The core feature of OLED displays is their ability to turn off “unneeded” light sources behind subpixels – this allows them to offer a completely dark black, and furthermore save power when displaying “partial colors”.

So far, nobody has studied this phenomenon in detail – enter Jeff Sharkey. This Android engineer did just that:

Take, for example, the Nexus One. If powering only the red pixels at full intensity draws a current “i”, then powering all green pixels draws “1.5i”, and all blue pixels “2i”. (These ratios are derived from empirical measurements, and don’t hold in all cases.) Also, it’s worth noting that OLED displays don’t have backlights like LCD, meaning that darker colors draw less power.

If you could power only the red pixels you could save quite a bit of power.

So I started poking around SurfaceFlinger, the low-level window compositer on Android. I brushed off my OpenGL skills and after a few hours I had simple proof-of-concept. A couple hours later I had several filters between red-only and full-color:

Even though I am not sure whether anyone of you is willing to give up color display in exchange for longer battery life, hit the URL below to see his amazing numbers and a bunch of photographs:

Dallas Maxim has posted yet another highly useful application note to its website – application note 4029 looks at accessing smart cards(the cards used in banks,…).

While the text is a bit biased towards Dallas Maxim products(hey, its an application note); it nevertheless gives an excellent overview of the communications protocol used to communicate with smart cards. In case you feel like tinkering around, get the full scoop here:
The DS8007 and Smart Card Interface Fundamentals

P.s. TamsPalm denies all responsibility should this information be used for fraudulent purposes. In other words, folks, don’t get yourself into jail by hacking around with credit cards :)

Light Emitting Diodes, abbrev. LED’s, are up-and-coming and will eventually replace both classic light bulbs and CCFL’s in various applications. TamsPalm covered a LED-powered Jornada a few months ago – meanwhile, LED’s have gone main-stream; with the latest ipaq’s having LED backlighted screens.

National Semiconductor has released a paper that looks at driving high-power LED’s a few days ago – while it does contain a nasty bit of advertising, parts of it make an excellent read(especially for all those who wish to create a LED-powered IIIc :-) ):

Classic voltage regulators like the 78xx series can be integrated into a circuit easily, however, their energy efficiency is terrible. Getting out higher currents at a high voltage drop makes these IC’s behave like mini stoves; and getting them to increase output voltage is impossible – not the kind of behavior needed when creating a circuit for a battery-powered device like our ever-famous Meazura(even though it can source an insane amount of current).

Switching converters address both of the problems outlined above, offering extremely high efficiency and being able to amplify voltages – however, these features come at the cost of increased complexity.

Dallas Maxim has an excellent application note covering the theory behind SMPS’s – enjoy:

Finding out the communication protocol for communicating with SD cards is not easy – the specification is not available for free, and relies on a proprietary 6-wire bus. However, SD cards can also be accessed via SPI…and this is what the following application note from Dallas Maxim covers:

It starts of by looking at the electrical interface and goes on to the actual communication protocol, covering special commands, speed limits and other interesting stuff.

If you ever need to use an SD card in a device you built yourself, start your research here…it will pay out!

After having looked at the Aceeca Meazura developer module a few days ago, vivomobile sent us even more Meazura goodness…aka developer module endcaps. These endcaps allow you to “cover up” your developer module and seal the Meazura back to its waterproof state. vivomobile sent us two kinds of endcaps – read on to find out more:

Normal endcap
0a Aceeca Meazura developer module endcaps 0b Aceeca Meazura developer module endcaps

The normal endcap simply gets screwed on the top of your rev6a module. You can then screw the module into a Meazura as if it were a CF module – waterproofness et al…

Wire endcap
1a Aceeca Meazura developer module endcaps 1b Aceeca Meazura developer module endcaps

The wire endcap usually ships with a set of three cords that can be plugged into the ports at the top of the module. You can then solder a rev6a board to the back of the cap(solder the gold pins onto the rev6a module):
2a Aceeca Meazura developer module endcaps

This gives you a waterproof Meazura – and the capability to route signals out of the machine!

Overall, I still like my own custom way of building circuits best(pictures coming soon). However, Aceeca really does think about its designers…if you still have any questions, feel free to post away – Aceeca reads TamsPalm(and vivo does, too)!

When building circuits, many peripherals accept data via a serial, RS232-style connection. Cheap micro controllers(e.g. PIC16F84A) don’t have an internal UART though…”bit banging” a port is due.

Dallas Maxim has published an application note on how to implement a software UART on one of its MAX controllers; but the information is also useful for most other controller types.

I needed sth like this a few weeks ago…enjoy:

Aceeca’s Meazura is especially interesting because of its MZIO slot that allows hardware to be added without significant effort. Aceeca has created a lowcost developer module to simplify development…and vivomobile sent us a few free samples.

When you first get your developer module(pictured below), you will probably feel overwhelmed by the plethora of contacts and connectors. But fear not – the TamsPalm team is here to help!
DSC05750 Making sense of the Aceeca Rev6a dev module DSC05748 Making sense of the Aceeca Rev6a dev module

Basically, your module consists of three separate PCB’s as shown below. The ‘main’ PCB contains the soldering isles where you connect to the bus. The side PCB usually mates with connectors…but these aren’t present on the cheaper(I prefer this one to the one with endcap) version. Instead, you can route wires through the holes. The IR PCB is completely useless most of the time…it just contains the IR transmitter:
mod Making sense of the Aceeca Rev6a dev module

Essentially, you solder wires to the main PCB and route them outta the holes to your circuit. However, there are a few FAQ’s which are answered below:

Is the IR board always connected to the Meazura
Yes. The signal path is shown by the arrows in the figure above…you can easily trace them on your board. As long as the circuit you build doesn’t interfere with the Meazura’s UART2, the IR system will work like it would with any other module.

Is there any kind of protection for the Meazura on the board
No. 5V or a short circuit…and the Meazura is done for…

Is the Meazura waterproof with the board installed
Nope! Treat a Meazura with a dev module inside like a Palm IIIc or a similar, very sensitive handheld…

If you have a burning question, just post a comment and get it answered!

I wanted to access a SD memory card with a PIC microcontroller a long time ago, but did not find a howto or even just information on the SD card’s specification anywhere. The guys at Dallas Maxim’s have figured out a way to access SD cards without implementing the SD protocol – after all, MMC and SD cards are somewhat compatible, and MMC cards can be accessed via SPI.

The application note below looks at interfacing a MAXQ controller to a SD card – but it can easily be adapted to other controllers:


When one wants to get back into breadboarding circuits, nothing is beter than having a collection of working circuits to get back on track. Obviously, your own ones are the best – but since most of my documentation was distroyed a few years ago, this sadly is no option for me.

Tony van Roon has gateherd up a load of sample circuits here – enjoy:
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When you have built a nice circuit, the bigst problem is how to create an “UI” for it that everyone can use – I can still recall my Micro Power Converter – it was 2.5cm^2 big, but no one could use it but me; and even I needed a control voltmeter and a screw driver.

Jakob Selbing ripped apart an old Nokia cellphone and found out that the PCB works well as an input/output terminal – enjoy!
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Dallas Maxim seems to be at it again – this time, their latest application note covers adding a resistor across a linear regulator to “boost” its maximum output current:

Little to add here…

Many owners of vintahe (Palm powered) handhelds know the problem – the first-gen color TFT screens like the one used on the Palm IIIc tend to develop a pinkish hue as they grow older and the gas mixture in the lamp degrades.

An anonymous Jornada owner(those Windows CE powered keyboard organizers, no Palm OS on there) now replaced the CCFL in his machine with a bar of white LED’s and describes the process on his web site:

While I don’t feel like trying this out right now, it definitely is an impressive idea to fix my Palm IIIc if it finally goes pink!

People who read TamsPalm for a long time probably already know that I am very fond of Dallas Maxim and their marketing/marcomm methodologies. The methods used are extremely cheap, but terribly effective.

Dallas Maxim sent me the latest issue of their A/D Converter design guide today. A design guide is a document that intorduces you to cool Dallas Maxim devices – and this one really contains parts that I dreamed off when still doing electronics two years ago:

By the way, Dallas Maxim offers free samples!

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