XT-IDE adapter with CPLD v2 working

Pietja successfully built and tested our CPLD-based XT-IDE adapter v2. These boards give old XT PCs the ability to interface with IDE hard-drives and compact flash cards. There are still lots of these old boxes out there running medical and industrial equipment, and the XT-IDE cards keep them going with modern drives.

The Vintage Computer Forum’s original XT-IDE design uses discrete logic chips and all through-hole parts. Our version puts all the chips into an XC9572XL CoolRunner-II programmable logic CPLD.  We design the controller logic in software, compile it, and upload into the CPLD.

Occasionally someone finds a small hardware hack that increases XT-IDE performance.  “Chuck MOD” rewires a few traces to get a considerable speed boost for example. On the original hardware this was done by cutting and rerouting a trace with a jumper wire. We just upload a new design with the changes into the CPLD.

Our v1, 1va, 1vb XT-IDE hardware only combined a few of the logic chips into the CPLD. After testing the concept though, we moved to a 100% CPLD-based design in v2. It’s a blank canvas with an EEPROM chip that can be a disk controller, or something completely different.

The very first revision of the v2 hardware works perfectly so far.

Here’s a performance benchmark using the stock BIOS and logic:

  • Write Speed : 214,06 KB/s
  • Read Speed : 243,11 KB/s
  • 8K random, 70% read : 21,15 IOPS
  • Sector random read : 65,05 IOPS
  • Average seek, including latency, is 15,67 ms.

The XT-IDE adapter with CPLD v2a source package includes the latest hardware files and Pietja’s bitstreams for v2 and v1 adapters. We have a couple of free PCBs available to vintage hardware maintainers. Join the hacking in the forum.

A big thanks to Pietja, J1mbo, and alanh for help developing and testing the hardware. A huge thanks to members of the Vintage Computer Forums for their original design and the XTIDE universal BIOS drivers that make our hardware possible.

Serial port monitor with 2×20 LCD and 4K text buffer

Kerry uses a DIY serial display to show debugging data sent from an Arduino’s UART. Sometimes the data comes too fast to read, so he added a 4K buffer and controls to scroll thorough the history.

…if your application generates a lot of messages, it would still be hard to spot the relevant information as you can only see the last couple of lines of the data.

So my solution is to add a none-volatile off-screen buffer to the serial display so that multiple rows of data can be captured during run time and retained for later debugging.

This would be a handy tool for any serial debugging work.

Parallax Propeller encryption objects


Parallax has recently added two new encryption objects to their Propeller Object Exchange.

Mark Tillotson has released his AES object. He describes it as an “efficient implementation of the Advanced Encryption Standard in PASM. Supports 128, 192 and 256 bit keys, ECB and CBC modes. All heavy lifting in PASM.”

Mark also recently released his Secure Hash Algorithm SHA-256 object. It’s mainly written in PASM. “SHA-256 is a cryptographic hash function that maps arbitrary bit strings to a 256 bit (32 byte) hash value. This version (like many) is limited to byte strings (a multiple of an octet).”

3D Model: Bus Pirate 3.5c

Bus Pirate 3.5c is the next project we converted to a 3D model. This time we upgraded the rendering with Maxwell’s render plugin for SketchUp.

The plugin is free for resolutions of up to 800×600. First select the materials (plastic, aluminum, lacquer) for your object from the preloaded library, then start the render. It creates a photo-realistic image like the one above.

The models will be published in the Dangerous Prototypes 3D warehouse collection. They are also uploaded to our SVN. You can find them inside the “art” folders in the respective project folders. Check out the 3D view below. You can zoom and rotate the model.

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

Continue reading “3D Model: Bus Pirate 3.5c”

How long does it take to get your PCBs?

We’re writing a new tutorial on PCB manufacturing, and we’d like to include a table of approximate turn-around times for popular 2-layer PCB services. If you’ve ordered PCBs in the past we could use your help.

  • Who made the PCB?
  • How long did it take to process?
  • How long did it take to ship to you?
  • Any special notes: non-US address, non-typical finishes, etc.

We’re especially interested in the common hobby services like DorkBotPBX, BatchPCB, Seeed Studio, and Itead. Any feedback would be greatly appreciated.

Update: We could also really use (open source) images with examples of:

  • via alignment problem (drill not centered in via copper)
  • shorts (two traces under etched, still connected)
  • missing traces (over etching)

If you provide your own example image and license it CC BY-SA we’ll give you a free PCB code (first three only please).

App note: PCB design perfection starts in the CAD library

This 19 part tutorial shows how to design CAD library parts that make PCB design easier. Part one is a white paper, while the other parts are written as editorials on his blog. If you are serious about building up a part library this is definitely worth a look.

The CAD library is the starting point that affects every process from PCB layout through PCB manufacturing and assembly. There are dozens of things to consider when creating a CAD library that are often overlooked or not even considered that will directly affect the quality of the part placement, via fanout, trace routing, post processing, fabrication and assembly processes.

Via the contact form.

Free PCB Sunday: Pick your PCB

We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service.

This week we have a guest PCB, the Itead mystery pcb.  Use your coupon to pick this PCB, or any other in the free PCB drawer.

You get unlimited free PCBs now – finish one and we’ll send you another!

Don’t forget there’s free PCBs three times every week:

  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs while you wait for the weekend
  • Free PCB Sunday, right here on the blog

Continue reading “Free PCB Sunday: Pick your PCB”

App note: Noise sources in low dropout (LDO) regulators

Looking for a clean power supply for a sensitive analog circuit? Analog Devices describes the sources of noise in LDO voltage regulators, and provides some examples to limit and combat the noise.

In general, LDO noise comprises two components: intrinsic, or internally generated noise, and extrinsic, or externally generated noise.

  • Thermal and 1/f noise are the main contributors to internally generated noise and are a function of the design and semi-conductor technology of the LDO.
  • Extrinsic noise has many sources, but the most common is the noise on the input power supply to the LDO.

App note: Layout guidelines for DC/DC switching power supplies

Maxim describes how to design PCBs for DC/DC switching power supplies. Learn which traces to keep as short as possible, and the reasoning behind it.

The diagram sums up our own approach nicely as well. When working with any buck or boot converter, we:

  • Keep the main power path (shown in blue) straight and compact. We always use an extra wide trace or even a polygon. It’s surprising how often you find boards that use a dainty 16mil trace, it should be 5 to 10 times bigger.
  • Supply capacitors Cin1 and Cin2 should be as close to the switch input as possible. The switch is usually a FET, in this case it is inside the chip.
  • The buck or boost parts (L1, D, Cout) should be snuggled right up against the switch output in a straight, clean path.  The MAX16974/MAX16975/MAX16976 high-performance DC-DC converters are standard buck controllers designed for automotive applications. This application note explains how to optimize the layout of these ICs. An example layout is provided at the end of the document.

Deconstructing a retail anti theft sensor device


In this short video, Jeri and company answer the age old question: what’s inside one of those anti-theft sensor alarm devices used by the big box stores? You could call this destructive reverse engineering, or literal brute forcing. It looks like the alarm is triggered by the cutting of the attached bands surrounding the package. Possibly the sensor wire could be bypassed prior to cutting it as suggested in the video comments.

MSP430 microcontroller comparison tool

Compare Texas Instruments MSP430 microcontrollers with this online tool. Differences are highlighted in red:

This comparison engine has been developed using data found on TI homepage. As there are close to 400 types of MCUs at TI, it’s often difficult to know at once what differs form 1 CPU to another. This utility is based on TI data. It makes it easier to point out the differences by using colors. The features that differ are shown in red and the rest in black.

Via 43oh.

Pager network snifffing

Kenneth tapping a pager’s output to sniff pager traffic. He bought an old pager and was happily surprised that he could easily tap into the demodulated digital signal.

A little poking around between the circuit boards and Google and I found that this pager uses the Toshiba TA31142 FM detector specifically designed for pagers.  What luck that the datasheet was even kind enough to indicate which pin the finally demodulated FSK data was outputted on (the red emphasis in the figure above is my own).  This means that with some tricky soldering, I can take advantage of the fact that Motorola put all this effort into building a good FSK quadrature detector, and I can spend my time in the much more interesting and pleasant digital electronics land.

Adafruit has also demoed this before.

DIY MMA7455L 3-axis accelerometer breakout

Here is a DIY breakout board for the MMA7455L, an inexpensive three-axis accelerometer. It’s got all the decoupling capacitors and pull-up resistors specified by the accelerometer datasheet.There’s also an interfacing tutorial for the Arduino.

We like this chip because it’s cheap, but the LGA package is difficult to solder. If you’re not up for soldering the tiny chip, check out our assembled MMA7455L breakout board. Get the MMA7455L breakout board for $15 at Seeed Studio.

Tutorial: using Ping ultrasonic sensor with Arduino

Tronixstuff has posted a tutorial explaining how to use the Parallax Ping sensor with Arduino. The Ping is an ultrasonic distance sensor from Parallax which retails or about $30.

This segment is the latest in a series of Arduino tutorials posted by Tronixstuff.

Free PCB coupon via Facebook to 2 random commenters


Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. More PCBs via Twitter on Tuesday and the blog every Sunday.

Don’t forget there’s free PCBs three times a every week:

  • Free PCB Sunday. The classic. Every week, get free PCBs right here on the blog comments
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs while you wait for the weekend

Continue reading “Free PCB coupon via Facebook to 2 random commenters”

Week in (p)review: February 10, 2012

Here’s a summary of major developments over the last week. Free PCB Friday is coming up soon:

Coming up:

  • Free PCBs via Facebook on Friday
  • App notes on the weekend
  • Free PCB Sunday
  • New 3D model on Monday
  • Free PCBs via Twitter on Tuesday
  • Free PCB mailing how-to video
  • Weekly roundup and preview every Friday

What are you hacking this week?