Modifying a Tower SG90 servo for continuous rotation with potentiometer position sensing, Part 1: Investigation and continuous rotation

in robotics by DP | 3 comments


Keith wrote an article on modifying a Tower SG90 servo for continuous rotation with potentiometer position sensing:

On its own, the servo takes power, ground, and a position input and moves the shaft within a range of rotation to match the angle requested on its input wire. It has one or more stops in its gearbox to prevent it from rotating past the end of its range; these need to be removed. It also has a potentiometer as part of its positioning system, which — for the usual modification — needs to be tricked into thinking it’s always centered. The modified servo then runs at full speed forward or backward trying to reach a requested position and thinking it has never succeeded in doing so; and the controller requires extra, external rotation sensing if you want to detect what the servo has actually done so far.
I wanted something a little different — PWM H-bridge control of the servo’s motor for variable speed forward and backward and access to the potentiometer to detect position (crudely and at low speed) and count wheel rotations (acceptably and at high speed).

More information on Keith’s blog page.

Posted in robotics | Tagged , , | 3 Comments

8×8 RGB LED array with a Raspberry Pi

in LEDs, R-Pi by DP | 0 comments


Bob Davis has been working on an 8×8 RGB LED array with a Raspberry Pi project:

I have been working on a book of Raspberry Pi projects. One of the projects is an 8×8 three color LED array. I picked up some more of them on eBay lately and they had a different pin-out.
The MEU 8860 RGB pin-out as seen from above. I use Dx for the rows as Rx is used for Red.

Check out the video after the break. Continue reading →

Posted in LEDs, R-Pi | Tagged , | Leave a comment

SimpleLink ultra-low power wireless MCU platform

in wireless by DP | 0 comments


Allie informs us of TI’s new SimpleLink ultra-low power wireless platform for Bluetooth Smart, 6LoWPAN, ZigBee, Sub-1 GHz and ZigBee RF4CE

Today, TI is helping manufacturers throw out the battery for their IoT devices with its new SimpleLink ultra-low power wireless MCU platform. This new wireless MCU family brings a first to the industry, a single-chip that supports multiple wireless connectivity standards with identical RF design – Bluetooth Smart, ZigBee, 6LoWPAN, Sub-1 GHz, ZigBee RF4CE and proprietary modes up to 5Mbps.
The new easy to use SimpleLink ULP platform is the lowest powered MCU in the industry with an integrated ARM Cortex-M3 MCU, radio, Flash/RAM, analog-to-digital converter, peripherals, sensor controller and built-in robust security on chip.

Via the contact form.

For more information visit


Programming Arduino Pro Mini with Bus Pirate

in Arduino, Bus Pirate by DP | 1 comment


Dana Harding writes:

Program an Arduino Pro Mini 328 [sparkfun] board using a Bus Pirate.
I tried setting up the Bus Pirate as a transparent bridge for UART to use the Arduino boot loader. I got as far as manually sending 0x30 0x20, and receiving a 0x10 0x14 – establishing communication over UART… But couldn’t get the Arduino IDE to actually upload a program to it.
It turns out – version depending – that avrdude can use the buspirate as an SPI programmer.

Get an assembled Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

Arduino Uno R3 graphics accelerator shield uses no pins

in Arduino by DP | 12 comments


Andy Brown has written an article detailing his Arduino graphics accelerator open source project:

This project brings together the knowledge that I’ve gained over the last few years to bring you a graphics accelerator for the Arduino Uno R3 based on an ARM Cortex M0 core attached to a 640×360 LCD from the Sony U5 Vivaz cellphone.

Via the contact form.

Check out the video after the break.

Continue reading →

Posted in Arduino | Tagged , , | 12 Comments

DirtyPCBs: HDC1000 temperature and humidity sensor breakout, with Arduino library

in Arduino, by DP | 0 comments


Francesco Truzzi published a new build: a breakout board for the TI HDC1000, a tiny (8BGA) temperature and humidity sensor

The boards were again fulfilled by DirtyPCBs, perfect for this kind of small projects.
So here are the pictures of my board and here are the features:

  • Address selection jumpers: ADR0 and ADR1 are tied to GND by default but you can jump them to VCC in order to change the address of your sensor (default:0x40)
  • I2C pull-ups to VCC for SDA, SCL and DRDYn. If you don’t want to use the latter, just don’t solder the resistor and leave it floating
  • 3-5V input, logic 5V tolerant (3.3V recommended)

Via the contact form.

#FreePCB via Twitter to 2 random RTs

in Free PCBs by DP | 0 comments

KHOS-2-3-4-5-6P 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.

Posted in Free PCBs | Tagged | Comments Off

1mm pitch flex cable passthrough

in dev boards, LCD by DP | 1 comment


Kuzyatech has a new project posted, a Flex (FPC) 1mm cable passthrough breakout:

By popular demand, the breakout/passthrough combination boards family now includes a 1mm pitch variant
This version handles up to 30 signals which seems to be a practical limit of most 1mm FPC connectors. Each signal is numbered and brought to a 0.1mm spacing header for easy connection to your favorite logger/analyzer/scope.

For more information visit the Kuzyatech’s site. It’s also up on Tindie.

Posted in dev boards, LCD | Tagged , , | 1 Comment

Clocked 8-bit random pattern generator for CMOS synth

in hacks by DP | 0 comments


Michael of Acidbourbon built a clocked 8-bit random pattern generator and wrote a post on his blog detailing its assembly:

The idea behind this circuit is really simple:

  1. Build a white noise source
  2. Amplify the noise until it has CMOS/TTL logic level (0V=Lo, 5V=Hi)
  3. Use a clocked flip flop to sample the high frequency noise at a fixed rate (with a low frequency clock signal).

And then you should get a random sequence which changes at a fixed rate. If we use a shift register (a chain of flip flops), we can produce a multitude of binary random signals, which all toggle to the same rhythm.

Check out the video after the break. Continue reading →

STM32CubeMX GCC Makefile project

in software by DP | 3 comments


Baoshi writes:

Writing peripheral initialization code is probably the most tedious work in embedded development. It always successfully stops me from starting a new project. I believe engineers at STMicroelectronics share the same pain. Therefore they created STM32Cube firmware and STM32CubeMX graphical configuration tool, which turns numerous key strokes and page flips into just a few mouse clicks. STM32CubeMX is free software, but the initialization code it generates require compiler tools carrying hefty price tags, IARARM, Keil ARM-MDK, and Atollic TrueSTUDIO, to name the few. Fair enough these compilers do offer free editions with limited functionality. But I still prefer unrestricted, free tool that is easily scale-able for my current and future projects. Just like the GNU Make and ARM GCC toolchain I described in Opensource STM32 development.

Posted in software | Tagged , , | 3 Comments

App note: The effect of pan material in an induction cooker

in app notes by DP | 1 comment


A good read on induction cooker and the effects of pan material used, app note(PDF) from ON Semiconductors.

Induction heating is a well established method of generating heat in metal goods and has been used for decades. The induction cooking market is well established, but little has been written regarding the properties and interactions of the induction coil when a pan is placed on it. It can be seen that any metal pan will have losses due to eddy currents; however, those losses are small compared to those in pans with magnetic properties.

The type of magnetic material does not have an appreciable impact on the losses; however, the losses increase with frequency for all pans. Pushing switching frequencies higher will reduce the cost of the coil, resonant capacitor, and increase the efficiency of the unit. As switching devices advance in switching speeds, frequencies for these types of cookers with also increase to take advantage of these improvements.

Free PCB Sunday: Pick your PCB

in Free PCBs by DP | 77 comments


We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

Continue reading →

Posted in Free PCBs | Tagged | 77 Comments

App note: Using the DAC as a function generator

in app notes by DP | 0 comments


A function generator from an C8051 DAC application note(PDF) from Silicon Labs

This document describes how to implement an interrupt driven multifunction generator on C8051 devices using the on-chip digital-to-analog converter (DAC).

Four different waveforms expandable to any periodic function defined in a table.
– Sine Wave (Table Defined)
– Square Wave (Calculated)
– Triangle Wave (Calculated)
– Saw Tooth Wave (Calculated)
* Allows selection of the frequency and amplitude of waveform at run time.
* An interactive interface with a PC using the serial communications port and HyperTerminal or an equivalent program.

App note: Adding an ADC to the Raspberry Pi

in app notes by DP | 3 comments



Adding an ADC to the Raspberry Pi app note (PDF!) from  FTDIChip:

This application note will show how to connect the RPI-Hub-Module to the Raspberry Pi and install FTDI drivers to control the module. The application note will then explain how the module may be used to read values from an external ADC device over the SPI interface.

Posted in app notes | Tagged , , | 3 Comments

App note: USB HID bootloader for PSoC 3 and PSoC 5LP

in app notes by DP | 0 comments


An application note on USB HID bootloader for PSoC 3 and PSoC 5LP from Cypress:

AN73503 describes how to implement a USB bootloader for PSoC 3 and PSoC 5LP devices by using the USB Human Interface Device (HID) class. It also shows how to build a Windows-based USB host program. A PSoC Creator project and an example host program are included.

DirtyPCBs: C64FC 16K edition ready

in AVR, by DP | 0 comments


Stian Søreng writes:

A stack of release candidate 3 boards of the C64FC are on my desk, and a few changes have been made since RC2. We’re talking 16K support, software switches to select 8K/16K cartridge, cart disable support, bugs fixed and patched.
I also want to give a good shoutout to DirtyPCBs for their excellent service on this run. 9 days (!) after the order was submitted, a set of high-quality boards were on my desk. This is by far the fastest and cheapest service I have ever used.

Free PCB coupon via Facebook to 2 random commenters

in Free PCBs by DP | 2 comments


Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters.  The coupon code usually go to Facebook ‘Other’ Messages Folder .  More PCBs via Twitter on Tuesday and the blog every Sunday.

Don’t forget there’s free PCBs three times every week:

Continue reading →

Posted in Free PCBs | Tagged | 2 Comments