On 08/31/2013 01:11 AM, jon wrote:
> On Fri, 2013-08-30 at 18:56 -0400, Dave McGuire wrote:
>> On 08/30/2013 02:20 PM, jon wrote:
>>>> Thanks to all that replied to my shockingly newbie question! I googled
>>>> more and found the answers I needed. I love SDCC! But all of my work
>>>> with SDCC so far has been Z80 because I've worked with Z80 for well
>>>> over 25 years now.
>>>>
>>>> I wanted to switch to more modern chips. I liked the Atmel 89C55WD
>>>> because it has four IO ports plus 24K flash and 256 SRAM. It seemed to
>>>> be darn cheap for all of what it has built in.
>>> If your going to go modern then why not use an ARM core. STM32 for
>>> example.
>>>
>>> I used to program Z80 on CP/M, then Z80 on embedded boards. These days I
>>> don't bother with anything much smaller than a full ARM board with
>>> Linux. The price of ARM SOC is so low, compare a beagle board or
>>> Raspberry Pi or one of the generic ARM boards what other hardware you
>>> can buy for the money and its a no contest. Plus having a linux kernel
>>> gives me networking, filesystems, displays etc.
>>
>> ...and a rather dramatic amount of complexity to control eight relays.
>> Good heavens. I think I need a stiff drink after reading that.
>
> Ah you say that but if the application is "ethernet controlled relays"
> then :
>
> 1) For small volumes the cost is low, probably lower than making your
> own PCB with a piffy micontroller with tacked on ethernet. I have done
> this several times and I stand by the statement "tacked on".
> 2) The software is piss easy to debug and can be self hosting for
> tweaking. Requirement is an SSH or telnet client from any old machine.
> I don't even bother to take a laptop to client sites as I can always
> install a free windows ssh client (putty) when I arrive at the
> customers, MAC and linux already have one as default.
> 3) Did I mention the price ?
> 4) The relay application for example would not really require much in
> the way of custom software. The GPIO lines can be toggled from user
> space, an HTTP server with a few line of user script, I really do mean a
> few lines <10 in total maybe for a basic:
> http://myboard/realay.cgi?realy=4&state=on
> style interface.
>
> I use Microcontrollers for some things but my personal rule of thumb is
> that if the application requires ethernet then just use an ARM board.
> Its not like you can ever run out of power with a typical >=500MIPS,
>> =256MB RAM, >=2GB of backing storage etc.
>
> Power consumption is a non issue as well. An older CPU style with some
> peripherals and a linear regulator is on a par with a modern ARM board
> if using a switching regulator (buck converter). Also if power is a
> concern you can underclock the ARM boards typically just by tweaking a
> register or two using a utility.
>
> It sounds mad, but from the developers point of view the "complexity" is
> far far far less. I could knock up a basic ethernet controlled 8
> channel relay box in about an hour, make it first rate in 5. It would
> take me much longer to lay out a PCB. I no longer develop on strip
> board, work of the devil !
>
> An ARM board is much less complex than unpacking and setting up my PIC
> dev kit and get all the ducks lined up to start work.
>
> For low volume I would buy pre-build modules from the far east.
> http://www.ebay.co.uk/itm/RASPBERRY-Pi-Model-B-revision-2-0-Board-512MB-RAM-The-Very-Latest-/170939155187?pt=UK_Computing_Other_Computing_Networking&hash=item27ccc482f3
> http://www.ebay.co.uk/itm/ItS7DC-DC-Converter-Buck-Step-down-Module-Voltage-LED-Power-3A-12V-To-5V-3-3V-/141049238853?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item20d7309545
> http://www.ebay.co.uk/itm/New-8-Channel-5V-Relay-Module-Board-for-Arduino-PIC-AVR-MCU-DSP-ARM-UK-/151105724470?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item232e9a6036
> http://www.ebay.co.uk/itm/231025835930?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
>
> For a higher volume product I would use an STM32 with built in ethernet
> (not linux) an "RJ45 socket and magnetics" module on a custom PCB with
> buck converter PSU section. This would be a reasonable compromise
> between cost and complexity and much more powerful than a typical
> PIC/Atmel ethernet combo and less problematic.
>
> Just my 2c worth :-) Other may agree to differ....
Well...I work as a design engineer, usually on industrial control
applications. Complexity is the enemy of stability, and unnecessary
complexity is a design flaw...that's my usual mindset. Cost is often a
secondary consideration for anything other than bulk consumer
electronics. When a bug in someone else's huge volume of code can
result in a multi-hundred-ton machine to jerk in the wrong direction and
kill people, and it comes down on ME, I don't want anything but the bare
minimum on the board that controls it.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
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