initially I used the crocodile clips to attach the socket to the batteries but later removed the clips and attached the bare wires direct to the terminals – I arranged the batteries in series to achieve 12v. All worked fine first time and I was rather pleased with my achievement - so I wandered off into the garden and located myself – cool! But, in the nature of these things or, more accurately, in my nature of never being happy with what I’ve got and always looking for improvements, I decided to change things. Strictly speaking there was a very good reason to do so because the first version had one major problem; two lantern batteries weigh in at well over a kilo (nearly 2½ pounds) and take up quite a lot of space in a backpack that’s already full with lots of other equipment.

One quick call to my brother later (he’s a bit of an electrical whiz kid) and I was convinced that 8AA batteries would provide sufficient power output for the GPS device and he’d also pointed me in the direction of the necessary battery holders. I got these from RS Components on the web ( and they are RS Stock no: 594-628 “Multiple holder for 4xAA short cell” at £0.25 each. Postage to where I live incurs a surcharge so the total order of two holders cost me £6.40 delivered – not a huge outlay. I joined the terminals on the two holders together with short lengths of inner copper wire from lighting cable and the wires to the cigarette adapter socket are attached the same way – the AA batteries are retained in the holders by springs that hold these wires secure. The pair of battery holders, the short lengths of wire, the cigarette adapter socket and the 8 AA batteries are all contained within a small zippered case that was originally intended to hold spare batteries and compact flash cards but is ideal for this purpose and weighs in at just 300g (10oz) – a vast improvement. Also the case fits in a pocket or has a belt loop attachment, which is very convenient.

Real World Use – Take 2:

So how is it in use? Well, in a word, fantastic – if you’re into this kind of thing. It’s really great knowing exactly where you are as you’re zipping along on a high-speed train or flying over some European country (provided you’ve pre-loaded the appropriate maps of course). But on a more practical level its use is a bit restricted by the fact that not only do you have a power pack connected to a GPS receiver with one wire and back to the Psion with another wire, the Psion has to be open and switched on for the GPS to work. This has two implications; firstly the Psion has to be in always on mode, either using its own batteries or externally powered. To cope with this I have also acquired a car cigarette power adapter splitter that provides two sockets and a Psion car adapter. This and the GPS adapter are both powered from the AA battery pack – more wires!

The second implication is simply that the Psion5 is open. This means it is at risk from being dropped or rained on, the screen may be difficult to see in bright sunlight and it may simply be awkward to use it (especially with the pointer or trying to use the keyboard) depending on what you are doing. For example, whilst walking or using any other instrument, such as binoculars, camera etc or negotiating rough terrain or climbing over walls it can be difficult. So I tend to limit its use in these circumstances to when I’ve stopped, either to accurately record the position of, say, a plant or landscape feature or to use it to confirm my location at a place that I’m observing from (e.g. for wildlife or astronomy). The photos show me doing just that in Madrid recently.


Am I likely to use it? Yes – it’s already proved useful on a couple of trips and, whilst a bit fiddly it does what I want. Yes I could do some of these things with a Garmin device and could buy SatNav for the car but that would be the easy way – and also cost considerably more than I’ve already spent. But the only other single device that could do what I’ve managed to achieve would be another PDA platform and, frankly, having tried a variety of devices from the other platforms, none come close to being a stand-alone GPS, mapping, database, word processing, internet-enabled device that also just happens to have all my contacts, agenda, instant note-taker, voice recorder, newsreader and many others on a device that I can type and directly exchange files with my phone, my laptop and other devices without wires or conversion. A Pocket PC with a compact flash GPS receiver would certainly be neater but there’s no way that its battery would last all day in the field so perhaps that’s the real gimmick?

Shopping List:

Psion 5mx (I already had this)
Decent size Compact Flash card (this too - I use 128MB)
TomTom CityMaps Europe (£7 eBay)
Palmtop Route Planner Europe Millennium (£15 eBay)
Palmtop GPS receiver (£65 eBay)
12v Power source (8 AA batteries and battery holders £6.40), connected to…
…Cigarette lighter socket (£2.99)
In-car power supply for 5mx (£6.99 eBay)
Double cigarette lighter adapter (£3.50)
Case to carry the battery holders, batteries and cigarette lighter socket (I already had a suitable case but a small plastic food container would also suffice)

Total outlay £106.88 plus lots of thinking time and a few hours to obtain, assemble and try out all the bits and pieces – time well spent.

N.B. eBay prices are what I actually paid including postage.

Plus 8 AA batteries, say £1.99, but I already had them too!

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