Radical Brad over at the 6502.org forum has been working on this cool 7400 logic VGA video game system, Vulcan-74:
Video must be perfectly stable VGA, putting out 256 colors at a resolution of 400×300 using an 8 bit color space divided into RRR-GGG-BB
Video must include full 256 color 400×300 bitmapped screens with a seamless double buffer for high speed animations and high detailed images
The GPU system will include a high speed (20MHz) blitter system capable of dealing with moving variable sized bitmaps from a dedicated 1MB memory bank to the back buffer independent of the 6502 CPU. The entire GPU must be made ONLY of 7400 logic parts
The sound system will be minimum 4 independent digital sound channels, and include its own 1MB independent sample SRAM. Much like the Amiga, the sound system is independent of the CPU, and again all made with 7400 logic parts
The completed system must be capable of impressive games (Amiga quality), not just some simple tile engine. All games will load only from an external EEPROM (cartridge) via onboard 7400 logic based loader. No external processing will be allowed
The CPU will be a 65C02 only. No 65C16, as this is too new for my system! The 6502 will run at 16MHz minimum, using whatever IO decoding tricks I see fit. Bus pirating illegal opcodes, etc. Prelimanry tests have shown stable operation at 20MHz using a ROMless system running from 10ns SRAM
Today is a public holiday here in the UK, and Pi Towers is silent and still. Clive’s in a field “with no network (not even mobile),” he specifies, just in case someone were tempted to try and make him do something anyway. By the time this post appears, I’ll be pursuing a couple of kids around the Cambridge Museum of Technology. Liz and Eben have one-upped everyone by going to Scandinavia. So, in keeping with the leisurely, end-of-summer vibe of today, we thought we’d share a project that’s designed to amuse. We hope it’ll cheer up all those of you unlucky enough to live in places where you don’t automatically get to bunk off on the last Monday in August.
Raspython, a new project aiming to offer tutorials and learning resources for the Raspberry Pi community and for new makers and programmers in particular, brings us instructions for making Joker, a Raspberry Pi joke machine.
A fact that ought to be more widely known is that our own Ben Nuttall is founder and chairperson of the Pyjokes Society. He and co-founders Alex Savio, Borja Ayerdi and Oier Etxaniz have written pyjokes, a Python module offering lovingly curated one-liners for programmers, and it’s from this that Joker gets its material. Ben and friends encourage you to improve their collection by submitting the best programming jokes you know that can be expressed in 140 characters or fewer; you can propose them on GitHub via pyjokes’ proposal issue or via pull request.
Joker’s display is an affordable Adafruit 16×2 LCD Pi plate; this comes as a kit needing assembly, which Adafruit’s detailed instructions walk you through gently. With the LCD assembled and mounted, getting Joker up and running is just a matter of installing the pyjokes module, LCD drivers and Joker script, together with a little bit of other set-up to allow your Raspberry Pi to talk to the LCD.
Everything you need is in the tutorial, and it makes for a really great self-contained project. Give it a whirl!
Application note regarding proper usage of LDO from Analog Devices. Link here (PDF)
A low dropout (LDO) regulator is capable of maintaining its specified output voltage over a wide range of load currents and input voltages, down to a very small difference between input and output voltages. This difference, known as the dropout voltage or headroom requirement, can be as low as 80 mV at 2 A.
Current portable devices often require up to 20 low dropout linear regulators. Many of the LDOs in today’s portable devices are integrated into multifunction power management ICs (PMICs), highly integrated systems with many power domains for audio, battery charging, housekeeping, lighting, communications, and other functions.
As portable systems rapidly evolve, however, the integrated PMIC cannot keep up with peripheral power requirements. Dedicated LDOs must be added in the later stages of system development to power such optional items as camera modules, Bluetooth®, WiFi®, and other bolt-on functions. LDOs have also been used to reduce noise, to solve voltage-regulation problems caused by electromagnetic interference (EMI) and printed circuit board (PCB) routing, and to improve system power efficiency by switching off unneeded functions.
This application note reviews the basic LDO topology, explains key specifications, and shows the application of low dropout voltage regulators in systems.
We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:
Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
Facebook PCB Friday. Free PCBs while you wait for the weekend
Old but still good technical note from Analog Devices on USB isolation. Link here (PDF)
Currently, iCoupler® digital isolation technology is capable of transferring data at rates ranging from DC to about 150Mbps, which is adequate for transferring serial data to support low (1.5Mbps) and full (12Mbps) speed modes of USB. There are three places where isolation could be introduced, in the differential transmission lines D+/D–, between the controller and the transceiver, and between the controller and the system controller. Unfortunately, the trend toward higher levels of integration incorporates the transceiver and controller interfaces into the system controller, leaving only D+/D– data lines available outside of the controller for isolation.
This is an extremely challenging place to try isolation because there is no flow of control signals, and data is a combination of single ended and digital signaling. With current isolation technology, the most practical place to isolate is between the system controller and a stand-alone USB controller/transceiver where signals can be unidirectional and logic level. In many cases this means bypassing inboard controllers and adding a discrete USB controller.
An application note (PDF!) from NXP on how to calculate the power dissipated by the triac:
This Application Note describes how to calculate the power dissipation for triacs and Silicon Controlled Rectifiers. Thermal calculations are also included to help the circuit designer to predict the maximum junction temperature or calculate the required heatsink thermal resistance. Four
worked examples ensure that all the power and thermal questions that arise during the design process are covered.