The mechanical design of the Precursor RISC-V development kit #RISCV #Design @bunniestudios
Andrew “bunnie” Huang talks about mechanical design of the Precursor, a mobile, open hardware RISC-V System-on-Chip (SoC) development kit. Good mechanical design is hard and to put any extra into a design increases cost. It is informative to read how bunnie went about the design choices.
“Pocketability” is the difference between Precursor and naked PCB FPGA development platforms. We hope Precursor’s pocketability helps bring more open hardware out of the lab and into everyday use. Thus, the mechanical design of Precursor is of similar importance to its electrical, software, and security design.
After considering about a dozen or so mechanical layout scenarios, we arrived at the design shown above. Like every modern mobile device, when viewed by size and weight, Precursor is basically a battery attached to a display.
And on use of aluminum vice a plastic case:
Using aluminum for the bottom case allows us to shave about 1 mm (~15%) of thickness relative to using a polymer like ABS or PC at the expense of a fairly substantial increase in per-unit manufacturing costs. Although polymers are about twice the cost of aluminum by weight, an aluminum case costs about 10x as much to produce. This is because polymers can be molded in a matter of seconds, with very little waste material, whereas aluminum must be CNC’d out of a slab in a time-consuming process that scraps 80% of the original material. Surprisingly, the 10x cost-up isn’t the waste material; there is an efficient market for buying and recycling post-machining aluminum. Most of the extra cost is due to the labor required to machine the case which is orders of magnitude longer than the time required for injection molding.
Thus, while we could have made Precursor cheaper, we felt it would both be more pocketable, as well as more desirable, with the machined aluminum case: it would look more like a high-end mobile device, instead of a cheap plastic toy or remote control.
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.