The other day I found myself with a Rasberry Pi that I wanted to use but I had forgotten my FTDI UART cable. What I did have is my Bus Pirate v3.6 and I found it was pretty easy to use it’s transpartent UART bridge macro to connect to the Pi.
In this project you’ll create a standalone web server with a Raspberry Pi that can toggle two LEDs. You can replace those LEDs with any output (like a relay or a transistor).
In order to create the web server you will be using a Python microframework called Flask.
Joonas Pihlajamaa from Code and Life writes, ” I’ve previously made a GPIO benchmark of Raspberry Pi 1 and 2, and have always wanted to see how BeagleBone Black would stack against the Pis. I recently got one so the obvious thing to do was to see how fast the little thing could go. Turns out, the little thing needed a bit more work than the Pi, but the results were quite interesting.”
In 2013 the dean of an Ethiopian university addressed Maker Faire Hannover and outlined one of his concerns; that the high price of developed-world textbooks was holding back the cause of education for universities such as his own in developing countries. He was there to ask for help from the maker community to solve his problem, and a group of his audience took up the challenge to create an affordable and accessible automatic book scanner.
Their scanner builds on the work of Google engineer [Dany Qumsiyeh], whose open source linear book scanner turns pages by traversing the opened book over a triangular prismic former such that pages are turned by vacuum as they pass over carefully designed slots in its surface. Their modification replaces the vacuum with the Coandă effect, to more gently tease open each page and it is hoped reduce the chance of damaging the volumes being scanned.
The whole machine is controlled by a Raspberry Pi, and the scanning is performed by linear scanning optics, sensors, and electronics taken from flatbed scanners.
An important design goal of the project was to ensure that the scanner could be built without special tools or expertise that might be difficult to find in a developing country, as well as that it should be as inexpensive as possible. The frame of the machine is off-the-shelf extruded aluminium, and the body is acrylic sheet which can be cut to shape with a hand saw if necessary. It is estimated that the device will cost in the region of 500 Euros (about $568) to build.
Writing from the perspective of having been peripherally involved in a professional book scanning operation at a large publisher the benefits of this machine are immediately apparent. Removing the binding and automatically scanning each page as an individual sheet produces a very fast and high quality result, but by its very nature damages the volume being scanned. This machine promises to deliver a solution to the problem of book scanning that is considerably less intrusive.
It is also worth noting that the project does not address any copyright issues that might arise from scanning commercially published textbooks, though this is more of a concern for the end user in terms of what they scan with it than it is for the maker.
I recently inherited a key on board (KOB) telegraph that my late grandfather used to practice Morse code with when he was a kid (Figure 1). A little bit of curiosity of how it would work and a little bit of displeasure from seeing it sit and collect dust, I began a journey to resurrect the old machine and develop some software to bring it into the digital age.
The Raspberry Pi is a very capable device whose hardware has been pushed to the limit in all sorts of interesting ways. But even the most ingenious of experimenters have to agree on one point; it doesn’t possess an analog-to-digital converter. If you want analog inputs you will have to buy or build them.
[Mincepi] has done just that, but not as you might expect by adding an integrated circuit on one of the Pi’s interfaces. Instead the circuit [Mincepi] is using consists only of passive components, measuring the time taken to discharge the parasitic capacitance of one of the Pi’s inputs from logic 1 voltage to logic 0 voltage through a resistor into the voltage to be measured. This is a long-established approach to A to D conversion, one that was achieved back in the day with purpose-designed timers as microprocessor ancillaries.
The problem is that the Pi does not have a timer peripheral, so [Mincepi] has used the shift registers that form part of the Pi’s SPI and PCM inputs to perform this task on two channels. A sample rate of 100kHz and 6-bit resolution is claimed, with enough voltage range for a 1V peak-to-peak audio signal to be sampled.
Of course, simplicity does not guarantee a good ADC, and this circuit does not perform very well. It is noisy, non-linear, and as [Mincepi] puts it, probably sensitive to temperature. And though [Mincepi] talks in detail about the software to drive it, none is forthcoming. To quote: “It doesn’t include code since I’m in the process of writing a proper sound device module. My previous code was a simple character device, but it worked just fine, and served to prove the concept.”
We really want this to work, even if it’s not the best ADC ever. So we eagerly await the sound device module, and look forward to more news from the project.