标签: 32bits

At the recent Maker Faire in California, USA, the new Arduino development board based on Atmel's 32bit ARM based SAM3X8 was shown. Now available for use by do-it-yourself enthusiasts and professional developers, the new board is called the Arduino Due and is based on an Atmel ARM Cortex-M3 processor-based MCU, also known as the Atmel SAM3 MCU. Because it is still undergoing beta testing within the Arduino community, the cost of the Due to the public has not been set. The big question is whether it will only be of interest to designers comfortable with doing application development on 32bit platforms or whether there is enough there to move the large base of hobbyists who have been doing designs with the now familiar 8 bit MCUs. As with previous 8bit Arduino boards, the Due platform is targeted at home automation projects and can run up to 96MHz, three times the clock speed of any other of the Atmel MCU based boards now available. Two other Arduino components have also been released for use by the community: * Arduino WiFi Shield. Built for WiFi applications, the Arduino WiFi shield is powered by Atmel's AVR UC3 MCU based its proprietary 32bit RISC architecture and a HD wireless module, and provides developers a powerful WiFi interface. * Arduino Leonardo. Based on the Atmel 8bit megaAVR ATmega32U4, the Arduino Leonardo is a low-cost Arduino board. It has the same shape and connectors as the UNO but it has a simpler circuit. On the software side it has a USB driver able to simulate a mouse, a keyboard, and a serial port. The new 32bit ARM based Due board is not the first one developed to provide a pathway for hobbyists to migrate from the original 8bit AVR form factor to a 32bit MCU. Several other 32bit based platforms are what are called "duinos,"—boards and components which are compatible, but do not fully satisfy the Arduino community definition. Among the 32bit processors used in these "duino" boards are the Firebird32, based on Freescale 32bit Coldfire MCF51JM128; the FezDomino, an ARM-based platform from GHI Electronics; the 48MHz 32bit ARM7 Netduino; the Bugblat, based on ST Micro's ARM Cortex-M3-based MCU; Freescale's Kinetis-L ARM Cortex-M0+ Freedom and Leaflab's Maple, based on STMicro's 32bit ARM MCU. Developers using the new 32bit ARM-based Due will have all of the same software development tools—the open source C++ based Wiring language and the Processing IDE, a cross-platform application written in Java—currently available on most of the current 8bit Atmel platforms. The Arduino IDE uses the GNU tool chain and AVR Libc to compile programs. Also available at no cost from Atmel is the cross hardware platform Studio 6, a.full-featured IDE and software development system for use across all of Atmel's AVR 8bit, AVR 32bit, and SAM (ARM-based) 32bit MCUs, processors. Certainly the cost of the board will be important to the Arduino audience, made up as it is by an eclectic mix of artists, designers, hobbyists, and anyone interested in DIY projects, for whom both cost and ease of use are equally important. Studio 6 will be a good first step toward helping such "knowledge domain enthusiasts" ( DIYers who have an idea and want to build it with a minimum of fuss ) make the transition from the simpler 8bit environment to the inherently more complex 32bit programming venue a bit easier.  

In a recent article, Mike Barr predicts that 32 bit processors will eventually beat or match 8 bitters. I well remember meeting with an analyst around 1990 who told me with great certainty that 8 bits was dead and everything would be, in the near future, 32 bits. Reponses to Mike's article are interesting and argue passionately for both sides of the issue. Chuck Manning thinks that decreasing 32 bit prices will push down their smaller brethren as well. I've made this argument many times in the past. When you can get an 8 bitter for a penny whole new applications will open that we can't imagine today. Chuck also notes that byte-wide processors eat less power, and can tolerate wider power supply voltages than 32 bitters. This is true, and low power is certainly a holy grail of the industry. But I can't see any reason why, sometime in the future, all CPUs won't run off just about any source of energy. Miro Samek says "8bitters make no sense." Part of his argument is that the CPU itself is just a tiny part of a typical microprocessor. Most of the real estate is devoted to memory and peripherals. This is a great argument. Except it's couched in the present tense and is therefore incorrect. Today you can buy an 8 bitter for a third (or less) than the cheapest 32 bit part on the market. That's irrelevant for some applications yet life and death for others. In the future I expect this will change. A Cortex-M0+ in 40 nm geometry requires less than 0.01 square mm of floor space. The CPU itself will eventually truly be an insignificant factor in the transistor budget or die size. But there are three conflicting and confusing trends that toss a little sand into this discussion. First, many low end parts are built with fully-depreciated "antique" fabs at geometries that are almost laughable today. Until and unless parts built with more modern processes have paid for their multibillion dollar fabs, there will be a cost rider associated with the parts. Second, there's another cost that won't go away. Let's face it: the future of 32 bit microcontrollers is ARM, and ARM collects a tax on each part sold. Those numbers are closely guarded, but I have heard rumors that for Cortex-style devices they run tens of cents. Even if all of the other costs were zeroed out, these devices can't compete in the most price sensitive applications. I've long thought that ARM's biggest competitor is the one that doesn't exist yet: a royalty-free open-source CPU supplied with all of the design support ARM provides. Will this happen? Probably. Will it be successful? One trend in the semiconductor industry has been a move away from support of proprietary tools in favor of the freebies, so an open-source CPU would certainly fit the manufacturers' models. But it's hard to see how a free movement can create the huge, mostly compatible, ecosystem ARM provides. Third, silicon costs will continue to drop until they become a non-issue for low-end microprocessors. The package will be where all of the money goes, and there's no reason why high- and low-end microcontrollers won't have the same pinouts and packages. Think a six-pin Cortex part. So, the first and third arguments suggest 32 bits won't cost any more than 8 bitters. The wild card is the second, and it's hard to see how that will play out. I do disagree with Miro's statement "I think that 8bitters still thrive only because of powerful non-technical reasons, such as the immense intellectual inertia of the embedded community." No doubt some of that is true, but costs still drive engineering decisions. There's the parts cost, but also that of tools. I've worked a lot recently with ARM's very nice IDE, but it costs thousands of dollars. Microchip, in contrast, makes PIC tools available for practically nothing. Sure, you can get GCC for ARM and set up your own environment, but that takes time and more expertise than a lot of low-end developers possess. And some teams demand the support they get from a vendor. So will 32 bitters win? Probably, as Mike originally said, in the vast majority of applications. Will that be soon? I doubt it.