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Paul Bleisch

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Make a Custom Membrane Keypad for Arduino

My son got one of these Leap Frog toys a few years ago as a gift.  He enjoys playing with it very much.  I am not sure how much counting and learning he is doing but it makes funny noises and sings to him so its a lot of fun.

Recently the unthinkable happened.  It died.  Not the batteries but something else.  I took the back off to look at what might be wrong (which was very easy for a toy).  Unfortunately, other than the speaker, a switch, battery compartment, and a ribbon cable to the front, there wasn’t much to investigate.  A couple of glop tops and nothing else.  I fiddled a bit more with it but everything “external” seemed fine.

Did I mention my son really loves this toy?

Continue reading “Make a Custom Membrane Keypad for Arduino”

From Breadboard to Protoboard

The time has come to clear some space on my breadboard so I can continue to build out the remainder of the system. I’ve collected a few prototype boards from Futurlec by tossing a few in each order over a few months. I bought a few different flavors of boards (PROTO777, PRBRDLG, and EXPBRD) to see which worked best for my random projects.

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Debugging stuck bits

I’ve been blocked on making progress on the retro pc project due to bad reads from the ROM. The seemingly simple snippet of boot code should light an led wired to to the i/o ports (any port).

section .text
resb 0x7F0
org 0x7F0

start:
mov al, 0x1

 

again:
out 0x10, al
jmp again

When assembled, this turns into the following x86 bits:

00007f0: b0 01 e6 10 eb fc

Unfortunately, when I tried to boot the bundle of wires on the breadboard, I got the following while looking at AD[0:7] on the 8088.

00007f0: b0 01 e2 10 ...

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Using Ultrascope for Rigol DS1052E

I’ve become more and more annoyed at having to export images from my Rigol scope to a flash drive plugged into the device. I’d much prefer to capture signals and images directly from my Macbook. Unfortunately, the PC software that comes with the Rigol — Ultrascope — does not run on Mac OS X. Boo. Over the last couple nights, I’ve played with the idea of writing a Cocoa app to pull data from the scope. USBTMC + Cocoa seems like a pretty good path to go.

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Sometimes it is a bad part… sometimes.

I’ve spent the last few weeks working on my retro pc project. The first step with the 8284 seemed to go well but the trouble began when I tried wiring up the 8088. I wasn’t getting anything remotely close to the expected boot sequence. According to the datasheet and
The 8088 Project Book
a few clocks after dropping RESET back to zero, the 8088 should raise ALE after placing 0xFFFF0 on the address lines.

No such luck.

Continue reading “Sometimes it is a bad part… sometimes.”

Starting a Retro PC using The 8088 Project Book

Several months ago, I purchased a copy of Robert Grossblatt’s classic The 8088 Project Book in hopes of building a retro 8088 computer. My plan was to scavenge the parts from craigslist, ebay, and a couple Seattle area used computer junk stores. My adventures locally didn’t result in many parts though I did have much fun finding all those old ISA cards. I did manage to buy quite a few intel parts (8259s, 8255s, etc…) and a bunch of 74xx TTL parts from a gentleman in the area who was clearing out old stuff. But I still didn’t have an 8088 and a couple other necessary support parts. My queries to craigslist resulted in offers to sell me old 8088 PCs for crazy prices. Eventually, I gave up on finding the parts locally and started adding the remaining pieces to various digikey and futurlec purchases. This past weekend the final piece – the 8284 – arrived which is good because it is pretty important being that it drives the clock for the entire system.

Continue reading “Starting a Retro PC using The 8088 Project Book”

An amateur’s look at the Rigol DS1052E

My Rigol scope showed up a couple weeks ago and I have had some time to play with it. I’m no expert on test equipment but I’ve been very happy with the DS1052E so far. In particular there have been several nice surprises along the way.

Continue reading “An amateur’s look at the Rigol DS1052E”

Rigol DS1052e

About a year ago I had to make a tough budgeting decision – something that many fellow hobbyists have to do.  Which would it be – an oscilloscope or a logic analyzer? At the time I was doing alot of FPGA and planning to do microcontroller stuff so I bought a LogicPort from Intronix.  While a great purchase, I’ve found myself looking at analog signals or higher voltages than I expected.

I began watching Craigslist for used oscilloscopes, hoping to pick up a cheap 25Mhz scope.  Meanwhile, I came across David Jones’ eevblog and his review of the Rigol 1052e. In some sort of sign, the Rigol DS1052e’s went on sale this past week for $399 (interestingly only $10 more than I paid for my LogicPort).  Now, I did find a few 50Mhz 2-channel scopes (HP, Tektronix, Hitachi) locally for between $250 and $350 but for a little more I get a new DSO.  Yum.

I haven’t received the scope yet.  I’ll post some info when I get it.  I should also do a review of the Intronix LogicPort – a nice piece of kit.

What’s more is that in the process I discovered eevblog which is outstanding.  I must have spent three hours watching past episodes the other night until 2:00 in the morning.  Great stuff.

Futurlec’s value packs

I’ve decided to invest in some component “staples” so I can more easily do simple projects with the kids.  After looking around a bit, I decided to get a few  value packs from Futurelec.  Specifically, the 1/4W resistor pack, a ceramic cap pack, mylar cap pack, a diode pack, and the linear ic pack.  They shipped quickly and the pre-sorted and labeled nature made it easy to pop into my cheapo Home Depot containers.  Great stuff.

I left the resistors in their shipping package since they were labelled for me.
I left the resistors in their shipping package since they were labelled for me.

I came upon Futurlec while looking for 8088 related parts for another project. If you haven’t tried them they seem to have great prices for 74LSxx stuff and the like (compared to digikey and jameco) and ship small orders.

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