If you, like me, are using the excellent SCPlugin for Subversion on OS X, and also have your own Subversion server with a self-signed certificate, this thread is of interest in Getting The Damned Thing To Work™
Monthly Archive for March, 2008
An interesting appnote from Maxim, on building a rig to test the efficiency of power supplies:
Practical Data Acquisition using a Windows-based Power Meter
A neat rig all told, and shows of a few of Maxim’s cool parts, but it originally came to my attention when a former boss saw this line and felt the need to share:
"At 9600 baud, it takes more than one millisecond to transmit eight bits of data together with the start and stop bits. This is obvious in hindsight, but it can give the designer hours of undeserved enjoyment not only in wondering why data is not reaching the PC correctly, but also in illustrating the difference in operating speeds of the microprocessor and the RS-232 link."
The voice of experience rings loud and clear with that one.
This week, an appnote from Freescale on different ways to control high-brightness LEDs:
Bright Approaches to Microcontroller-Based LED Drivers
Driving these LEDs with constant current is really important for consistent results. Wavelength of the light is dependent on the current, so driving a precise value is crucial. However, forward voltage varies with current, and also experiences process variations, so the standard LED in series approach is pretty well useless if you want to control the colour of RGB LEDs properly. Thus, you need a constant current source that doesn’t depend on the forward voltage of the diode. This appnote presents a few solutions, though they head straight for the switching power supply that doesn’t work with RGB LEDs with a common supply terminal.
In Today’s lesson, we learn that if you use ls on a Linux system, and one of the directories in that directory is in fact the mount point for a Samba share on a computer that no longer exists… ls will return 1, rather than 0. If the directory is rather large, you’re not likely to notice that right off, and may suspect that someone’s rootkitted ls on your machine.
This week, from NXP, we have an appnote on building an all-software MP3 player using their LPC2148 ARM7TDMI microcontroller:
Realizing an MP3 player with the LPC2148, using libmad and EFSL
To compare: this solution uses the DAC built into the LPC2148, so it gets 10 bits of resolution for one channel. Adding an external audio DAC for a couple bucks brings that to 16 bits and two channels. The LPC2148 is running about $14 at Digikey in unit quantity right now.
Compare with the popular VLSI chips: the job is done for you, but the chips run $20 from Sparkfun, and 16 Euro from VLSI directly (!). Those prices include license fees, though, but you still need another controller to interface with your storage and get the data and commands to the codec chip. So this does have some cost benefit.
While not a company appnote per se, this document provides a decent overview of the different types of oscillators that can be used with a microcontroller. From AVRFreaks:
A bit AVR-centric, but it covers a number of useful topics, including how to properly size the loading caps on a crystal oscillator.