Democracy failure

Ah well. The voting idea did not go too well. On the basis that all the pictures got an equal vote of zero I have decided to take an executive desision and choose the picture that has had most views on Flickr.

It would appear that the popularity of pictures on Flickr is based purely on how far you can see up a skirt, so I suspect that the result is slightly biased in favour of those pictures where I am showing more leg!

With sixteen views, Menacing gets it by a nose. Since that was the picture I originally posted, the one shown here is the runner up, ‘Happy’.

Suzie x

Inflorescence revisited

It is nice to be able to blog about flowers. These are the flowers on the saracenia Purpurea pitcher plant which I blogged about earlier. They are quite spectacular and quite a surprise. I should have google-image searched to find out what they were going to be like.

It is not easy to see the detail in the flowers because they are hanging down.

Suzie x

Reduction = Increase

You can spend a couple of years doing something day in and day out and think that you have got the hang of it, and then the fact that you have completely misunderstood a concept comes and bites you on the nose.

In the PIC processors, being RISC, none of the instructions are completely straightforward. This is especially the case with bit operations. You have apparently simple instructions that let you set or reset a single bit at any data location, well at least on the face of it you do! In order to keep the processors simple, pretty much all of the instructions have a structure that fits neatly into the four step pipeline of 1-load instruction, 2-read data byte, 3-modify data byte, 4-write data byte back. This same structure is underlying the bit instructions so that to set a bit, the whole byte is read, a bit is set, and the byte is written back. This works really well on memory locations where you know that what you write is what you will read back, but on I/O ports it is a different matter when the output port address is the same as the input port, and some of the input ports cannot be read in some modes!

This of course makes the process of simply turning a single port pin on or off a lot more complex than just using a bit set instruction – except that most of the time what you put on the output port gets read back in to the input port, so that as long as you don’t do something silly like short a pin or something the simple set instructions appear to work, and it has done for me pretty much up until now.

The answer as always with a RISC processor is that you have to use a few more instructions to do the simplest of tasks, and in this case you need to maintain an output buffer in memory that you apply the bitwise instructions to, before using a couple more instructions to move the buffer contents via the accumulator to the output port. In most cases the extra microsecond to do the extra instructions and the extra byte of memory won’t break the bank, but in the tight core of a PIC in a real time environment you may need a complete redesign to recover the resources.

Would it be easier in C? I don’t think so.

Extreme Trannying

I am probably breaking some tranny taboo here mentioning tree felling, but the tree about to be lopped is not a larch. It appears to be suffering, probably from over crowding, since it is a fast growing conifer. The other side is all dead where it has been shaded out by the birch so it has to go.

This photo opportunity is a result of me having a day to dress up coinciding with a request to sort the tree out before the weekend so that the area can be tidied. The outfit is not completely the same as in the other photos. Ernest Doe were not able to supply a suitable chainsaw skirt, it would appear that there is only demand for trousers and I did not think that Dotty-Pees would have anything, so I used the best thing to hand – my trusty Helium leather skirt from T. K. Maxx. The girly sized chainsaw is from Canada (it even has a French name).

I will probably be drummed out of UK-Angels now for mentioning forestry related activities but I think this qualifies as extreme trannying so I will post something to the Flickr group. Not sure yet whether it will be this one, do I look a bit too aggressive? I took quite a few pictures in the hope that one would be OK. I suspect that no-one is reading this, but if you are and want to take a look at Flickr, let me know which one you like:-

http://www-us.flickr.com/photos/suzietall/

I would have embedded the pictures in this blog, but I don’t know how to do it.

No one noticed the stiletto marks in the lawn last time, but I bet they will this time!

Suzie x

The signs of trannying

Ahh! Trannying at last I hear you cry.

Perhaps nothing to get to excited about though. I am not sure why it is, but no matter how you try and tidy up after a dressing up session, the smallest most insignificant detail that you have missed is picked up on. Here are a couple of examples:-

1. Two days after going out, having washed a lot and been to work etc, why do I here from one of the younger female members of the family. “Uncle bob, why are you wearing eyeliner?”

I looked in the mirror and I am blowed if I could see any sign of it at all, but it clearly stands out like a sore thumb to the teenage community.

2. After a short experimentation session trying to create a bit of cleavage with some gaffer tape (probably the wrong thing to use)  Mrs Suzie asks. “Have you been shaving your chest?”

“No.” I answer completely truthfully. Although the tape was hard (and painful) to remove it did not take off any hair. Again I looked in the mirror – all appeared to be present. After analysis it would appear that all that had been noticed was that some of the hairs were straighter than usual.

What hope is there for the occassional tranny!

Suzie Tall
TechnoTranny

Strange Inflorescence

The Saracenia Purpurea looks a bit scruffy at this time of year (like me!) but the new spherical flower buds are interesting. The pitchers are chock full of partially digested insects as well as a lot of other creepy crawlies such as milipedes. This plant will survive outside were it not for the birds who quickly realise what a nice source of bugs the pitchers are and then tear the plant to pieces!

Suzie x

Stripboard CAD

Laying out prototype circuits on stripboard and then documenting them is not easy to do efficiently, even with twenty five years of practice, so it is handy to find a bit of free software to do it for you.

Stripboard designer is a simple program that makes pretty documentation of your layout but does not help with the design:-

http://www.geocities.com/stripboarddesigner/

TinyCAD combined with VeeCAD can take you all the way from schematic capture to the layout of your veroboard:-

http://tinycad.sourceforge.net/index.html

http://veecad.com/

Suzie x

Budgie cage?

Normally when I am asked to fix a PC that is this dirty I refuse, but when it belongs to the family it can be harder to refuse.

The dirt is predominantly fag ash with a sprinkling of seeds from burger buns – those looking at the RSS feed will not have the picture so are spared.

It is not an ordinary PC, it is a couple of hundredweight of dual processor server with dual PSU, eight SCSI drives and a RAID controller. I thought that it would be reliable but in this case the fault was down to failure of the Mylex RAID controller card, probably due to overheating since two of the fans were completely bunged up with crud.

Suzie x

Camera train

I like model railways so a model railway does not have to be too exciting to keep my interest, but for the general viewing public at a railway exhibition the level of interest has to be much higher. Keeping trains running all the time (unlike on the real railway) helps, but any novelty that you can add is a bonus.

One thing often seen nowadays that miniature television cameras are available is the camera train, where you get to see the drivers eye view as the train is driven around the layout. Most modern locos do not have much room to install the camera, and no convienient central window, so I have decided to put the camera in a driving trailer.

The pictures show all of the bits (including the tiny TV camera). I started with an ordinary Mk3 brake coach and purchased the Hurst whitemetal conversion kit for it. It is not yet finished, still need some filling and painting, but I will keep you posted.

I took the photos and wanted to post this on Flikr tranny photo day ( http://www.flickr.com/groups/ftd/ ) but by the time I had sorted it there was not much tranny content left! Should I post it?

Suzie x

Pin multiplexing on microcontrollers

When using microcontrollers there is a lot of benefit to be gained by using the smaller ones in 8-pin-20-pin packages due to lower cost and availability in easy to use DIP packages rather than surface mount, so there is a constant striving for more efficient use of the I/O pins to minimise the need to go to a larger package.

A popular technique when driving LEDs for instance is to multiplex the outputs into columns and rows which can be very effective for a large array (for example an 8×8 array of 64 LEDs only needs 16 pins) and is well understood and easy to implement, but for a smaller array such as 2×4, the reduction in I/O from 8 pins to 6 pins is not usually worth the effort. With a bit of extra programming (which is free once you have done it) you can operate a 2×4 array of LEDs with only 5 I/O pins, which might get you out of a sticky situation and enable you to use an 8-pin device rather than have to go up to a 14-pin device.

The trick involves wiring half of the LEDs in inverse parallel with the other half and driving each set of LEDs on alternate phases of a single strobe line. This can be extended still further by driving the outputs by switching the microcontroller’s tristate output buffers on and off, allowing the I/O pins to be read when the buffers (and the LEDs) are off so that each of the LEDs can have an associated momentary switch to Vss or Vdd (which makes the LED light when pressed). With 5 I/O pins this gives 8 LEDs and 8 switches.