19"-3U Microcontroller  - Page 1
Forum section: electronics / projects

author: homebrew
author_rank: Frequent Contributor
timestamp: October 07, 2013, 11:56:53 am
content: Hello eevbloggers,I'm not a professional electronic engineer but I'm doing microcontroller projects (8051, AVR, ARM) since more than a decade in my spare time now. And I'm new to the forum ...Anyway … for future projects I want to build a component-like system based on standard Euro-cards for use in standard 3U-19"-chassis with a bus backplane. I plan to have only one master cpu card per bus.The rest of them should be I/O-hardware only. I think that 10-20 Mbit bus transfer bandwidth should be enough for everything I do have in mind right now.I basically have two questions where expert input would be appreciated:1) Regarding the backplane: What bus should I use? Currently I'm looking into STE-Bus (yeah, it is more than two decades old) as I do have the specifications of it (IEEE-standard) and it seems to be fairly doable interfacing it using standard TTL-logic chips or low grade CPLDs only.However, the bus protocol is far beyond my requirements for a single-master I/O-bus. Maybe just Data/Address/IRQ and a Read/Write signal would be enough. So what do you think? Using a non standard but simpler bus or implementing a full featured STE-bus? Or doing something completely different? VME or CPCI absolutely seams out of range ...2) Regarding the CPU for the master board. Currently I think about using an old-fashioned 8051 (maybe from dallas as they provide very fast pin equivalent 8051 clones). Why? Because 8051s are source able from several vendors, they can run code from external bus (in contrast to AVR's), they come in through hole packages and they have a very simplistic architecture that is easy to comprehend.All in all, when really building this, I would open source it to enable the formation of a community around it designing and building further cards for the system.So what you think? Is this a good idea or just 20 years outdated and doomed to fail right from the beginning?Best,Peter

author: jechavarria
author_rank: Newbie
timestamp: October 07, 2013, 12:08:04 pm
content: Hi!About your questions, all depends of the final use of your equipment. In my work, we usually use this kind of cards and backplanes. We usually use serial buses, most of the time we use I2C buses. This bus only uses two lines and you can communicate a lot of devices, such ADC's, DAC's, IO expansors, other microcontrollers...CAN Bus, SPI, RS485, are another serial options. About the microcontroller, again it depends of your application. I usually use this kind of microcontrollers in my projects (http://www.jechavarria.com/2013/03/25/dseta-board-a-cpu-based-on-the-atmel-at89c51re2/). In the past, I work with the DS89C4x0 Dallas family, but in the last time, I use the Atmel ones, and works also fine.I hope some of this helps you. If you want, send me a mail and we can discuss more about it. Good luick!!

author: homebrew
author_rank: Frequent Contributor
timestamp: October 07, 2013, 05:38:45 pm
content: Thanks jechavarria,never really thought of running a serial bus through a backplane but that comes only from my limited knowledge of industry projects of that type. Maybe SPI would be a good idea in addition to some slave-select lines and some sort of interrupt system...I clearly had hobbyist benchtop lab-equipent in my mind. Like high(er) resolution ADCs, DDS-function gens, EEPROM-programmers, DIO-boards, maybe even a (very) simplistic DSO etc.Peter

author: tszaboo
author_rank: Super Contributor
timestamp: October 07, 2013, 06:43:25 pm
content: If you want my honest opinion, this system is doomed to failure, or broader acceptance. (opinion) Using a 8051 in the 21 century is not cool. You need some coolness factor for community. (opinion) The 3U rack is crazy big. Not everyone wants to store a 10+ KG rack on their desk, and the rack itself is not cheap. (opinion) The connectors are expensive, as they have too much pins. The PCB will be expensive. Eurocard is a fine size, and everithing fits, but even in china you will pay 50-100 EUR for single quantities (just checked pcbcart). If you have 10 different boards and 2 revisions that is 2000 EUR+ just for one sets of boards.And you need the backplane, additional cost.Hovewer, I wouldn't give it up. Use serial bus, as already suggested. Use smaller PCBs. 5*5 CM ( or 5*10CM )is good for a lot of stuff, and it costs almost nothing to make compared the eurocard. Use plain simple 100 mil headers. Use something better than the 8051, there are some other, not mainstream architecture out there (pic32, c2000...) if you dont want yet an other avr/arm/pic project. (end of opinion)

author: luidoltp
author_rank: Newbie
timestamp: October 07, 2013, 07:54:53 pm
content: Hi,Quote from: homebrew on October 07, 2013, 05:38:45 pmwhen I read your intention, I couldn't help but think of the "c't Lab". It sounds quite similar to the system you are planning.I sadly wasn't able to find any description in English ... so Google has to do the job:http://translate.google.com/translate?sl=auto&tl=en&prev=_t&hl=en&ie=UTF-8&u=http://www.heise.de/ct/artikel/Fernwirkung-291012.htmlOn the following website you find an overview of all the modules they built. Just click on the publications and then "Online Sample" (you will get the full text).http://translate.google.com/translate?hl=en&sl=de&tl=en&u=http%3A%2F%2Fwww.heise.de%2Fct%2Fprojekte%2Fc-t-Lab-Bausteine-zum-Messen-Steuern-und-Regeln-284113.html&sandbox=1Modules they have built are ADC, DAC, Multimeter, Power supply, Electronic load, Frequency generator, ...All schematics, layouts, partlists, ... are available athttp://www.heise.de/ct/projekte/machmit/ctlab/browserBest,Lui