For several years, [Ray] and [Anna], the team behind ElectroSmash, have been smashing audio electronics and churning out some sweet DIY audio gear. This time around, they’ve built Pedal-Pi — a simple programmable guitar pedal based around the Raspberry-Pi Zero. It is aimed at hackers, programmers and musicians who want to experiment with sounds and learn about digital audio. A lot of effort has gone in to documenting the whole project. Circuit analysis, a detailed BoM, programming, assembly and background information on related topics are all covered on their Forum.
The hardware is split in to three parts. On the input, a MCP6002 rail-to-rail op-amp amplifies and filters the analog waveform and then a MCP3202 ADC digitizes it to a 12-bit signal. The Pi-Zero then does all of the DSP, creating effects such as distortion, fuzz, delay, echo and tremolo among others. The Pi-Zero generates a dual PWM signal, which is combined and filtered before being presented at the output. The design is all through hole and the handy assembly guide can be useful for novices during assembly. The code examples include a large number of pedal effects, and if you are familiar with C, then there’s enough information available to help you write your own effects.
Even if you don’t plan on building one, technical background such as the Basics of Audio DSP in C for Raspberry Pi Zero, Using MCP3202 ADC with Raspberry Pi Zero and PWM Audio on Raspberry Pi Zero ought to make for interesting reading. Check out the video after the break detailing the build.
If you’d like to check out some of their earlier work, check out 1WAMP, an Open Hardware Guitar Amplifier and pedalSHIELD, an opensource Arduino Guitar Pedal.
Continue reading “Pedal-Pi, simple programmable guitar pedal”
There are hundreds of ARM-based Linux development boards out there, with new ones appearing every week. The bulk of these ARM boards are mostly unsupported, and in the worst case they don’t work at all. There’s a reason the Raspberry Pi is the best-selling tiny ARM computer, and it isn’t because it’s the fastest or most capable. The Raspberry Pi got to where it is today because of a huge amount of work from devs around the globe.
Try as they might, the newcomer fabricators of these other ARM boards can’t easily glom onto the popularity of the Pi. Doing so would require a Broadcom chipset. Now that the Broadcom BCM2835-based ODROID-W has gone out of production because Broadcom refused to sell the chips, the Raspberry Pi ecosystem has been completely closed.
Things may be changing. ArduCAM has introduced a tiny Raspberry Pi compatible module based on Broadcom’s BCM2835 chipset, the same chip found in the original Raspberry Pis A, B, B+ and Zero. This module is tiny – just under an inch square – and compatible with all of the supported software that makes the Raspberry Pi so irresistible.
Although this Raspberry Pi-compatible board is not finalized, the specs are what you would expect from what is essentially a Raspberry Pi Zero cut down to a square inch board. The CPU is listed as, “Broadcom BCM2835 ARM11 Processor @ 700 MHz (or 1GHz?)” – yes, even the spec sheet doesn’t know how fast the CPU is running – and RAM is either 256 or 512MB of LPDDR2.
There isn’t space on the board for a 2×20 pin header, but a sufficient number of GPIOs are broken out to make this board useful. You will fin a micro-SD card slot, twin micro-USB ports, connectors for power and composite video, as well as the Pi Camera connector. This board is basically the same size as the Pi Camera board, making the idea of a very tiny Linux-backed imaging systems tantalizingly close to being a reality.
It must be noted that this board is not for sale yet, and if Broadcom takes offense to the project, it may never be. That’s exactly what happened with the ODROID-W, and if ArduCAM can’t secure a supply of chips from Broadcom, this project will never see the light of day.
A few years ago, Broadcom had a pretty nice chip – the BCM2835 – that could do 1080 video, had fairly powerful graphics performance, run a *nix at a good click, and was fairly cheap. A Broadcom employee thought, “why don’t we build an educational computer with this” and the Raspberry Pi was born. Since then, Broadcom has kept that chip to themselves, funneling all of them into what has become a very vibrant platform for education, tinkering, and any other project that could use a small Linux board. Recently, Broadcom has started to sell the BCM2835 to anyone who has the cash and from the looks of it, real Raspberry Pi clones are starting to make their way into the marketplace.
Other Raspberry Pi clone boards out there like the Banana Pi and the HummingBoard don’t use the same BCM2835 found in the Raspi and the new Odroid. The new board also has the same 26 pin GPIO expansion socket, and runs the same binaries as the Raspberry P;. It is a clone in every sense, with a slightly different form factor geared towards very tiny, portable, and battery-powered use cases.
Unlike the official Raspberry Pi Compute Module, the Odroid isn’t meant to be used as a system on module, shoved into any product that needs a fast-ish ARM core without needing engineers to actually design a circuit with an ARM. The Odroid is a cut-down, extremely minimalist version of the Raspi, perfect for any project where space is at a premium.
There are a few interesting features included on the Odroid: there’s an on-board battery connector, a real-time clock on the board, and more of the BCM2835 GPIOs are exposed (although not the same ones as the upgraded RPi Model B+). There’s no Ethernet, but odds are if you’re building something that’s battery-powered, you won’t need that anyway.
As far as price goes, you can pick one of these Odroids up for $30 USD, with $9 shipping from South Korea. That’s pretty comparable to the price of a real Raspberry Pi, but if the features in the Odroid are worth it to you, it might be a worthwhile clone.