Sep 19

My Custom HP Logic Analyzer 16700A Cart

So after looking at the high priced real HP logic analyzer cart that didn’t look that great to me, I decided to build my own incorporating a ton of features that just really makes my life easier. This is optimized for use over cost.

The physical make up

  • It uses solid 2×2 poplar posts as the overall frame. Easily available from Home Depot.
  • The surface is 3/4″ birch veneered plywood. I use this plywood for a bunch of projects. It’s pretty solid stuff, and the birch really looks nice on top.
  • The surface is treated with Polycrylic. Polycrylic resists damage from abrasion, scuffing, chipping, water, alcohol and other common household chemicals. This is nice stuff, but expensive. Nice topcoat.
  • The visible layered plywood sides were wrapped with birch veneer that I ironed on with a clothes iron.
  • The overall dimensions are 24″ Wide, 27″ Deep, 35″ High including the 4″ high Casters.
  • This thing is built like a brick shithouse. Even with the Heavy LA on it, it’s really sturdy.


Labeled Features

  1. The monitor is a 20″ 4:3 Samsung. It was an older one, but that’s exactly what I wanted. I don’t think it will do the 1600×1200 max resolution, but the next one down (1280 x 1024?) It’s connected to an Ergotron(love this company’s stuff) monitor arm so that I can push/pull/adjust/spin/raise the monitor over top of DUT’s.
  2. This is a 115 watts of light DIY flexible task lamp that I built myself out of spare strip LEDs. It uses less than 20 watts of power. Look here if you’d like to see the full design for it. It works very nicely.
  3. The static dissipative naprene rubber mat from 3M 8831 is beautiful. It’s a great tough surface that really works. I have a wrist-strap (w/ 1M resistor) attached to the corner. The mat is fully grounded through the power strip on the rear.
  4. This custom sliding keyboard shelf is almost 20″ wide and includes a Cherry ML4100 keyboard that is compatible with the LA. I also added a Kensington trackball M01082 which is much more practical given the space limitations. I like this solution better than trying to jam a full-sized keyboard in there. The shelf was put at an ergonomic height.
  5. This is the HP LA itself. Right now, it’s outfitted with a 16752A, (2) 16715A’s, (2) 16717A’s.
  6. I found a generic storage bin that really fit the space underneath the cart. Perfect dimensions. I use it for storing cables, CDs, manuals, and everything related. Nice to have it all in one place.
  7. These are 4″ Black 4″ Black locking Polyolefin Wheels, model L3PB4X. Support up to 250 pounds. I originally used 2″ casters, these are so much better.

Other things that are nice to have

  • A 12-outlet Belkin Surge Suppressor with a 10-foot cord. This is nice because everything attaches to the strip which is zip-tied to the frame, and then just one cord leaves the cart to the outlet. This means I can wheel this thing around my make-shift lab and have it exactly where I want with minimal mess.
  • A wireless bridge that connects the wired RJ45 network port to 802.11 wifi. The brand is IOGEAR, and it simply does the job beautifully. This prevents me from running an ethernet cable over to the LA.
Aug 02

My new i7-4790k Desktop build


I needed some more horsepower for my FPGA compiles, and because it’s been so long since my last PC build, I decided to take advantage of some free time I had, and build a new machine.

This machine is a quad-core i7 build with 32GB of DDR3 and (2) 240GB SSDs.

PCPartPicker part list:
Price breakdown by merchant:

CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor  ($279.99 @ Micro Center)
CPU Cooler: Noctua NH-C12P SE14 65.0 CFM CPU Cooler  ($63.97 @ OutletPC)
Motherboard: Gigabyte GA-Z97X-Gaming 5 ATX LGA1150 Motherboard  ($129.99 @ B&H)
Memory: (2) G.Skill Sniper Series 16GB (2 x 8GB) DDR3-1866 Memory  ($104.78 @ OutletPC)
Storage: (2) Sandisk Extreme Pro 240GB 2.5″ Solid State Drive  ($129.88 @ OutletPC)
Video Card: Gigabyte GeForce GTX 750 Ti 2GB WINDFORCE Video Card  ($109.99 @ Newegg)
Case: Corsair SPEC-03 Red ATX Mid Tower Case  ($69.99 @ Newegg)
Power Supply: Rosewill 500W 80+ Gold Certified Semi-Modular ATX Power Supply  ($69.99 @ Amazon)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer  ($18.75 @ OutletPC)

Here are some photos from the build, enjoy!

nerdporn justcpu finished_outside finished_closeup cpu_wpaste before_cpu_fan

Jul 15

Memory controllers in FPGAs are the bane of my existence, help needed

I want to put together a softcore 68K computer system, just something simple.

I’ve purchased, but not yet received, the Terasic Cyclone V GX Starter Kit, an Altera FPGA eval board.

It looks pretty sweet and includes some fun stuff I’ve never done like HDMI connectors, has some easy to access onboard SRAM, has built in FTDI USB support, built in programmer, built-in flash for non-volatile storage, 77K logic elements, and the list goes on.  Looks like a really sweet board EXCEPT for one line on the datasheet:

4Gb LPDDR2 x32 bits data bus

“Oh no! Not yet a different memory chip or interface”

What’s nice is that there are (2) HARD memory controllers built-in to the FPGA, and so you don’t have to waste logic elements for defining your own. While I’m not sure what I was thinking, I really expected the interface to the memory to be very simple…. You know something like a FIFO-front end where you’d specific address, read/write, data, and then throw some read_data_valid switch and voila. Well, of course, I’m wrong.

Again, I’m in the middle of a memory controller nightmare.

For my Altera DE0, I modified the memory controller found here. It works like a champ, and the interface is pretty darn simple.

I could really use some help putting together a simple to use DDR2 controller to access this chip:

MT42L128M32D1LF-25 WT

It’s configured like this: 16 Meg x 32 x 8 banks x 1 die. Rows are addressed like this “16K (A[13:0])” and columns “1K (A[9:0])” using Single Channel Addressing. Cycle Time is “-25 = 2.5ns, tCK RL = 6”

What I don’t know is whether I can even start with a SDRAM controller and then expand on that, or if a completely different approach is warranted. I know that DDR2 is still SDRAM, and the interface to the new memory chip is very similar. I don’t really need the double-pumping or the increased data rate — I’d take anything to get off the ground.

Ideally, I’d find a verilog module for a controller with an example module that instantiates it, writes to some addresses, and then reads them back and verifies them.

A google search, as well as investigation on OpenCores hasn’t yielded much. This Altera youtube video is promising, but it stopped short on showing the HDL-specific details on how to instantiate it, and how to actually USE the module that gets created. This is assuming that everything goes swimmingly during the fairly complicated MegaWizard process.

If you’ve got any experience or helpful tips, I’d appreciate it.

Jun 26

$28 Gonbes GBS8200 Scandoubler for use with Commodore Amiga


While I probably would have preferred to order an Indivision ECS scan doubler, a really nice alternative is a Gonbes GBS8200 video converter off of ebay. I had bought version 2.0 sometime in 2010 or 2011, and could not make it work in any fashion. I think, at the time, the limitation was the ability to handle a combined horizontal and vertical (composite) sync signal at a low refresh rate ~15khz, like the Amiga puts out.

I decided to try a new version, version 4.0, from the first quarter of 2014. I bought this on ebay for $28.00 shipped which is an awesome deal. I received the board three days later in the mail, which is impressive for free shipping!

Here’s the ebay item number and description in the case where the number will change:

Genuine Gonbes GBS8200 CGA/EGA/YUV/RGB To VGA Arcade Game Video Converter Latest

Luckily, I already had “stock” at my house of DB23F connectors, and I’m glad I bought some extra when I did. It seems there are still some sources around (in mid-2015) for some connectors, although prices seem to be going up. Worst case, you could hack an existing cable, or buy a replacement video cable off ebay, and use that.

For pinouts, you only have to connect (5) wires to get this working:

DB23 pin to VGA converter wire color

3 to RED

4 to GREEN

5 to BLUE

10 to GRAY (Composite Sync signal)

16 to BLACK (GND)

When the video converter powers up, press DOWN/AUTO button to get the unit to sync up. You may need to modify the horizontal position(I needed X position: 57) or adjust the zoom.

My unit powered up in Chinese. You need to select option 4 (bottom option) for language, and then choose English on the next menu.


I powered this with my Rigol DP832 power supply and measured the current draw at various voltages. Note that you should NOT power this thing off of the Amiga’s DB23 video port. It simply can’t support the current draw.

Current draw in idle mode(no video): uses about 1.6 watts or +12v 133ma, +8.5v 180ma, +5v 300ma

Current Draw in active mode: uses about 2.4 watts or +12v 200ma, +8.5v 276ma, +5v 468ma.

So if you use a +5v regulated power supply, you need to be at least 625ma if you wanted a 25% safety margin. A 1 amp supply would probably be better. Note that the official specs call for 2 amps of current at +5v. My field testing doesn’t really prove that number out. I’ll keep it running for awhile, maybe something goofy happens like as it heats up, it draws more current, or something.

This blog here helped me, but remember, it’s not safe to power it off the video port!

Update: I’ve tested this on two different models, a Widescreen Samsung S22C300 monitor, and an older square Samsung SyncMaster 204B.

May 26

DIY 115 watt flexible LED Task Lamp


ledtask_headSo I wanted a very bright flexible LED task Lamp that didn’t break the budget. I had a few feet of 7020 LED strip lighting left over from my undershelf LED lights, so I decided to put those to the task. These LEDs give off about 33-35 lumen per LED, and I’m using 54 LEDs for the task. That’s about 1836 lumen which translates to roughly 115 watts of light. The best part is that it’s very efficient, only using under 20 watts of power, including power supply losses, measured by kill-a-watt.

Shopping list:

  • 120mm x 100mm x 18mm Heat Sink: The mounting base for the LEDs is an aluminum heat sink. All these LEDs give off a bunch of heat in a small space, so a heat sink is crucial. While I could have done the thermal calculations to determine exactly which heat sink to buy, I had a hard time even finding a suitable size and shape of heat sink I wanted, that could be delivered in a reasonable time frame. $12 prime-shipped.
  • The 7020 LED strip lights from ebay and China: These things are freakin’ awesome. Really bright, really easy to use. You power them with +12v using a regular off the shelf adapter. The LEDs feature a positive and negative rail that runs down the length of the super flexible PCB. They include adhesive on the back. $23 for (16) feet of the stuff shipped from China, via the slow boat, seriously.
  • 18″ flexible gooseneck and desk clamp: I could have ordered a 24″ for just about the same price, and I think that would have been the better choice. This gooseneck is really high quality and the stiffness makes me think it will last a long time before I need to replace it. This is NOT the cheap quality stuff you get on IKEA/Walmart/Target lamps. This company’s website is a little hokey and my order errored out the first time I placed it. About $32 plus shipping is fixed around $13 for the two items, which is sort of ridic, but whatever. The most expensive part of the lamp.
  • A cheap 12v power supply: Provides +12v at 5 amp which is more than enough. This lamp only draws about 1.3 amps, so you could get something smaller. $8 prime-shipped.

 Installation Notes:

  • Notice that there is a positive and negative rail that runs lengthwise down the strip. On one side, notice that I cut the negative rail short, and on the other side, I cut the positive rail short. This is so I could run my own power bus straight down and connect all the strips together. +12v rail on one side, GND on the other.
  • Both the center of the strips and the edges are insulated off of the aluminum heat sink. While there is some separation with the adhesive, I wanted to make sure this stuff didn’t short!
  • I used a smaller stranded wire (24 gauge) to connect the strips but only for 6 or 7 inches. I convert quickly to 18 gauge which should be much more sufficient.
  • I used heat shrink tubing extensively to add better protection for the wires.
  • I drilled a 3/8″ hole in the bottom of the heatsink to mount the gooseneck. The gooseneck didn’t have much metal to “grab” so I used two different JBWELD products. Their stuff is awesome. I used SteelStik (soft, flexible, steel-fiber, epoxy putty) to form a top cap. I also used their ClearWeld at the base of heatsink which rests on the top lip of the gooseneck. Is this overkill? Probably. Will this connection break in my lifetime, almost certainly not! See pictures below.
  • I added an inline switch to the AC side of the power supply figure-8 cable.
  • These LEDs are on the blue end of the spectrum and produce a very very white light. This is completely different from Incandescent light, and you if you photograph under it, make sure to adjust your white balance accordingly.
  • I’ve made a huge leap of faith with this heat sink. I could be entirely underestimating the amount of heat dissipation required. I can tell you that after an hour of running, some parts of the LEDs are close to their maximum operating temperature(170F), while the rear of the heatsink (average temperature) is around 85F. The fins are much hotter.


May 03

migrated website to a new host

Over the last week, I migrated this blog to a new hosting provider. GoDaddy was such a pig and the site just ran like molasses when hosted by them. I couldn’t be happier with the switch that I’ve made, but I could very well have broke something that I haven’t realized yet. If there were resources that you were using but are no longer available, please leave a comment, and I’ll fix them up.



Apr 25

Reading Amiga Kickstart ROMs with a TL866A reader

I recently bought a TL866A from ebay with a bunch of adapters for a little under $100 shipped. Seems like a decent programmer except for the fact that it doesn’t support the 27C200/27C400 mask ROMs that hold Kickstart. Some alternatives floating around seemed to indicate that the 27C240 was pretty close, but the pinout was different.

I created an adapter to convert the pinouts.

The parts I used were:

While I love Emulation Technology’s stuff, their shit is never in-stock and it’s always so damn expensive. They make a $93 adapter for just this purpose, and thankfully provide the pinout. I downloaded the datasheets for the two ROM chips, and came up with exactly what they did, so I used theirs as the source for the pinout.(PDF linked datasheet). Local Pinout if their link goes down.

Here’s the finished result. Lots of patience was required to wire-wrap this. (80) connections is no joke!



In Minipro, the TL866A programmer software, I selected “INTEL 27C240” and this seemed to work, although “Check ID” feature didn’t work, because the chip is identifying itself as something different.



I still want to compare my read with some other files, and check that it worked 100%, but the initial results look fine to me!

A couple things to note:

  • I’m not focusing on whether I can BURN 27C200/400’s yet, I just wanted to read them. I’d THINK this would work, but this would need verified before I’d try it.
  • There is a reverse problem that would require a different solution, and that is using newer/alternative roms IN THE AMIGA ROM SOCKET. Remember, this adapts the amiga rom chip to be readable in the programmer. Nothing more!!

Update: I verified my ROM read 100% correct by comparing the CRC32 checksum to one on the Cloanto ROMS page found here.

Apr 18

Update to Rigol CSV to OLS file conversion post

A couple years ago I posted some information on how to convert a Rigol CSV to an OLS File.

I recently got a request for some more information.

So let’s look at the two files

First twenty lines of the Rigol CSV


First twenty lines of the OLS ouput file

;Rate: 100000000
;channels: 16

So you should be able to visibly see the differences without even looking at the specs

  • Headers are different
  • Rigol has a time stamp as the first column of the CSV (relative to the trigger point)
  • Rigol has comma-separated columns
  • OLS has an “@<samplenumber> at the end

So as you can see, this is a simply moving text around and putting it in the right place. Linux is especially suited to these types of tasks, which is why I chose it over Windows. Right OS for the right job. There’s no perfect OS.

Linux is suited because of it’s excellent set of individual tools that can be chained together using pipes to achieve multiple transformations, all on the same line.

So let’s look at the linux commands and “take it apaaaaaarrrt.” (for you eevblog’ers)

cat NewFile0.csv: Use the NewFile0.csv as the starting point aka input file, let’s look at one line at time.

cut -d , -f 2,3 -s: Use a comma to delineate the columns, and output just columns 2 and 3 (ie the high order byte, and low order byte). The “-s” tells us to not include lines not containing commas.

nawk ‘{print $0″@”FNR}’: This gets us the “@” sample number, which is just a constantly increasing number.

tr -d ‘\r’ | tr -d ‘,’: Remove the carriage returns, and the still remaining commas produced from the “cut” above.

sed -e “s/ 0/00/” >NewFile0.ols: Replace ‘ 0′ with ’00’ because that’s how OLS needs them. Output the results to a file called .ols. The space before the first zero is very important because it could modify other lines unintentionally!

Example without the “sed” above: “3e 0@662
Example with:”3e00@662

I welcome comments below!



Mar 24

Commodore Amiga Floppy Analyzer


So I’ve toyed with the idea for quite some time about having a tool that was a little more “data” centric for analyzing floppy data. The Amiga Floppy Project Nostalgia client(which was the main Java client for the project) had fairly limited analysis capabilities. It was more ADF-generation tool than anything.

So I spent a couple nights on slapping something together, and this is what it looks like.

It does a bunch of things:

  • The input file is a “Delta T” file which contains time between pulses which are nominally 4us, 6us, and 8us for a LD amiga floppy. This can be generated a bunch of ways.
  • It identifies in range and out range values.
  • It plots all the values in the file on the top chart. Ideally, a really clean floppy read will have three distinct bands. I call these bands clusters. It shouldn’t have many values (outside of the track gap) far from the center line.
  • It locates these starting and ending boundary for each cluster using an adaptive read algorithm which removes things like motor speed variation from being an issue. It automatically adjusts the reading based on the form of the data!
  • It calculates an average for each cluster and displays it as a horizontal red-line on the graph.
  • It finds the magic 0x44894489 sync value and plots it as a green vertical line. Those are the start lines of each sector.
  • The top graph functions as a way to look at all ~50k delta T values and spot the outliers.
  • Next, bottom left, it plots a histogram showing the number of values in each cluster.
  • The bottom center has a text output display that gives cold hard numbers and resulting analysis like standard deviation for each cluster. Lower standard deviation values means a cleaner disk.
  • It decodes MFM using the adaptive cluster boundaries, and then calculates header checksums and datachecksums.
  • It performs (6) different tests on the data and you receive a bright green checkmark if all PASS.
  • If there’s a corrupted sector, then you can drill down into each sector


The above example shows you that Sector 5 is bad, clicking the RED sector number takes you here


Where now your presented with a hex editor, and a copy of the Delta T’s restricted to just that sector.

Now I have very little time so far put into this application, and so it’s not even close to be ready for more-than-me consumption. Things that need to be done are:

  • It handles one track at a time, obviously, it has to handle a whole floppy at a time.
  • There’s no ability fix bad data values.
  • There needs to be an automatic mode where educated guesses can be plugged in, and re attempt the checksums. The problem is that the lousy 32-bit XOR checksum used has a potential false positive rate of 1/32. IE, you can’t brute force it because multiple values will work. (See my post on this topic)

I have some fairly unique methods in mind for fixing this data, but some details still need to be worked out.

Please feel free to comment below about the software.