Very cheap laptop.

[Dave Plowman (News)]

I'm building a Megasquirt system for the old car - this controls the ignition and fuel injection. It needs programming for the individual application - and obviously will be easier by using a laptop in the car. I've absolutely no need for a laptop now and can't see me using it for other things in the future - so I need a cheap one just for this. It needn't be a state of the art type as the software used is pretty simple. So probably something 5 years old or so would do. It must have a serial port.

Any particular make and model to look for on Ebay?

[dennis]

An elonex one and a usb serial port? New so you can use it as a real PC too. What OS do you need?

How are you measuring the exhaust gases to ensure you are still compliant with the emissions laws?

[Dave Plowman (News)]

I'm told it needs a true serial port.

Heh heh - I've just said I have no need for that. I already have a home built high spec desktop PC - for the times I need to use one. Which is rare.

I believe Windows 98 onwards.

It's an old car and the requirements are far more lax than for modern ones. But the old system way exceeded those requirements anyway at 1.5% CO at idle. The new system incorporates a lambda sensor so will have more accurate control.

[Jon Fairbairn]

In what sense? I have a little USB serial adapter, and if I plug it into a Linux machine it creates /dev/ttyUSB0 which looks like any other serial port to the rest of the operating system. From the other direction, it's a 9-pin canon D connector that seems to do all the electrical stuff a serial port does.

I've not tried plugging it into a Windows machine, but I'd expect something equivalent to happen. I suppose the other question is "what constitutes cheap?". I was going to suggest an eeepc, but the second hand prices for them don't seem all that advantageous yet. Apart from the question of price, an eeepc with the addition a USB serial port will serve as a terminal (I've checked that much).

[Andy Burns]

I have one too and it works for everything I need it for, but a lot of the SCADA software used to only run under Win98 and did direct H/W access to the serial port, so I guess it's possible the megasquirt software does something similar.

[Roger Mills]

I wouldn't have thought that make and model matter too much - as long as it has a serial port, which anything over about 6 years old probably will. Have you tried your local Freecycle? Such things are often given away in my area.

[John Rumm]

I have had mixed results with USB serial ports. One had poor drivers that caused system instability. Another worked fine - but only for some applications - alas not the one I wanted (interfacing my old Wacom tablet), a third one however worked nicely.

The tricky thing is they are all a bit non-descript, which makes buying more of the same difficult. (Having said that they are cheap enough if you order a bunch of different ones direct from Hong Kong on ebay).

[jkn]

[...]

The USB adapters (quite apart from operating system support - W98 was very poor at this) can have timing issues due to the way the USB bus works. You don't necessarily get data sent out, or received, when you expect. Depending on the protocol this can cause problems with the interconnecting equipment. I'd stick to a true serial port - as someone else suggested, an olde Elonex or viglen or something. You could probably get one for nothing if you asked - I had a use for something similar and asked on my local LUG (Linux User Group).

J^n

[John Rumm]

Old Dell latitudes are probably not a bad bet. Should be dirt cheap now. I have an old PIII 600 running Win2K that does most things well enough. They have a real serial port. Spares are still readily available.

[Peter Crosland]

It might be worth asking any independent computer shops if they have any. A bit safer than buying on eBay though you could pick up a bargain on the latter if you pick carefully.

Peter Crosland

[Man at B&Q]

It probably expects direct access to a physical serial port, which was possible in older versions of Windows.

MBQ

[Andrew Gabriel]

Many older ones have serial ports (although not all). For old laptops, the things which might bite you are: Battery life of about 10 seconds and uneconomic to replace; Screen wear or damage; Keyboard wear; Hard disk flakey; Exchangable disk drives worn out (CD/floppy).

Check it has enough memory and hard drive capacity for you. You'll probably need a set of anchient Windows disks (or the manufacturer's Windows restore disk), which the original owner should give you with the laptop.

I don't think there's anything much to choose between makes for what you want.

[Dave Plowman (News)]

I don't know, I'm afraid. Just quoting what little I've read. It might become clearer when the kit and instructions arrive.

I'd sort of hoped the way some people upgrade so frequently a half decent (in its day) secondhand laptop would be cheaper than a cheap new one.

[Dave Plowman (News)]

I have downloaded the PC part of the software and it only seems to give a choice of COM ports.

[Martin Bonner]

I suspect that when the man says "true serial port", he means it. My experience is with diagnostic software for somewhat bigger engines that the OP's (12 litre diesel engines for American trucks), but we definitely had problems with using a USB serial adaptor.

[Adrian C]

Go for something that has a few spares like batteries, screen, inverters still available on eBay. Stay miles away from things where a service manual can't be obtained.

The IBM Thinkpad T23 (Pentium III/1.13Mhz/512Mb) is a nice rugged do-anything machine ('road warrior class') for hacking around. Somewhere between £90-£120 on ebay, but a local computer shop may have one at £99

- was very popular in corporate use.

[Stephen Howard]

I'll second that...the T21/22/23 - all decent machines, as was the

570. Thinkpad parts are widely available on ebay. For a smaller laptop you could look out for a Compaq Evo N400C, though it has no built-in cd-rom drive.

Regards,

[Dave Plowman (News)]

How does it load new software without a CD ROM? Although if it has a network card I could load in what I need via the LAN.

I must admit to being surprised at the cost of an old machine - I was thinking more along the lines of 50 quid max.

[Clint Sharp]

In message , John Rumm writes

MY HP NC6120 has a real serial port I think, not checked voltages though.

[geoff]

In message , "Dave Plowman (News)" writes

Surely, it must be possible to pick one up which has been abandoned by some civil servant or other on a train or in a skip