Drive an MCP49XX series DAC with an AVR ATmega

Davide Gironi writes:

Driving that IC is pretty simple, expecially if you have a dedicated SPI hardware interface, like many microchip has.
The ATmega8, used in this example has a dedicated SPI Control Register (SPSR) that one can use to setup the SPI interface.
This library can drive more then one MCP49XX of the same series at the same time, this is done just by selecting the chip using a SS channel for each one.

See the full post on his blog.

Check out the video after the break.

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Internet connected fire/smoke alarm project

Martin Harizanov blogged about his cheap DIY IoT smoke detector:

This project is an upgrade to a previous project of mine – the DIY IoT smoke alarm. It is a more advanced version that uses dedicated hardware rather than the generic “Funky” project + external components. In essence, the module integrates into cheap smoke detectors and provides wireless event transmission plus periodic battery measurements to cloud infrastructure using BBoilRF as a gateway (over MQTT).

More details on Martin’s corner on the web blog. See part 1 here.

Check out the video after the break.

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A look inside a Marconi signal generator

A closer look at a Marconi Instruments signal generator @ jaeblog:

Recently I got a Marconi Instruments 2019 signal generator, capable of generating signals from 80Khz up to 1040Mhz. It can also modulate these signals with AM, FM and more. This instrument is from the mid 80s and is, as far as I can test, still in good operational order.
A signal generator capable of generating over 1Ghz is pretty impressive, especially in the 80s, so let’s have a look inside this unit and see how it’s made.

Nano current meter based on an ATtiny84

Johnson Davies published a new build:

This project describes a simple low-current meter I devised to check the sleep current of different microcontroller circuits, such as ones based on AVR microcontrollers. It’s capable of measuring currents of between 10µA and 30nA with reasonable accuracy, using an ATtiny84 and a few other low-cost parts

Project details at technoblogy.com.

Free PCB coupon via Facebook to 2 random commenters

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:

Some stuff:

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DIY Analog resource monitor for your PC

Sasa Karanovic posted detailed instructions of how to build a physical dashboard for your PC, that is available on GitHub:

The overall architecture is very simple; There is a python script that is running on a PC and collects CPU, memory, network and GPU usage. Then, it sends that information over serial COM port to the hardware monitor board for processing. New voltage values are calculated and passed to the digital-to-analog converter (DAC) which drives analog dials (galvanometers) by applying a voltage that will move the needle to a desired location. Super simple but it get’s the job done.

See the full post at sasakaranovic.com.

Check out the video after the break.

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The Annoying CAPS LOCK warning buzzer

Glen Akins made a USB notification device that make annoying warning noise when CAPS LOCK is enabled:

The only way to make CAPS LOCK even more annoying was to make it audible! Now never type a password in all upper case, join 500 lines together in vi, or turn a harmless forum post into an ANGRY SCREED without warning again! This project uses a PIC16F1459 to monitor the USB output report containing the CAPS LOCK status from the connected PC. When CAPS LOCK is enabled, the PIC turns on an annoying warning buzzer.

Project details at bikerglen.com, see Part 1 here. All design files are available on github.

ATTiny85 Pulse oximeter with photoplethysmogram (PPG) display

tinyPulsePPG, an ATTiny85 Pulse Oximeter with Photoplethysmogram (PPG) display by Jeff Magee:

This project implemented on an ATTiny85 displays a moving Photoplethysmogram together with pulse rate and estimates of SpO2 – blood oxygen percentage. It uses an SSD1306 128×32 OLED display and a Max30102 sensor. It is emphasised that this should not be used for medical purposes. The computation of SpO2 is very approximate and not calibrated in any way. The project is an exercise in software and hardware parsimony.

Project info on GitHub.

Current meter based on ESP-12E and LTC4150

Victor Chew made a simple current meter based on ESP-12E, LTC-4150 and SSD1306 OLED module that measure the average current draw of a variable load accurately:

The meter is powered by the micro-USB port on the ESP-12E. I soldered header pins onto the IN and OUT terminals of the LTC-4150. The whole idea is that one could plug the source battery into the IN terminals, and plug the circuit to be tested into the OUT terminals, press the “Reset” (RST) button on the ESP-12E, and it will start measuring the average current draw of the circuit.

Project info at www.randseq.org. Source code can be found on GitHub.

UPDI Programmer Stick

Johnson Davies designed and built this UPDI Programmer Stick based on an ATmega328P, that is available on GitHub:

This is a USB-stick sized UPDI programmer, for programming Microchip’s new 0-series and 1-series ATtiny chips from the Arduino IDE
It’s based on an ATmega328P, and is essentially an Arduino Uno on a USB stick, so you also could use it as a mini-sized Arduino Uno.

Project details at technoblogy.com.

Free PCB coupon via Facebook to 2 random commenters

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:

Some stuff:

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Open source Bluetooth stack for PIC32/24

Nigan tipped us to a simple open source Bluetooth stack for embedded devices, the SmallTooth:

A newly developed open source Bluetooth stack for PIC32/24
* The code is really easy to understand, very well documented and really small.
* Designed to be extended and ported.
* Works straight out of the box with the PIC32 USB Starter Kit II and should be fairly simple to port to other PIC32 or PIC24 boards.

More details on Guillem’s code.google Project Page, Documentation about the stack. Author’s website www.guillem.co.uk

Via the forum. Thanks Nigan!

Single diode temperature sensor with Arduino ICU (& reverse-bias leakage)

Use a single diode as a temperature sensor with Arduino ICU

Our LED light-sensing experiments lead to an interesting observation: When these loggers are left running overnight they still produce readings because reverse-bias ‘leakage-current’ eventually triggers the Interrupt Capture Unit (ICU) – in the absence of any light. The speed of this self-discharge depends on the ambient temperature. If you deliberately cover an rgb LED with heat shrink, the different color channels have different rates of thermal decay

More details on Underwater Arduino Data Loggers blog.

Bus Pirate cables arrive from DirtyPCBs.com custom cable service

We received 100 Bus Pirate cables using our pinout color scheme from DirtyPCBs.com custom cable service. The cables were just over $1 each for 100 pieces.

The primary reason we ordered these now is to get a feel for how the pinout color scheme works in practice before we commit to it permanently.

The leads are 30cm long, which seems a bit unwieldy in real life. The next version will be a few centimeters shorter.

One end is terminated with 1 pin female “DuPont” connectors. These are easy to use with breakout boards and bread boards that have 2.54mm header pins. We’ll need to choose a nice probe hook and mating crimp eventually.

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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.

Bus Pirate Ultra v1d 2.8 inch display board

In addition to the 2 inch IPS LCD we’re been using with the Bus Pirate prototype “Ultra”, we’re also sending off a PCB for a larger 2.8 inch display. Both panels are 240*320 pixels, so the larger version probably won’t look quite as stunning as the smaller display with high pixel density. If it does pass muster, a capacitive touch screen controller option is available that might be an interesting addition.