RE: Re: Serial protocol questions

["Neil Wrightson" <neilw@xxxxxxxxxx>]

Hi Lehane,

1) I made reference to the compiler I use purely because it is a good
compiler. Each different type of slave could be a completely different
micro
and language - assembler, C, Basic Pascal etc etc. The main thing is that
handles its own task and interfaces to the required 485 network protocol.

2) Presumably the host software will do the device/instance id->node
number conversion and the device/instance config? - Don't know what this is
yet ???

3) "Mmm!
I'd caution against making the devices too complex. Better have 10
types (smaller/cheaper) than 1 do-everything and they are likely to
see the light of day faster. You can always put two/three/four in one
box." - Exactly


4) "So I'd go for:
1 n-way DC input (maybe analogue) variations can include on/off,
momentary, dimmer action, etc.
2 n-way DC output (maybe PWM on some for LED's) variations - opto,
SSR, etc
3 LCD display driver
4 RFID (...and RFID to me is EPC/ISO 18000)
5 Universal IR (UIRT on 485)
6 Dallas touch and/or one wire sensors
7 MSR (Track 1/2/3)
8 Bar Code Reader (UPC/EAN/ITF/Code 39)
9 Analog input/output (0-5/10V)
10 .... "

A) I was thinking of analogue inputs for switches etc, adds additional
security to remote switches I.e. window reed switches or PIR's

B) What is "EPC/ISO 18000"

C) What is MSR (Track 1/2/3)



5) "Agree on the power to the unit, although 12-15V maybe sufficient
as
the power consumption is going to be pretty low on most.
Not sure about the audio..I think that belongs on Ethernet in the
digital domain. I guess you're looking at voice/audio feedback but
would you want output from every device? Or would you command each
amp on? "
RS485 Cabling is generally as per the old coax 10base2, one long line with
terminators on either end.
With up to 32 devices on this line, that means 64 connections, each with
it's own voltage drop. The higher you can have the supply voltage the less
current in the supply lines the less voltage drop on the cable and the less
impact of voltage drops on the network connectors.
A lot of filed devices requires 12VDC so you would at least have to add 50%
i.e. 18VDC for the interconnecting power supply. I know of lots of off the
shelf 24VDC supplies out there. But, I think that as long as we design the
system so that it can handle from 12..24VDC, we can leave it up to the
individual.

6) As far as the audio goes, my intention was that we use the speaker out
of
the HA pc. Nothing fancy.
I see this as been a separate plug in add on board to the main slave
terminal with a small amp etc.


7) RS485 Comms Speed
For each slave the master must Tx a message and then Rx a message. 32
Slaves
times * 2 * Packet size of say ten characters = 640 bytes. At 9600 baud
this
would mean dial around would take 1.5 seconds. In reality this would be
somewhat longer with internal delays etc. Hence the reason that I suggested
38400 baud. I know basic chips may have issues with this. Again perhaps
user
definable 9600/38400.
Build the network to your own needs.


Neil.





written in a completely differant language or


Regards,

Neil Wrightson.
-----Original Message-----
From: g8kmh [mailto:lehane@xxxxxxx]
Sent: Tuesday, 25 January 2005 12:46 AM
To: ukha_xpl@xxxxxxx
Subject: [ukha_xpl] Re: Serial protocol questions




I've dropped my response in below.

Lehane

--- In ukha_xpl@xxxxxxx, "Neil Wrightson" <neilw@n...>
wrote:
> Hi Guys,
>
> 1) I'm all for a combined project.
>
> 2) I don't want to start another mine is better than yours
discussion, but,
> I use AVR's :) I have a great compiler AVRCo with true multitasking
etc

To some extent it is irrelevent to most end-users. Few are going to
change code, some will want prog'ed devices and most a kit (or at
least PCB and CPU).

The protocol outline is doable across a wide range of devices, indeed
it needs to be interoperable.

>
> 3) I think that a dedicated 485 network controller will be
required. I think
> the 485 comms will probably run about 38400 baud.
>     A 16MHz AVR will happily look after this.
>     The network controller will pass and receive all state changes
to the PC
> as well as heart beats for each device.
>     Comms to the PC could be 9600.
>

A separate controller has some advantages of redundancy and
interfacing with Win* or *nix.

With xPL not on the wire then heartbeats can be different internally
to externally.

Presumably the host software will do the device/instance id->node
number conversion and the device/instance config?


> 4) I envisage that there be at least two types of room controllers
(Perhaps
> we should start by settling on some names for these things)
>     a) Bedroom/kitchen/Living area Controller wish list
>         Display,
>         Personnel Switches for lights, sound muting etc,
>         Data entry method, Set room alarm clock time etc Sleep time
for
> lighting etc
>         IR Transmitter, Turn telly off when I fall asleep in bed,
turn
> ceiling fan off etc etc
>         Personal ID method
>         Sound
>         Movement sensor interface
>         Switch inputs for door & window reed switches
>
>     b) Basic room as in garage/toilet/bathroom wish list
>         Personnel Switches for lights etc,
>         Sound
>         Movement sensor interface
>         Switch inputs for door & window reed switches
>         Note - This is to be a cheaper version, no display only
beeper for
> sound alerts, maybe a IR receiver for configuration ??
>
> Hardware Solutions for above
>         Display,
> 16*2 LCD with LED backlight OR maybe a small graphic LCD, could
display
> small icons for
>
> you have email, voice messages, phone callers etc.
>         Personnel Switches for lights
etc,                             2..4
> Tactile switches I.e. small PCB mount
>         Light Control
> either 240V relay or triac, triac allows dimming, great for those
wee stops
> in the night
>         Data entry method,
> Universal TV remote. I can currently decode Sony or RC5 signals
>         IR Transmitter
> IR led on controller as well as capability to add an external IR
led else
> where in the room
>
> for better coverage if needed, I.e. Living room with external LED
for Stereo
> etc.
>         Personal ID method
> Dallas 1 wire ibutton, A lot cheaper & smaller than RFID!
>         Sound
> 2 Types, 1) Standard beeper. 2) Optional 1W speaker with sound
relaying from
> controller Pc
>
> Probably a separate optional PCB.
>         Movement sensor
interface                                    As
> suggested either a integrated unit actually on the controller or a
separate
> security PIR
>         Switch inputs for door & window reed switches
Standard style
> of inputs on a micro 5..12V tolerant.
>
>         Power Supply and Signal
>             I suggest that we use CAT5
>             Power - 2 Pairs 1 pair for 0V and one pair for +24V.
>             Comms Signal  - 1 Pair
>             Audio from PC - 1 Pair
>             If we try to use the standard pin outs for power over
Ethernet
> and data signals, nothing will be damaged if
>             a wrong device is plugged in somewhere.
>             Although, I did see these devices as being panel
mounted on the
> walls.
>
Mmm!
I'd caution against making the devices too complex. Better have 10
types (smaller/cheaper) than 1 do-everything and they are likely to
see the light of day faster. You can always put two/three/four in one
box.
So I'd go for:
1 n-way DC input (maybe analog) variations can include on/off,
momentary, dimmer action, etc.
2 n-way DC output (maybe PWM on some for LED's) variations - opto,
SSR, etc
3 LCD display driver
4 RFID (...and RFID to me is EPC/ISO 18000)
5 Universal IR (UIRT on 485)
6 Dallas touch and/or one wire sensors
7 MSR (Track 1/2/3)
8 Bar Code Reader (UPC/EAN/ITF/Code 39)
9 Analog input/output (0-5/10V)
10 ....

Agree on the power to the unit, although 12-15V maybe sufficient as
the power consumption is going to be pretty low on most.
Not sure about the audio..I think that belongs on Ethernet in the
digital domain. I guess you're looking at voice/audio feedback but
would you want output from every device? Or would you command each
amp on?








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