I2C Bootloader for ATtiny85 Lets Other Micros Push Firmware Updates

There are a few different ways of getting firmware onto one of AVR’s ATtiny85 microcontrollers, including bootloaders that allow for firmware to be updated without the need to plug the chip into a programmer. However, [casanovg] wasn’t satisfied with those so he sent us a tip letting us know he wrote an I2C bootloader for the ATtiny85 called Timonel. It takes into account a few particulars of the part, such as the fact that it lacks a protected memory area where a bootloader would normally reside, and it doesn’t have a native I2C interface, only the USI (Universal Serial Interface). He’s just released the first functional version for the ATtiny85, but there’s no reason it couldn’t be made to work with the ATtiny45 and ATtiny25 as well.

Timonel is designed for systems where there is a more powerful microcontroller or microprocessor running the show (such as an ESP8266, Arduino, or even a board like a Raspberry Pi.) In designs where the ATtinys are on an I2C bus performing peripheral functions such as running sensors, Timonel allows the firmware for these peripheral MCUs to be updated directly from the I2C bus master. Embedded below is a video demo of [casanovg] sending simple serial commands, showing a successful firmware update of an AVR ATtiny85 over I2C.

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The Almost Useful Machine

[Alex] is no stranger to making machines of negligible utility. A few years ago he made the Almost Useless Machine, a solar-powered system that cuts through a 20mm dowel rod while you wait (and wait, and wait). Enamored by the internet’s bevy of powered hacksaws, he sought to build a sturdier version that’s a little more useful. Approximately five months of free time later, he had the Almost Useful Machine.

It runs on a wiper motor and a recycled power supply from a notebook computer. [Alex] rolled his own board for controlling the motor with an ATtiny25. The circuit turns potentiometer movement into PWM, which controls the motor through a MOSFET. After the cut is finished, an endstop microswitch  immediately cuts the motor.

Every bit of the chassis is aluminum that [Alex] machined by hand. Don’t have that kind of setup? How about a powered hacksaw with a 3D-printed linkage? Make the jump to see it in action, and stick around for the two-part time-lapse build video.

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Tiny Tea Timer for Your Perfect Cuppa

If you’re serious about your tea, you know that the line between a perfect brew and over-steeped dreck is a fine one. Seconds can make a difference, and for the tinkering tea drinker, this might lead you to build a tiny timer with just the features it needs to achieve tea perfection.

The circuit that tea-loving [acidbourbon] came up with for his timer is simplicity itself. It’s just an ATtiny25, an  LED, two pushbutton switches and a piezo buzzer on one side of the PCB, with a coin battery on the flip side. The battery holder is an interesting design – a couple of rows of pin headers and a bit of springy metal. The user interface is as simple as the circuit – the buttons increment the time either one or ten minutes. The timer starts right away, the LED heartbeat counts down the seconds, and a distinctly British tune announces when it’s time for tea.

One possible improvement might be to have the LED flash the number of minutes remaining rather than just a single pulse heartbeat. That would be good feedback that you entered the right time in the first place. Other than that, it’s small enough to be handy, does just one job, and does it well – sounds like good design to us. Of course, if you want to complicate it a bit, you could always automate the tea steeping process.

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ShuttAVR can snap a pic or serve as an intervalometer

shuttAVR-intervalometer-hack

This project started as a simple microcontroller replacement on this IR camera remote control PCB. But the soldering job went rather badly for [Balthamos] so he changed things up and designed his own simple AVR remote shutter release and intervalometer.

The DIP chip seen with most of its legs bent backwards is the ATtiny25 which makes the system work. It’s patched into the traces for the battery connections, button (on the other side of the board) and the IR LED he’s pinching with his left hand. Point it at a Cannon camera and push the button to snap a photo. But as you can see in the clip after the break it also serves as an intervalometer; letting him take several pictures with a user-defined pause between each. That mode is selected by first pressing and holding the button. Once released the chip waits for a second button press to register the delay. The new circuit still fits in the original case after just a bit of alteration to it.

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USB controlled SPÖKA night light

usb-controlled-spoka-nightlight

[wejp] picked up an IKEA SPÖKA night light, but he wasn’t entirely impressed with its functionality. Pressing the top of the ghost’s head causes it to cycle through a few colors, and pressing it a second time locks it into displaying the current color until its tapped again. Inspired by this SPÖKA hack which used a different version of the night light, he tore his down to see what he could do with it.

Upon stripping off the outer cover, he found that the internals were considerably different than those found in its glowing brethren, though they were perfect for what [wejp] had in mind. He removed the rechargeable battery pack as well as the controller board, which sits on a PCB separate from the LEDs. He replaced the stock micro with an ATtiny25, which he uses to give himself a bit more control over the light display.

He couldn’t quite cram all the functionality he desired into the ATtiny, but he planned on powering the light using his computer anyhow, so he installed a small USB port in the back. When connected to his PC, the SPÖKA can be controlled more precisely than when it operates alone.

Unfortunately there’s no video available of the SPÖKA light in action, but there are plenty of images available on his site.

Adding auto-off to a cheap multimeter

[Florin] picked up a cheap multimeter in order to make multiple measurements at one time. Unfortunately, he wasn’t very good at remembering to turn it off when he was finished so he burned through some batteries. Why an auto-off feature wasn’t the first thing coded into the firmware we’ll never know, but [Florin] developed his own hardware-based auto-off circuit.

It sounds like he had all of the components necessary for this on hand already. He grabbed an AVR ATtiny25 in a surface mount package. To keep the board small, he didn’t include an ISP header, but instead made long pads that could have wires soldered to them for flashing the firmware. The microcontroller drives an NPN transistor that can cut off the ground path between the multimeter and its battery. A tactile switch is connected to one of the external interrupt pins and, when pressed, gives you 15 minutes of time to use the meter. After that, the chip kills the power and goes into sleep mode. Simple, and small enough to fit inside the case.

[via Dangerous Prototypes]

Motorcycle current gear indicator

[Vassilis Papanikolaou] just finished building a gear indicator for a motorcycle. This quite a simple implementation compared to some of the other vehicle information displays we’ve taken a look at. You should be able to build and install your own without breaking the bank. An ATtiny25 microcontroller reads data from a couple of hall effect sensors and the neutral switch, then displays the current gear on a 7-segment display.

There’s a magnet on the shifter and two hall effect sensors at the position for ‘gear up’ and ‘gear down’ shifting. The AVR chip keeps track of these and even stores the last position in EEPROM when you shut the bike off. If the device somehow gets off track, it will automatically recalibrate itself next time you shift into neutral, thanks to the bike’s neutral sensor switch.