This little project aims to create a USB CD-ROM device. Unlike the typical deviced which tries to imitate this isn`t a real CD-ROM drive, it just emulates it. The idea is to allow the user to store a ISO image or other kind of CD-ROM image in a SD card to expose it as a CD-ROM to the computer. At the time of writing it works quite well, only teste
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d with ISO images and doesn`t allow hot extraction of the SD card. This will be fixed, but requires some tweaks on SCSI commands and responses in order to allow the host to eject the CD too. The schematic is prepared for media sensing, as represented by the switch connected to RB7. My SD card slots have 2 pins which get shorted when a card is inside the slot. The card works at 3. 3V so a 5V to 3. 3V converter is needed in case you want to supply the circuit with the USB voltage source. This is done by using a simple zener and a resistor. Be careful with the values and the power dissipated, some pieces may become hot! The device exposes a MSD to the USB host. You can have a look at Microchip examples for reference and the USB MSD spec. It`s important to use wireshark to debug the commands and their responses, this way you`ll know where the host gets stuck (typically when device sends bad respones the host keeps trying and trying over and over again triggering device resets too). The most important part are the SCSI commands. They are poorly documented for CDROM drives (as opposed to disk drives) so it`s crucial to have a reference to have a look. I used a Sandisk U3 pendrive which features CDROM emulation for storing internal programs (so they can`t be removed and can be autoruned!). I won`t get into details, just simple description. You need to fill the descriptors properly (have a look at a pen drive with wireshark and the...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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