App note: Using the Master SPI Mode of the USART module

application note

Atmel’s application note (PDF!) Using the Master SPI Mode of the USART module:

• Enables Two SPI buses in one device
• Hardware buffered SPI communication
• Polled communication example
• Interrupt-controlled communication example

For the majority of applications, one Serial Peripheral Interface (SPI) module is enough. However, some applications might need more than one SPI module. This can be achieved using the Master SPI Mode of the devices with this feature such as Atmega48.

App note: Software phase locked loop design using C2000 Microcontrollers for single phase grid connected inverter



This application note (PDF!) from TI details the design of Single Phase PLL:

Grid connected applications require an accurate estimate of the grid angle to feed power synchronously tothe grid. This is achieved using a software phase locked loop (PLL). This application report discusses different challenges in the design of software phase locked loops and presents a methodology to design phase locked loops using C2000 controllers for single phase grid connection applications.

Things to avoid when sending PCBs to the fab house


Sjaak shared some tips when sending PCBs to the fab house:

I usually collect a few PCB designs before sending them off to the PCB fabhouse. I prefer to use as I know Ian from for a long time and think he provides good quality, and fast turn around time for your money. Also tend to be loyal to my suppliers so a better alternative may exist. The main reason I wait before sending them off is that I want my PCBs returned quickly. DirtyPCBs provide fast DHL shipping (about 2-3 days to .nl) but it is quite expensive (about 30 USD) compared to the manufacturing the PCBs. Luckily the PCBs don’t weight a ton, and adding more designs will not add much additional shipping costs.

More details at site.

Music Thing Modular Axoloti control board


Tom Whitwell from Music Thing Modular built a DIY control board for Axoloti, that is available on Github:

Axoloti is a very nice €65 audio board from Belgium, the closest thing I’ve yet seen to an Audio Arduino; lots of easy analog ins and outs for pots and switches, enough power to do interesting audio, and a nice visual patching system. A bit like a Nord Modular for 2016.
I’ve put together a simple control surface for my Axoloti; pots, buttons, LEDs and a joystick.

Project info at Music Thing Modular site.

Check out the video after the break.

Instruments for the GSXR


Josh from imsolidstate made a new dash panel for his streetfighter based on an ATmega128, a Planar EL 160×80 display, and an Epson S1D13700 controller:

Since the GSXR is now a street fighter the factory gauges won’t do, and I wanted something I could log air/fuel ratios with so I can jet the bike. I went a little overboard making a new dash.
I had a Planar 160×80 EL graphic display that’s been in my parts bin for years that I’ve always wanted to use, and this was perfect. Unfortunately it doesn’t have a controller so I had to interface it to the CPU with an Epson S1D13700 graphic controller. The display indicates speed from a GPS module, air/fuel ratios from the wideband O2 sensor, engine temp, battery voltage, time from GPS, and RPM. I used a light sensor to sense ambient brightness levels and dim the display by changing TC/R in the graphics controller. The refresh of the display is high enough to allow a large dimming range without flickering. The EL display can be refreshed at up to 240Hz.

Project info at

Check out the video after the break.

ESP8266 breadboard adapter board


Markus designed a single-sided ESP-12/ ESP-07 breadboard adapter PCB:

Features are:
– Fits ESP-12 and ESP-07 module
– Single-sided self-etchable design
– Few, cheap parts in SMD
– Breadboard-style – one row on each side accessible
– Vin >4.5V (max. 7V) input possible with 3V3 onboard voltage regulator (with two capacitors 10µF)
– Power-indicator LED
– (Schottky-) Diode as reverse polarity input protection possible (solder 0 Ohm resistor or just connect the two pads for no protection)
-RST, CH_PD, GPIO0 with 4k7 pull-up resistors on board (resistors can be omitted if remote access of those GPIOs is needed)
– GPIO15 with 4k7 pull-down (see above)
– Tactile switch connected to GPIO0 to get into flash mode
– Single post for 3.3V output near voltage regulator

Project info at Wireless Sensor Networks blog.

Mullard 3-3 Amplifier project (part 2)


Dilshan Jayakody writes:

This is a second article related to Mullard 3-3 Amplifier Project and in this article we introduce HT transformer and HT power supply related to this amplifier. As mentioned in previous post, power supply unit of this tube amplifier is constructed using 400V 5A bridge rectifier, 220µF (400V) and 82µF (400V) electrolytic capacitors.
The most vital component of this power supply is HT transformer and due to limited availability we construct this transformer by ourselves.

More details at Dilshan Jayakody’s blog.

555 timer teardown: Inside the world’s most popular IC


Another great teardown article by Ken Shirriff, a look inside the 555 timer chip:

Given the popularity of the 555 timer, I thought it would be interesting to find out what’s inside the 555 timer and how it works. While the 555 timer is usually sold as a black plastic IC, it is also available in a metal can, which can be cut open with a hacksaw revealing the tiny die inside.

More details at Ken Shirriff’s blog.

App note: Voltage generating circuits for LCD contrast control


Another application note from Hantronix, Inc. on simple to digitally controlled efficient power supply for LCD display contrast. Link here (PDF)

Many LCD display modules require a negative or positive voltage that is higher than the logic voltage used to power an LCD. This voltage, called Vl, Vee or the bias voltage, would require a second power supply in the application device. If this power source is not available the LCD bias voltage must be generated from an existing voltage, either the logic voltage (+3.0-+5v) or a battery. This application note describes circuits for generating either a negative or positive LCD bias voltage from such a voltage source.

The LCD bias voltage is used to power the circuits that drive the LCD glass. This voltage sets the contrast level of the LCD. Since any changes in this voltage will cause a visible change in the contrast of the LCD it must be regulated to better than about 200mV. Any noise or ripple on this signal may cause visible artifacts on the LCD so they must be kept below about 100mV.