Open Hardware: Arduino, Raspberry Pi, and ESP32
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Building a DIY laser modem | Arduino Blog
All digital communication ultimately comes down to transmitting ones and zeroes, but there are many ways to achieve that. One can encode that binary data as modulation in a radio signal or simply pulse electricity through a wire. But one of the most interesting methods is optical. Flashing a light is a great way to transmit data over long distances at high speed. Fiber optic cables are the most common medium, but it is also possible to shine light through open air. To demonstrate this concept, Nino Ivanov built his own laser modem.
In theory, this should be a very straightforward device: just point a laser at a photoresistor. Pulse the laser so that it is on for ones and off for zeroes. Then measure the resistance of the photoresistor to read those ones and zeroes. But as Ivanov explains, there are two issues with this setup. The first is that photoresistors are slow to respond to light changes and that severely limits the data transmission speed. The second issue is that it isn’t always obvious what is a zero bit (no light) and what is an absence of data transmission altogether.
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Pico railway clock
Martin and Vanessa had purchased what was essentially a secondary clock – ineffective without a mother clock. To get it working, they decided to build a mother clock themselves with a few additional components and some code running on a Raspberry Pi Pico microcontroller.
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Bombercat is a security tool that combines an RP2020 and an ESP32 MCUs
The BomberCat board by ElectronicCats is a device powered by an RP2040 chip and a ESP32 microcontroller. According to the company, this security tool supports NFC technology and magnetic stripe technology. Moreover, the board was specially created to audit, read or emulate magnetic stripes and NFC cards.