[Tfug] OT: Arduino group?

[Choprboy]

On Thursday 06 August 2009 17:11, Bexley Hall wrote:
[snip]
> PICs are *ancient* devices that started off as (jokes?) in
[snip]
> The big win for Microchip was giving away development tools for
> these devices (the devices themselves are rather inexpensive as
> well). 
[snip]
> AVR makes a better (? subjective) type of PIC-class machine
> but plays to the same "low end" market.  Note that both vendors
> offer a variety of products so not all of them are "crippled".

Well, yes PICs are old technology, but they are still evolving. Without the 
benefit of having actually sat down and had my hands on stuff yet... PICs 
seem to have several advantages. One, you can get PICs with a multitude of 
interfaces built in, including USB, CAN, dedicated serial, and ethernet. The 
AVRs only seem to come with USB. Two, It seems like you can get PICs with as 
little as 512bytes of memory to as much as several megabytes. The AVRs all 
seem to be in the couple of KB range. Third, as you said, Microchip has a 
wealth of free tools and comm code for building projects. The wide range of 
subsets/supersets in programming the PICs (everything from 8pin to 40pin) 
seemed a bit daunting though. AVRs seemed more consistent across the board 
for programming.

I looked around for a while at different devel boards and chips. One thing I 
want to do here shortly is build a network controlled I/O / sensing platform. 
Something to read voltage, I/O, temprature, etc. and be remotely readable by 
both HTTP and SNMP. Going the AVR route, I can get an Arduino for $40 plus a 
network shield for $50 more... A PIC w/ethernet devel board is $45. A PIC 
chip with built in ethernet MAC (sans mag/jack) was in the neighborhood of $7 
from what I remember searching. A comparable AVR chip was something like $4 
plus another $5 for an EN82J60...

So I would really like to hear from someone with build experience in both to 
find out the advantage/disadvantages of each in practice. The easy 
availability of Microchip libraries felt like a big advantage to me. But... 
things that made me wonder. Does having the larger memory space really help 
or does it just tend to get sucked up by a platform's less-efficient 
language? For a networked application being pinged and polled several times a 
minute, does having interrupt processing really help responsiveness, or is a 
continuous polling of the MAC sufficient? Are there big pitfalls in one vs 
the other? I suppose these all kind of come down to, you just have to build 
it and try both. Without practical experience, its hard to know where to jump 
in first.

> Unless I am missing an overload on the PLC term, a PLC is a different
> beast entirely.

Yep... I meant PLCs. I have a couple projects that need relay/timer logic. 
Things like controlling AC compressors and cooling towers or power 
monitor/generator start/stop controls.  The hardest thing I have found here 
is the availability of ethernet connections (for monitoring state), 
everything seems to want to be Modbus or CAN, and price. You can get a PLC 
with ethernet/SNMP. but it will cost you $3000. Not exactly experimentation 
prices. Im looking at a couple PLCs right now with 20 I/Os in ~$150-200 
range. Modbus, no ethernet though.


> Field Programmable Gate Arrays are dedicated pieces of "logic"
> that the user "customizes".  

Yep again... Like the above, I have a number of projects Id love to learn and 
dig into. Learning to use DSPs to process analog signals or encode data. In 
particular, Id like to build/find a reconfigurable general-purpose CPU on a 
PCI board. And a multi-input multi-monitor processing front end (think 
multi-source input KVM that does PiP/PbP to multiple monitors). Sigh.. If 
only I had time to play.


Adrian