1202 ALARM

I have been meaning to press my old Psion II LZ into service for a while. Now if you go way back in the blog you'll see that I was building a parallel port interface a while back for the Psion , but early tests revealed that it was painfully slow and also there were some bugs in the operation of the port, so I temporarily shelved that. Having mastered RS232 on the PIC using JAL (which is just so good I had to order the book), this opened up another avenue, communicating serially with the Psion . So here we go, the Psion II is receiving the data stream from my 16F690 A/D device and selecting one of the 8 channels to display. I experimented with displaying a bar graph on the Psion LCD, but once again, the speed was against me. I fear I may need to look at some simple assembly to achieve that one. Here's the full set-up with the Psion connected to the PIC via a (long) null modem cable, which would be spot on for connecting to my diagnostic system in the Toyota and taking...

Well after looking at the test circuit again I realised that I was using a pin on the PIC for 2 incompatible purposes, driving the RS232 communications and the enable line for the LCD display. Doh . One minor change and it is all working. I discovered a handy procedure in the JAL libraries to display a progress bar or bar graph and although I could write my own it was quicker to just use this one. Voilá , a bar chart showing the analogue value, in this case a light level detected using a light-dependent resistor. The LCD is only for testing and playing purposes, the real beef is the RS232 connection, shown here on an HP iPaq running Pocket Zeus Lite as a basic serial terminal. The PIC is programmed to output the analogue value once a second (roughly) in a standardised 8-character format of C1V0099# [C = channel; V = value (10-bit, range 0-1023); # = terminator] which can be read by anything that can understand RS232. So far only one channel is being implemented, but I'm going...

I finally got around to putting my 'new' PIC onto my new breadboard, the cool 16F690. It is very easy to rig up, only 3 external components for a minimal set-up. I wasn't sure if the Willem PCB3 programmer would work with it because the programmer is getting a bit long in the tooth, but by selecting a similar chip in the inventory it worked and I had a wonderful flashing LED. The program I wrote actually does an awful lot more than flash an LED, but that's always a good way to see something happening. Just as well because I then hooked up a 4x20 character HD 44780 display and didn't quite get what I was expecting. The display is working correctly, but the code is sending some weird characters and I suspect a timing issue, so I'll look into that. I'll sort an RS232 interface tomorrow and then we are well on the way to some tasty vehicle diagnostics.

Bit a departure this time. My wife was at a school summer fete a few weeks ago and bought our son a fossil hunting kit for a pound. Basically it was a sandstone fossil encased in light plaster with a little hammer, chisel and goggles so you could have a go at 'excavating' your fossil. Anyway, my wee fella was really taken with this and has been showing everyone his fish fossil (on the left). I mentioned this to my colleagues, one of whom studied geology at university and tipped me off to a good place about 30 minutes drive away where Jurassic fossils are easy to find. I'd never heard of this before in spite of knowing the area pretty well. One problem is that it is along a stretch of busy and fairly dangerous road where most people wouldn't bother to stop. So we set off this morning in the lashing rain, but by the time we got there it had completely dried up and we had a fun and interesting hour picking around in the rocks and came up with these fossils of ammonites and...

I finally got around to replacing the knock sensor in the MR2 last Sunday morning. The purpose of the knock sensor is to detect 'knock' in other words engine detonation and that allows the engine management to run the car with ignition advanced pretty much as far as it can go. If the sensor is faulty on the 4A- GZE engine, the 'Check' light comes on, you get error code 52 and the car goes into a safe mode with reduced performance so as not to damage the engine. The original sensor was destroyed about 8 years ago by a careless mechanic who promptly went out of business before I could get it replaced. Just as well for him because a replacement ended up costing £150. I had tried several options to get around buying a new one including trying a wide-band one and one out of a Toyota Supra. The problem is that on cars of this vintage, the knock sensor was very narrow band and tuned closely to the knock frequency which is very specific to the engine and a function of str...