Trochotron Industries

The $7 microcontroller development kit

joshua — Thu, 03 Dec 2009 07:36:32 +0000

Seven dollars might buy you a burger at an upscale burger joint, or you can get a complete microcontroller development kit from STMicroelectronics. Most likely now holding the throne of lowest cost complete development kit (previous holder was TI’s $10 EZ430 USB stick?), the $7 STM8S-Discovery includes a detachable programmer, target board, and prototyping board. The target board hosts an 8-bit STM8S105C6T6 microcontroller running at 16Mhz, with 32K of flash, 2k of RAM, and 1K of EEPROM. This puts it in similar territory as the AVR 8-bit microcontrollers used in the Arduino boards. At this price onboard devices are scarce, but nice touches include a selectable 5v/3.3v jumper, a capacitive touch sensor, an onboard LED, and a prototyping area with through-hole and an SO-16 SMT footprint. And it has nice rubber feet to boot.

Here’s the pic goodness, note the fancy retail-ish packaging:

Teensy 2.0 now available

joshua — Wed, 07 Oct 2009 05:21:34 +0000

The Teensy USB development board from PJRC has been upgraded to a new board featuring Atmel’s newer ATmega32U4 device. With this comes the benefits of the new device, including A/D channels, extra I/O (including PWM and I2C) and more memory. By default it operates at 5v, but it can be converted to operate at 3v3, a very nice feature for interfacing with modern peripherals. Even with the additional pins and functionality, it’s just as small as the original Teensy. Great work, Paul!

And the best part… the new Teensy board is even cheaper than the old one. Now the price has been dropped to just $18 (or $21 with pins.) I’m certainly planning on ordering one.

Also of note, the Teensy 2.0 is now available for order from Adafruit Industries. This should boost product awareness and get this great board into the hands of more developers.

Repurposing 2: Li-poly power supply for microcontrollers

joshua — Sun, 23 Aug 2009 01:58:24 +0000

The repurposable device featured here is a Digipower Solutions Jumpstart JS1-V3 emergency cell phone charger, which charges and provides power via a pair of male and female mini-A USB connectors. The device is intended to provide additional capacity for phones equipped with a suitable connector. The packaging claims that it will provide an hour of talk time for most cell phones, but did not list a mAh rating. (What’s the standard for converting from mAh to hour of talk time?) There may be other devices like it on the market; this one is particularly tiny and features a clear plastic case and an interesting bonus feature, a white LED which works as a flashlight when a button is pushed. Internally visible are the lithium polymer battery and charging circuitry.

While I’m not really interested in using it for my cell phone, it seems particularly ideal for powering small projects. In particular, it has the right connector for plugging into the various tiny USB microcontrollers I’ve been working with. I’ve been using a larger lithium-ion battery with USB output, and even the wonderful MintyBoost Altoids-tin charger, but they’re much, much larger than the microcontroller boards themselves. The JS1-V3 is perfectly sized for this application.

Whenever I get some new gadget, for some reason my first instinct is to open it up and try to figure out what’s in it and how it works. One of the things I love about the internet is that you can find very nice pictures of the innards of most gadgets, saving the trouble (and risk) of opening the device just to see what’s inside. Here are some pictures of the Jumpstart and its innards, for those similarly interested. In one, I’ve removed the insulating tape from the LiPo battery to show the battery specs, which reveal that that the battery is a 220 mAh 3.7v 20×25x6.2mm Li-poly cell, manufactured by B&K battery. The last photo shows the Jumpstart battery plugged into an AVRopendous2-DIP board, providing portable power for the board.

SparkFun AVR Stick

joshua — Mon, 13 Jul 2009 07:42:43 +0000

Here are some photos of the SparkFun AVR Stick, which at $9.95 provides a very inexpensive USB solution, based on the ATtiny85. This board is using a software stack to emulate a USB 1.1 device interface, in particular the V-USB stack (formerly known as AVR-USB) from Objective Development under GPLv2 or under a commercial license. I’ve seen the V-USB stack used by a couple projects recently, seems to be gaining some mindshare among the DIY crowd.

As you can see the board I have is tiny, yet still manages to provide headers for all 8 of the ATtiny85s pins in addition to a 6-pin AVR ISP connector. On the board I have, there is some spotty-looking structural solder on the USB connector contacts, but the board otherwise looks clean and seems to work fine. The board comes pre-programmed with a data-logging application that reports readings on two ADC channels to the host as a USB HID report. And as SparkFun happily points out, “This thing is meant to be hacked!” Full source code is available under an open license, which builds cleanly and looks to be reasonably easy to repurpose.

Atari Punk Console synth for SparkFun simon

joshua — Sat, 13 Jun 2009 08:05:01 +0000

Inspired by the square wave style output of the SparkFun game, I’ve created a version of the Atari Punk Console synthesizer. This version uses the digital buttons on the Sparkfun simon board instead of potentiometers. The left two buttons control the period/frequency and the right two buttons control the pulse length.

Features:

- 50Hz to 20kHz frequency range

- button LEDs turn off to indicate end of range

Download:

simon-atari-punk-console-v1.zip – minimalistic drum machine for the SparkFun simon game platform (released under Creative Commons v3.0 attribution share-alike license.)

SparkFun simon drum machine v.1

joshua — Fri, 12 Jun 2009 07:41:45 +0000

Here’s a new app for the SparkFun simon game platform, simon drum machine. This is a very minimalistic drum machine, based loosely on the original SparkFun example code. It works by sequencing through each light at approx. 120 beats per minute. At powerup the lights are sequencing, but each beat plays no notes. Pressing the corresponding button cycles through a set of fixed count, length and type beats played for that button. It’s a fun example and the code may be a good start for someone wanting to experiment more with the various sounds possible on this platform. (The platform drives a speaker directly with the ATmega168 pins, providing for a roughly square wave output.)

Features:

- 11 built-in selections for each drum

Download:

simon-drum-v1.zip – minimalistic drum machine for the SparkFun simon game platform (released under Creative Commons v3.0 attribution share-alike license.)

SparkFun Simon example redux

joshua — Wed, 10 Jun 2009 08:26:42 +0000

Here’s my updated version of the SparkFun Simon v21 source code. Main improvements are:

- Code: code cleanups, more functions and comments

- Build: easily selectable between board revisions (6-25-08 and 4-9-2009 supported, but only the 6-25-08 has been tested.)

- Usability: buttons held down too long are no longer registered as two button presses.

- Code: Simplified psuedo-random number generator

Downloads:

simon-v21-r1.zip – Updated example source code for SparkFun Simon game (released under Creative Commons v3.0 attribution share-alike.)

SparkFun Simon surface mount soldering kit

joshua — Mon, 08 Jun 2009 06:01:48 +0000

At this year’s Bay Area Maker Faire, the SparkFun booth was host to soldering classes, where aspiring Makers could learn soldering by assembling kits for functional devices. SparkFun donated the kits and asked for a small donation that went to local charities. The SparkFun blog mentions that they raised $4970, way to go SparkFun! There were classes on both through-hole and surface-mount soldering, each featuring a SparkFun soldering kit. The project for the surface-mount class was the SparkFun Simon kit, which consists primarily of surface-mount components, including an Atmel ATmega168, and also features SparkFun’s slick LED-lit, monome-inspired button pads. I was lucky enough to be able to attend the surface-mount class. Even though I’m very inexperienced at SMT soldering, I successfully assembled the kit during the class. (Thanks to the expertise and moral support of the SparkFun team!) This is a great kit and a wonderful confidence booster for anyone considering creating their own surface-mount project. If you’re curious, you can see my handiwork in the pictures below. I’ve bought commercial products from China that looked worse, so I’m fairly happy with the results.

After the class I mounted programming headers and was able to load a modified version of the SparkFun example code on it. (N.B., there are multiple versions of the board. If you have the older 6-25-08 revision, try the files listed here which more closesly match that board.) I spent some time cleaning up the example code and making minor improvements; I’ll post a link shortly.

Having quickly become bored with the Simon game, I’ve been exploring what other possibilities the board may have. Still working on them; I’ll post details and source code when I get a chance.

AVRopendous2-DIP pix

joshua — Tue, 02 Jun 2009 08:24:50 +0000

Received the AVRopendous2-DIP from Opendous, Inc. today, and as promised, here are some pictures of the board. For now I’ve just plugged it in and tested the pre-programmed Keyboard Test demo, which displays the pin name when you ground a pin. It’s always nice to have a way to verify a development board is working out of the box, before moving on to programming and new development.

This board is the ‘nh’ version, without headers. (Nice bonus, since I like to solder pins on the top side and use jumper wires to connect other boards.)

In the pictures you can see the handy 5v/3v3 selector jumper. Note also the 1.27mm pitch JTAG connector in the center, which seems to me like a bit of an afterthought. The other side of the through-holes are hidden behind the ATmega32U4, so it seems like it would be a challenge to solder on any sort of connector. Fortunately, as the included instruction sheet points out, all of the JTAG pins are accessible on the outside 2.54mm pins as well.

One other difference from the Teensy board is the additional HWB button to trigger the bootloader. This means it’s possible to reset the ATmega32U4 without triggering bootloader mode, also I believe the HWB button can be used as an input after the bootloader has handed off control to the main program.

New AVRopendous models

joshua — Thu, 28 May 2009 08:11:37 +0000

One product very similar to the Teensy USB development board are the open-source (hardware and software) avropendous boards, which now seem to be available in a DIP form factor ala the Teensy board, at a similarly low price. The AVRopendous-DIP ($22) uses the same AT90USB162 as the Teensy board, and allows selecting 5v or 3v3 operation via a jumper. There seem to be some more recent additions to the AVRopendous-DIP family, in particular the ATmega32U4-based AVRopendous2-DIP ($29), the AT90USB646-based AVRopendous3D-DIP ($32), and the AT90USB647-based AVRopendous3H-DIP (not yet for sale?) The 3D and 3H variants provide a more powerful microcontroller, and the 3H variant adds the ability to function in USB host or OTG modes. Not to be dismissed however, the AVRopendous2-DIP has more than double the memory (both flash and RAM) of the AT90USB162-based products and can supply the most current (450ma) at 3.3v.

Most of the things I’m interested in interfacing these days is 3v3, which tend to require extra components to safely interface to a 5v device like the Teensy board. I looked into what it would take to modify the Teensy operate at 3v3, it should just barely be doable with some very delicate soldering. (I had hoped there was some bit of the Teensy design that would make this trivial, like a 0-ohm resistor I could move to make it work at 3.3v. Alas, no such luck…) The AVRopendous design does make this trivial, with it’s jumper-selectable voltage. It’s not a perfect substitution since the AVRopendous lacks the compact bootloader that the Teensy ships with (although made up for by additional flash memory on the AVRopendous2-DIP), and the device has a slower clock (8mhz) that is required to work at both voltages. However, the $25 ATmega32U4-based AVRopendous2-DIPnh (with no headers) option is a deal I couldn’t pass up… Expect to see some pix and a review here when it arrives.