Re: [Sdcc-user] Alternates to Atmel 89C55WD

[jon <jo...@jo...>]

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....

Jon