Which controller to use?

As a coder I've usually had custom hardware to work with and
the choice of architecture etc has been cost-driven and set
in stone long before I start trying to debug the board...
but I digress.

I have a potential project coming up, where I may have 
some influence on the hardware.  The spec is of necessity
still slightly woolly, so my apologies for that in advance.

The basics are 
input - RFID tags, info probably read over RS-232
output - solenoids / relays to turn a motor on
I/O - USB memory stick to upload new settings, download reports
control panel - three buttons and possibly a cheap LCD display
optional - WiFi interface
weatherproofed - will operate outdoors, off 12V DC

ROM / RAM / CPU requirements are going to be modest by today's
standards.  We're talking about, say, 200 RFID tags to recognise,
each of which has an individual setting for the amount of time
to turn the relay / solenoid on for.

So any suggestions for a single board microcontroller that'd
provide the above at reasonable cost, with the minimum of hassle,
with a (preferably free) C toolchain?

Personally I think the idea of a USB port on an outdoor piece
of equipment is a bit nuts, so any suggested alternatives?
Bluetooth?

On 5/4/2010 2:01 PM, FJG wrote:
> As a coder I've usually had custom hardware to work with and
> the choice of architecture etc has been cost-driven and set
> in stone long before I start trying to debug the board...
> but I digress.
>
> I have a potential project coming up, where I may have
> some influence on the hardware.  The spec is of necessity
> still slightly woolly, so my apologies for that in advance.
>
> The basics are
> input - RFID tags, info probably read over RS-232
> output - solenoids / relays to turn a motor on
> I/O - USB memory stick to upload new settings, download reports
> control panel - three buttons and possibly a cheap LCD display
> optional - WiFi interface
> weatherproofed - will operate outdoors, off 12V DC
>
> ROM / RAM / CPU requirements are going to be modest by today's
> standards.  We're talking about, say, 200 RFID tags to recognise,
> each of which has an individual setting for the amount of time
> to turn the relay / solenoid on for.
>
> So any suggestions for a single board microcontroller that'd
> provide the above at reasonable cost, with the minimum of hassle,
> with a (preferably free) C toolchain?
>
> Personally I think the idea of a USB port on an outdoor piece
> of equipment is a bit nuts, so any suggested alternatives?
> Bluetooth?

USB in any embedded device is a bit nuts, but I digress.

You are not going to find USB master on a poor 8/16-bit micro.

Only 32 bit devices have USB master.

So, if you think your doing to get it cheap........

Everything else is doable with any micro-controller ( or two ).

Google for WinAVR, free tool chain and Atmel AVR family is very robust.

I have done two products with these tools.

hamilton

On 5/4/2010 1:17 PM, hamilton wrote:

 > [snip]
 >
> You are not going to find USB master on a poor 8/16-bit micro.
>
> Only 32 bit devices have USB master.
>
> So, if you think your doing to get it cheap........
>
 > [snip]

You mean like a Cortex-M3 for south of $2, or a Cortex-M0 for south of $1?

-- 
Rob Gaddi, Highland Technology
Email address is currently out of order

On May 4, 1:40=A0pm, Rob Gaddi <rga...@technologyhighland.com> wrote:
> On 5/4/2010 1:17 PM, hamilton wrote:
>
> =A0> [snip]
> =A0>> You are not going to find USB master on a poor 8/16-bit micro.
>
> > Only 32 bit devices have USB master.
>
> > So, if you think your doing to get it cheap........
>
> =A0> [snip]
>
> You mean like a Cortex-M3 for south of $2, or a Cortex-M0 for south of $1=
?

Not with usb host.  With host functions, pins and costs go up, not
that they are correlated.

>
> --
> Rob Gaddi, Highland Technology
> Email address is currently out of order

hamilton wrote:

<snip>

> Only 32 bit devices have USB master.
>
> So, if you think your doing to get it cheap........

I'm sure 32 bits is fine.

> Everything else is doable with any micro-controller ( or two ).

Sure.  What I'm looking for is a module / single-board computer / 
whatever you want to call it that will provide as much out of the
box as possible.  Even some sort of "hobbyist" kit would be fine
if it provided 12V relays for controlling motors, debounced buttons,
a small LCD output, etc.

E.g. http://rabbit.com/ is under consideration.

FJG wrote:
> As a coder I've usually had custom hardware to work with and
> the choice of architecture etc has been cost-driven and set
> in stone long before I start trying to debug the board...
> but I digress.
> 
> I have a potential project coming up, where I may have 
> some influence on the hardware.  The spec is of necessity
> still slightly woolly, so my apologies for that in advance.
> 
> The basics are 
> input - RFID tags, info probably read over RS-232
> output - solenoids / relays to turn a motor on
> I/O - USB memory stick to upload new settings, download reports
> control panel - three buttons and possibly a cheap LCD display
> optional - WiFi interface
> weatherproofed - will operate outdoors, off 12V DC
> 
> ROM / RAM / CPU requirements are going to be modest by today's
> standards.  We're talking about, say, 200 RFID tags to recognise,
> each of which has an individual setting for the amount of time
> to turn the relay / solenoid on for.
> 
> So any suggestions for a single board microcontroller that'd
> provide the above at reasonable cost, with the minimum of hassle,
> with a (preferably free) C toolchain?
> 
> Personally I think the idea of a USB port on an outdoor piece
> of equipment is a bit nuts, so any suggested alternatives?
> Bluetooth?

If you want success, you MUST make sure that the hardware you specify 
can do everything you ask of it.  This is not a trivial task if you 
don't want to way overdesign the processor.  Find out everything that 
the thing needs to do, budget the RAM/ROM/bandwidth for it, determine if 
it has to be done simultaneously with everything else, and work from there.

Asking the thing to be a USB host -- as pointed out -- will drive the 
cost up.  _If_ you can find a USB host stack (check with Micrium) that 
will run on an 8/16 bit processor, it'll require more processor 
resources (maybe someone will chime in, with experience?).

Talking to SD cards has a _much_ lighter footprint, although you still 
have the connectors outdoors issue.

You can buy Bluetooth modules; if you can find one that doesn't put too 
much strain on the processor this may be way less expensive than USB, 
and is contactless.

-- 
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Am 04.05.2010 22:01, schrieb FJG:
> As a coder I've usually had custom hardware to work with and
> the choice of architecture etc has been cost-driven and set
> in stone long before I start trying to debug the board...
> but I digress.
>
> I have a potential project coming up, where I may have
> some influence on the hardware.  The spec is of necessity
> still slightly woolly, so my apologies for that in advance.
>
> The basics are
> input - RFID tags, info probably read over RS-232
> output - solenoids / relays to turn a motor on
> I/O - USB memory stick to upload new settings, download reports
> control panel - three buttons and possibly a cheap LCD display
> optional - WiFi interface
> weatherproofed - will operate outdoors, off 12V DC

You really should try to replace the USB memory stick by a MMC/SD card. 
USB is a rather complicated interface, and for using USB sticks you'd 
need to implement an USB host, which is even two magnitudes more complex 
than an USB device.
Just say no! Don't do it.

MMC cards are rather simple to talk to. SD cards are basically MMC cards 
plus copy protection mechanisms, so just use them as MMC cards.

> So any suggestions for a single board microcontroller that'd
> provide the above at reasonable cost, with the minimum of hassle,
> with a (preferably free) C toolchain?

The processor core doesn't matter much. Choose your controller by the 
built-in peripherials needed.

The really cheap segmented bare LCD glasses found in clocks and 
calculators need a special peripherial, but there are enough controllers 
that have that already built-in.

If you compare prices you'll notice that there is little difference 
between bigger 8 bit controllers and the smaller 32 bit controllers, 
which are much faster.

Families to look at:
AVR (very C friendly architecture which good community support)
PIC12/14/16/18 (very ancient C unfriedly architecture, but cheap, broad 
choice of built-in peripherials, compilers are buyware)
PIC24 (very C friendly, has nothing to do with the 8 bit PICs, DSPIC 
familiy with extended DSP capabilities)
PIC32 (powerful MIPS core plus PIC24 peripherials)
ARM Cortex M1/M3 (core made by various manufacturers so it's easier to 
change to a different mfg, widespread support, good free 
compilers+debuggers; many many enhancements to the older ARM7 architecture)
TI MSP430 (well-known for energy efficiency, less peripherials than AVR 
or PIC)
8051 (ancient architecture, but still widespread, different mfgs)

-- 
Mit freundlichen Gr��en

Frank-Christian Kr�gel

On May 5, 8:01=A0am, FJG <f...@invalid.invalid> wrote:
> - USB memory stick to upload new settings, download reports

> weatherproofed - will operate outdoors, off 12V DC

Those two are in conflict.
Might be smarter to find a RF link to a USBkey+Netbook, or similar so
you can extract the data in a cordless way.

Something like this ?
https://www.silabs.com/products/wireless/wirelessmcu/Pages/Si1000SynapseWir=
elessModule.aspx

-jg

On Tue, 4 May 2010 20:01:36 +0000 (UTC), FJG <fjg@invalid.invalid>
wrote:

>The basics are 
>input - RFID tags, info probably read over RS-232
>output - solenoids / relays to turn a motor on
>I/O - USB memory stick to upload new settings, download reports
>control panel - three buttons and possibly a cheap LCD display
>optional - WiFi interface
>weatherproofed - will operate outdoors, off 12V DC

What is the environment temperature range ? 
You may have to select the components based on the temperature range. 

LCDs will not work well in a hot environment. 

You may have to derate the controller power consumption e.g. by
running it well below maximum frequency or reduce the output currents
for digital outputs etc. 

Weatherproofing will also make it harder to get rid off  the
dissipated heat, thus the box inside temperature can be much higher
than the environment temperature.

FJG wrote:
> I have a potential project coming up, where I may have 
> some influence on the hardware.  The spec is of necessity
> still slightly woolly, so my apologies for that in advance.
> 
> The basics are 
> input - RFID tags, info probably read over RS-232

I assume you mean you'll use an RFID reader that "talks EIA232"
to your "board"?  I.e., all you need is a UART (?)

> output - solenoids / relays to turn a motor on

Do you need these on the board?  Or, hammer drivers?  Or,
just a bunch of "digital outputs" that you will ultimately
interface to some OPTO-22's, etc.?

> I/O - USB memory stick to upload new settings, download reports

 From your description of the role of the tags, I assume your
settings only require a few KB, at most (e.g., 10 bytes per tag).
How big are these reports?  Do they have to be created in ASCII
(i.e., how will they be *read* "elsewhere"?  Could you put
a small application elsewhere to interpret raw data and
pretty-print it?)

> control panel - three buttons and possibly a cheap LCD display

What sort of display -- 7 segment, full graphic, color, etc.?

> optional - WiFi interface

What happens over the WiFi interface?  Can you use other
wireless protocols?  Range?  Data rate?

> weatherproofed - will operate outdoors, off 12V DC

Usually, weatherproofing happens in the *enclosure* choice.
However, if you have other environmental extremes that will
pertain to the board as a consequence of this, you will need
to identify/quantify them (e.g., what sort of ambient
temperature range *inside* the enclosure -- taking into
account power dissipated by the board, power supply, etc.)

> ROM / RAM / CPU requirements are going to be modest by today's
> standards.  We're talking about, say, 200 RFID tags to recognise,
> each of which has an individual setting for the amount of time
> to turn the relay / solenoid on for.

How big is the tag data?  Can you just store a hash of that
or do you need to store the actual tag itself?  I.e., are
you concerned with a "foreign" tag being interpreted as
one of your 200 "bonafide" tags?

Can the tag itself contain the "amount of time to turn the relay
on for", etc.?  Or, is it just a R/O tag that you treat as a
"unique identifier" used in an associative array paired with
the "on time data"?

> So any suggestions for a single board microcontroller that'd
> provide the above at reasonable cost, with the minimum of hassle,
> with a (preferably free) C toolchain?
> 
> Personally I think the idea of a USB port on an outdoor piece
> of equipment is a bit nuts, so any suggested alternatives?
> Bluetooth?

Depends on power requirements (range), etc.  From what
little you've said, I'd look at something like ZigBee as
your data rates are probably low and power consumption
would be a bigger issue.

Depending on what you plan on "talking to" over the wireless,
you could also conceivably remote the user interface,
data store, etc. on the other end of the wireless link
(e.g., build a "black box" that only has relays, RFID
reader and wireless as it's "I/O's" -- let everything else
be injected or displayed "remotely")

<shrug.  Hard to be more specific without specifics.