Microcontrollers

2276 Articles

A Cheap DIY PLC Based On The Atmega328P

August 22, 2024 by 42 Comments

If you’re running a big factory, you’ve probably got a massively expensive contract with a major programmable logic controller (PLC) manufacturer. One shudders to think about the cost of the service subscription on that one. If you’re working on a smaller scale, though, you might consider a DIY PLC like this one from [Mr Innovative.]

PLCs are rarely cutting-edge; instead, they’re about reliability and compliance with common industry standards. To that end, this design features the ATmega328P. Few other microcontrollers are as well understood or trusted as that one. The device is compatible with RS232 and RS485 and will run off 24 VDC, both of which you would find in a typical industrial environment. It offers 24 V digital inputs and outputs, as well as analog inputs and outputs from 0 to 10 V. [Mr Innovative] demonstrates it by hooking up a DWIN human-machine interface (HMI) for, well… human interaction, and a variable frequency drive to run a motor.

If you want to run a basic industrial-lite system but can’t afford the real industrial price tag, you might enjoy tinkering around at this level first. It could be a great way to get a simple project up and running without breaking the bank. Video after the break.

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Roll Your Own Presence Sensor

August 16, 2024 by 7 Comments

[Mellow_Labs] wanted an Everything Presence Lite but found it was always out of stock. Therefore, he decided to create his own. The kit uses a millimeter wave sensor as a super-sensitive motion tracker for up to three people. It can even read your heart rate remotely. You can see a video of the project below.

There are a few differences from the original kit. Both use the C4001 24 GHz human presence detection sensor. However, the homebrew version also includes a BME680 environmental sensor.

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Can You Hack The RP2350? There’s $10,000 On The Line

August 12, 2024 by 63 Comments

The Raspberry Pi Foundation had their new RP2350 chip audited by Hextree.io, and now, both companies want to see if you can hack it. Just to prove that they’re serious, they’re putting out a $10,000 bounty. Can you get inside?

The challenge to hack the chip is simple enough. You need to dump a secret that is hidden at OTP ROW 0xc08. It’s 128 bits long, and it’s protected in two ways—by the RP2350’s secure boot and by OTP_DATA_PAGE48_LOCK1. Basically, the chip security features have been activated, and you need to get around them to score the prize.

The gauntlet was thrown down ahead of DEF CON, where the new chip was used in the event badges. Raspberry Pi and Hextree.io invited anyone finding a break to visit their booth in the Embedded Systems Village. It’s unclear at this stage if anyone claimed the bounty, so we can only assume the hunt remains open. It’s been stated that the challenge will run until 4 PM UK time on September 7th, 2024.

Hacking microcontrollers is a tough and exacting art. The GitHub repo provides full details on what you need to do, with the precise rules, terms, and conditions linked at the bottom. You can also watch the challenge video on Hextree.io.

Mouse Doesn’t Play Pong… It IS Pong!

August 8, 2024 by 1 Comment

From the “why didn’t we think of that” department comes [dupontgu’s] pong mouse project. The mouse appears and acts like a normal computer mouse until you click the scroll wheel. When you do, the mouse rapidly moves the cursor on the connected computer to play pong. Obviously, though, the paddles and the ball all look like your cursor, whatever that happens to be. So, how do you tell the score? Well, when a score happens, the cursor shows between the two paddles. In the middle means the game is tied. Otherwise, the player closest to the score indicator is winning. Continue reading “Mouse Doesn’t Play Pong… It IS Pong!” →

An ESP Makes A Bicycle Odometer

August 7, 2024 by 4 Comments

If you’d like to measure the speed of your cycling then it’s easy enough to buy a cycle computer, but as [Clovis Fritzen] has done it’s also an option to build one. The result of his work is a smart PCB on which the speed is indicated with a row of LEDs.

The sensor is a straightforward affair, a reed switch with a magnet on a wheel, which is sensed by an ESP8266. The six LEDs are charlieplexeed over three lines. To keep the supply voltage correct for the ESP from the uncertain state of a lithium battery, a small buck-boost module is used. Sadly the code doesn’t seem to make the speed available via the wireless part of the processor, but we’re guessing that a bit of extra software work could fix that.

The result when put in a box on the handlebars, is a smart but simple instrument that would aid any bike. It’s by no means the first one we’ve brought you and we doubt it will be the last.

You Can Program AVRs From The Commodore 64

July 26, 2024 by 10 Comments

These days, most of our microcontroller boards come with bootloaders so you can squirt hex into them straight over USB. However, you don’t need to do things this way. If you’re more old school, you can program your AVRs right from a Commodore 64. [Linus Akesson] shows us how.

Programming an AVR isn’t that hard. By holding the chip in reset, it’s possible to flash code via a serial protocol using just three wires. However, that’s pretty impractical to do with modern PCs — they don’t come with addressable IO pins anymore. Normally, you’d use a dedicated programmer to do the job, but [Linus] found his had died on a Friday night. So he set about turning his C64 into one instead.

He decided to use the pins of the C64’s Joystick Port 2, with pins 1, 2, 3, and 4 hooked up to SCK, MOSI, Reset, and MISO on the AVR, respectively. 5 V and Ground were also provided courtesy of the C64’s port. He then whipped up a simple bit of assembly code to read a bit of AVR hex and spit it out over the Joystick port following the in-circuit programming protocol. With a 1541 Ultimate to load files on to the C64 in hand, it was easy to pull his compiled AVR program off his modern PC, chuck it on the C64, and then get the old Commodore to program the AVR in turn.

It’s not the first time [Linus] has wowed us with a C64 in hand. If you’ve got your own fresh projects for the best-selling computer of all time, don’t hesitate to let us know!

Modern In-Circuit Emulator For The 6809

July 19, 2024 by 12 Comments

The Motorola 6809, released in 1978, was the follow-up to their 6800 from four years earlier. It’s a powerful little chip with many 16-bit features, although it’s an 8-bit micro at heart. Despite its great improvements over the 6800, and even technical superiority over the Z80 and 6502 (hardware multiply, for example!), it never reached the same levels of success that those chips did. However, there are still some famous systems, such as the TRS-80 Colour Computer, which utilized the chip and are still being hacked on today. [Ted] is clearly a fan of the 6809, as he used a Teensy 4.1 to create a cycle-exact, drop-in 6809 emulator!

A small interposer board rearranges the Teensy pinout to match the 6809, as well as translating voltage levels from 3.3V to 5V. With careful design, the Teensy matches the cycle diagrams in the Motorola datasheet precisely, and so should be able to run any applications written for the chip! A great test was booting Extended Colour BASIC for the TRS-80 CoCo 2 and running some test BASIC programs. Any issues with opcode decoding or timing would certainly be exposed while running an interpreted language like BASIC. After this successful test, it was time to let the Teensy’s ARM Cortex-M7 rip and see what it could do.

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