Extracting ROM constants from the 8087 math coprocessor’s die

Ken posted an article taking a closer look at Intel 8087 chip:

Intel introduced the 8087 chip in 1980 to improve floating-point performance on the 8086 and 8088 processors, and it was used with the original IBM PC. Since early microprocessors operated only on integers, arithmetic with floating-point numbers was slow and transcendental operations such as arctangent or logarithms were even worse. Adding the 8087 co-processor chip to a system made floating-point operations up to 100 times faster.
I opened up an 8087 chip and took photos with a microscope. The photo below shows the chip’s tiny silicon die. Around the edges of the chip, tiny bond wires connect the chip to the 40 external pins.

More details on Ken Shirriff’s blog.

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Arduino to Nokia 84×48 LCD Heartbeat Display

Bob writes:

I am working on some Arduino biometric designs perhaps for a new book. So far I have created the two line 1602 LCD display and now the Nokia 84×48 display. The Nokia display is more fun to work with since I can do a oscilloscope like display across the screen. I am working on writing code that works with both an Arduino UNO and with the ESP8266 or the “D1” board.
You can connect a NOKIA display easily using a header extender. You only need to connect five pins this way. The other two are power and ground and they use jumpers to 3.3 Volts and ground.

More details on My Commentary and Technical help blog.

Check out the video after the break.

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3d printed portable arcade controller

Facelesstech has published a new build:

So I recycled the Arduino pro micro off of one of my old controllers, In doing so I messed the pin 16 up so I had to use one of the analog pins instead. The wiring was quite simple really. I ran a ground wire round all the buttons, burning off the silicon where needed. Next I wired up the 5v and GND for the 6 button because they light up, Again I just ran a 5v loop around them and then tapped off the GND wire using some sold core wire to make it look neat.

See project details on Facelesstech blog. Project files are available on GitHub.

Check out the video after the break.

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Building an ATmega 1284p based data logger

A detailed instructions of how to build an ATmega 1284p based data logger:

In this tutorial, a logger is built using a 3.3v Moteino MEGA with a 1284p CPU @ 16Mhz, w 4K eeprom,16K SRAM for variables & 128K program space. Considerably more than the 328’s 1K eeprom, 2K ram & 32K progmem. Also has a spare serial port for GPS/NEMA sensors.

See the full post on Underwater Arduino Data Loggers blog.

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Tandy 1000 upgrades / PS2-Tandy keyboard adapter

Vintage computer Tandy 1000 upgrade @ smbaker.com:

A Tandy 1000 was the second computer that I owned, the first was a Tandy CoCo. Note that I keep a slightly different mental “computers that I owned” list and “computers that I used list”. There are a few computer I was able to gain access to and play with perhaps before the Tandy — computers like the Convergent NGEN, and the IBM 5150.
Owning computers is fun, but modifying computers is even funner, so I set about to modify the Tandy 1000. A few modifications were necessary — for example I didn’t yet own a Tandy keyboard, so I had to make myself an adapter to use a PS2 keyboard on the Tandy 1000.

More details on Dr. Scott M. Baker blog.

Check out the video after the break.

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App note: Probing oscillator output

This application note from SiTime gives practical guidelines for the effective probing of oscillator output, shows common mistakes and explains how to identify and avoid potential probing issues. Link here (PDF)

Electrical engineers often use oscilloscopes for purposes ranging from checking simple, lowspeed digital signals to accurate waveform and jitter measurements. They need to use probes to directly access arbitrary signals on a PCB. Probes can, however, put extra load on a signal or distort the waveform displayed on a scope. Therefore, probing should be done carefully.

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App note: Definitions of VCXO specifications

App note from SiTime about Voltage controled crystal oscillator (VCXO) specification, Link here (PDF)

VCXO are frequency control devices that allow change of output frequency as their input voltage varies. In selecting a VCXO for any application, a number of device performance specifications must be considered. This application note attempts to clarify the key VCXOspecific performance specifications, and to illustrate some of the tradeoffs associated with using a VCXO in an application.

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Tiny transformer inside: Decapping an isolated power transfer chip

Ken Shirriff writes:

I saw an ad for a tiny chip1 that provides 5 volts2 of isolated power: You feed 5 volts in one side, and get 5 volts out the other side. What makes this remarkable is that the two sides can have up to 5000 volts between them. This chip contains a DC-DC converter and a tiny isolation transformer so there’s no direct electrical connection from one side to the other. I was amazed that they could fit all this into a package smaller than your fingernail, so I decided to take a look inside.

See the full details at righto.com.

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#FreePCB via Twitter to 2 random RTs

Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

 

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