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PostPosted: Wed Feb 20, 2013 4:37 pm 
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My first finger in air guess was 16 bytes per output for switching based on up to 8 dig. inputs with fairly simple switching logic (and,or,not) reduced down for analogue value and > or <. Not thought that hard about storage format. So 128 bytes per module x 16 modules = 2K bytes. I'm guessing a typical road car application will probably be about 7 or 8 modules so I would want to allow for 16.


I like the idea of SD card for allowing config without plugging a laptop into the system, but it will use 4 i/o which would mean no address setting via links or dipswitches. I also wouldn't like to be cartain an SD card wouldn't be zapped by a module failure so it would require a full set of SD cards to be carried along with a single PDM.

The design isn't done & dusted yet, I'm leaving it to last after the digi dash stuff.

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PostPosted: Wed Feb 20, 2013 5:01 pm 
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How about making the output connections via a 2 position jumper
Position 1 - pdm control
Position 2 - hardwired 12v

It would provide ultimate get home capability


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PostPosted: Wed Feb 20, 2013 6:24 pm 
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A 20A jumper link ? :lol: Seems you need a special tool to get the box open costing over 100 sheets which makes it a non-starter anyway.


Next thought for the day.
Would you expect to switch these things off with the ignition, if so we need a relay capable of a hundred or 2 amps (I have one in mind but not checked specs yet). Alternatively, we need a power down option to slow / stop the canbus and allow the processors to go to sleep.

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PostPosted: Wed Feb 20, 2013 7:11 pm 
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I was thinking more along the lines on 'nana plugs/sockets :lol:

Never thought about power down. I guess the elegant way is to put everything to sleep - CAN supports suspend and resume via the bus if the dspic implementation handles a wakeup from the bus
I'd guess something like a high priority go to sleep command gets issued from whicheverdm is hooked to the ignition switch
The other perhaps easier system would be to run a high power cable and a low power switched cable to run the electronics. In fact I would certainly lay the boards out to accommodate that with a jumper connection to power the processors off the high current supply


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PostPosted: Thu Feb 21, 2013 12:57 am 
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I had thought of that and was planning on making one of the 12V pins just for the logic (pins rated @ 10A so will probably run 5 or so in paralell)

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PostPosted: Thu Feb 21, 2013 2:20 pm 
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Better still perhaps
If you planned it so that the low power bus controlled a relay in the units you'd have the capacity to drive a virtually unlimited number - must say I struggle to see a box sucking 2A though
Possibly if you implement the provision for a diode wired "or" from say output 1 back to the relay too
That would give max flexibility I think
If you get bus induced sleep figured out leave the relay /diode out
Otherwise fit relays and either a switch powers the whole network or a single pdm can do so

It's a bit of a git when you think about it in a complete system context
The obvious thing would be to have the ACC position on the ignition switch power up the network. Sounds simple but you can't get in to the car to do that as the central locking is switched off :oops:

What the bimmer does is, i suspect, fire it up off the door and remote sensors. I know for sure that when you take the key out and lock it the car stays awake for 20 minutes. There's various references in the BMW diagnostic software to leaving the car for >20 minutes so the car goes to sleep and takes the new setting ..... Ahh, bless,poor thing is tired after all that programming probably :lol:

In this context it would be handy if every module could power up the network
In fact, thinking about it in those terms you can't switch the units off by turning off the power :( unless you designate that some key units stay awake but in low power state


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PostPosted: Thu Feb 21, 2013 2:54 pm 
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I can easily 'wake' all items on the bus by driving it to a 'dominant' state from any unit for a second, so Ideally put the 'unlock' and 'ignition' on the same box and let it keep an eye on those inputs. With the pic, it's easy to get it to sleep for 1/2 sec then wake for a few milliseconds to check inputs, requires very little power (we get over a year from a coin cell on some of our stuff).

Current draw for the logic is only a few milliamps so switch direct with the ignition switch.

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PostPosted: Thu Feb 21, 2013 3:06 pm 
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AH-HAAAAAAAAAAAAAAAAAAHHHHHHHHHHHH
Sorry, went a bit Alan Partridge there :lol:

Looking at the dspic30F4013 data sheet

Input Pins
Datasheet wrote:
7.3 Input Change Notification Module
The input change notification module provides the
dsPIC30F devices the ability to generate interrupt
requests to the processor, in response to a Change-Of-
State (COS) on selected input pins. This module is
capable of detecting input Change-Of-States, even in
Sleep mode, when the clocks are disabled. There are
up to 10 external signals (CN0 through CN9, CN17 and
CN18) that may be selected (enabled) for generating
an interrupt request on a Change-Of-State.


On CAN
Datasheet wrote:
17.3.2 DISABLE MODE
In Disable mode, the module does not transmit or
receive. The module has the ability to set the WAKIF bit
due to bus activity, however, any pending interrupts
remain and the error counters retain their value.
If the REQOP<2:0> bits (CiCTRL<10:8>) = 001, the
module enters the Module Disable mode. If the module is
active, the module waits for 11 recessive bits on the CAN
bus, detects that condition as an Idle bus, and then
accepts the module disable command. When the
OPMODE<2:0> bits (CiCTRL<7:5>) = 001, that
indicates whether the module successfully went into
Module Disable mode. The I/O pins revert to normal I/O
function when the module is in the Module Disable mode

If I read that right the can bus reverts to a simple input pin

Datasheet wrote:
20.7.1 SLEEP MODE
In Sleep mode, the clock to the CPU and peripherals is
shut down. If an on-chip oscillator is being used, it is
shut down.
The Fail-Safe Clock Monitor is not functional during
Sleep since there is no clock to monitor. However, the
LPRC clock remains active if WDT is operational during
Sleep.
The brown-out protection circuit and the Low-Voltage
Detect (LVD) circuit, if enabled, remains functional
during Sleep.
The processor wakes up from Sleep if at least one of
the following conditions has occurred:
• any interrupt that is individually enabled and
meets the required priority level


From that I infer that an input change can wake the device from low power clocks off sleep. It would also appear the CAN interface can do the same
I think that means that you configure selected inputs to wake the module (via the PC configuration program) - door switches etc - and a module can then wake the rest of the system up via the CAN bus. Job jobbed


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PostPosted: Thu Feb 21, 2013 3:27 pm 
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Correct. Provided I've got the can on an input that has interrupt on change facility, we don't need a 1/2 sec dominant state, it will wake on the first normal transmission. Worst case is set the watchdog timer to wake it every 1/2 sec, check the input then go back to sleep.

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PostPosted: Thu Feb 21, 2013 4:38 pm 
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The chip specific docs don't tell you squat
It mentions that the CAN has IDLE and sleep modes but makes no mention of what they are or what they can do

Assuming it's ECAN then pp66 Sect 21.12 of THIS suggests that ECAN can wake from either sleep or idle via the aptly named WAKIE setting. I've checked the specific chip doc and that setting is present so I believe a wakeup interrupt can be routed to the CAN interrupt which, if enabled, should wake the processor


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PostPosted: Thu Feb 21, 2013 4:42 pm 
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To be safe do you have an INT pin that could be freed up? :lol:


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PostPosted: Thu Feb 21, 2013 6:30 pm 
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I/O is somewhat short on the ground with all the power pins. No int needed, if needed I can switch can off to allow the pin to be read as an I/O pin. Hopefully it can do interrupt on change, if not I can poll it every 1/2 second in between sleeps, or I can switch to low speed internal osc. which only draws microamps and poll in a software loop which wakes early if needed.

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PostPosted: Mon Feb 25, 2013 5:50 pm 
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So to recap a typical system as an example (thanks for starting this Steve)

PDM 1 - Rear of car
IN 1 - Boot Open
IN 2 - Fuel Level (analog)
IN 3 - Fuel Warn (digital)
OUT 1 - Tail
OUT 2 - Brake
OUT 3 - Reverse
OUT 4 - Fog
OUT 5 - N/S Flash
OUT 6 - O/S Flash
OUT 7 - Rear heater.
OUT 8 - Rear wiper.

PDM 2 - Door NS
IN 1 - Window Up
IN 2 - Window Down
IN 3 - Lock
IN 4 - Unlock
OUT 1 - Window Up
OUT 2 - Window Down
OUT 3 - Lock
OUT 4 - Unlock
OUT 5 - Mirror Left
OUT 6 - Mirror Right
OUT 7 - Mirror Up
OUT 8 - Mirror Down

PDM 3 - Door OS1
IN 1 - OS Window Up
IN 2 - OS Window Down
IN 3 - NS Window Up
IN 4 - NS Window Down
IN 5 - Lock / unlock.
OUT 1 - Window Up
OUT 2 - Window Down
OUT 3 - Lock
OUT 4 - Unlock
OUT 5 - Mirror Left
OUT 6 - Mirror Right
OUT 7 - Mirror Up
OUT 8 - Mirror Down

PDM 4 - Door OS2
IN 1 - Mirror Up
IN 2 - Mirror Down
IN 3 - Mirror Left
IN 4 - Mirror Right
IN 5 - Mirror Select

PDM 5 - Dashboard 1
IN 1 - Turn Left
IN 2 - Turn Right
IN 3 - Hazzard
IN 4 - Side
IN 5 - Head
IN 6 - Main / flash
IN 7 - Fog
In 8 - Rear Fog
OUT 1 - Dash lights.
OUT 2 - Main Beam warning.
OUT 3 - Left Flasher warning
OUT 4 - Right Flasher warning
OUT 5 - Fog light warning.
OUT 6 - Low fuel warning.
OUT 7 - Cabin lights.

PDM 6 - Dashboard 2
In 1 - Wash
IN 2 - Wipe rear
IN 3 - Defrost
IN 4 - Brake
IN 5 - Door open LHS
IN 6 - Door open RHS

PDM7 - Front Of Car (can be combined with 6 if wanting to mount in cabin)
Out 1 - N/S Flash
Out 2 - O/S Flash
Out 3 - Side
out 4 - Head
Out 5 - Main
Out 6 - Fog lights.
Out 7 - Horn
Out 8 - Wash
IN 8 - Reverse

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PostPosted: Sat Mar 02, 2013 12:03 am 
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Following a very underwhelming response on the kitcar forum, I think it's time to shelve this. I really can't see a market.

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PostPosted: Sat Mar 02, 2013 12:58 am 
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Was that on lowcostbuilders?

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