MIDI to USB adapter with Teensy LC

circuit

Joonas has written up documentation on his MIDI to USB adapter with Teensy LC:

Thankfully, I had a MIDI connector and a high-speed optocoupler at hand, and with these I could implement a MIDI in rather easily. After some investigation with Arduino Uno, it seemed quite simple to receive the serial MIDI bytes and dump them over Arduino serial (I’ll write another post about this later).
However, Arduino cannot become a USB MIDI device very easily, so here comes the really nice part: Teensy LC can, and the Teensyduino add-on included a working USB MIDI and also serial MIDI libraries!

More info at Code and Life site.

Via the contact form.

App note: PointLED® – It’s nice to be different

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New SMD LED design from OSRAM ideal for mounting on PCB holes for illumination. Link here (PDF)

This application note provides insight into the universally deployable and flexibly mountable light source of the PointLED® product family. A fundamental overview of the LED construction as well as the optical and electrical characteristics and performance of the LED are presented.

App note: How to handle a reed switch

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Proper handling of reed switches to prolong operation and or storage, an application note from HSI sensing. Link here (PDF)

Reed switches consist of two or three metal reed contacts (blades) that are hermetically sealed inside a glass tube. This seal, while strong, may be damaged if proper handling is not used. HSI Sensing has years of experience handling reed switches and have identified several best practices.

More ARM1 processor reverse engineering: the priority encoder

full-encoder-labeled

In a previous post, Ken Shirriff reverse engineered the silicon in the ARM1 processor, this time he reverse-engineer the priority encoder in the ARM1 processor:

In this article, I reverse-engineer the priority encoder in the ARM1 processor. By examining the chip layout provided by the Visual ARM1 project, I have determined how this circuit works and created a schematic.
The ARM1 chip is the ancestor of the extremely popular ARM processors used in most smart phones. The ARM1 is a good choice for reverse engineering since it was designed in 1985 and its simple RISC silicon circuits are easier to understand than modern processors. This article jumps into the chip details; if you want an overview of the ARM1 internals, start with my first article on reverse engineering the ARM1.

More details at Ken Shirriff’s blog.

RF probe

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m0xpd writes:

Today I finally got round to building a nice little RF probe kit from Rex, w1rex, the Tuna King over at QRPme.
I took the well-executed PCB which – unusually for Rex – had through hole mounting for the components rather than the ‘Limerick’ construction that recently I’ve come to associate with him…
Following the excellent instructions, I whittled away the PCB at the business end, to make the probe easier to probe and poke into awkward places, then added the four components…

More details at m0xpd’s blog.

Fobble, a general purpose wireless breakout board

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Ken Boak  has been working on a general purpose wireless breakout board – Fobble:

As can be seen from the above picture it contains a number of key features:

  • A resident RFduino  Bluetooth Low Energy Module with ARM Cortex M0 processor
  • 2 layer pcb 50 x 50 mm format- with extended Arduino headers pin-out
  • An X-Bee footprint – with 0.1″ breakout headers – to add your own wireless module
  • Two push button switches – only 1 populated shown
  • Footprint for RGB 0505 LED
  • Detachable power and programmer section
  • Detachable side panels – to make 38 x 32 mm BLE Key Fob
  • 8 pin header to accept 1.3″ OLED display
  • 20mm coin cell or flat Li Po cell power – on rear of Fob pcb
  • Micro – USB connector for recharging Li Po
  • Side Prototyping areas – perforated in 0.1″ matrix
  • 7 pin and 5 pin headers to accept any RFduino accessory shields – for development work

Project info at Sustainable Suburbia blog.

Counting bits in hardware: Reverse engineering the silicon in the ARM1 processor

chip-labeled-bit

Ken Shirriff writes:

How can you count bits in hardware? In this article, I reverse-engineer the circuit used by the ARM1 processor to count the number of set bits in a 16-bit field, showing how individual transistors form multiplexers, which are combined into adders, and finally form the bit counter. The ARM1 is the ancestor of the processor in most cell phones, so you may have a descendent of this circuit in your pocket.

More details at Ken Shirriff’s blog.