[chbot] The X-plane multiplex problem

[Mark Atherton]

OK, before you pile in, he is using I2C on a VGA port. Very cool idea.

-mark

On 16/05/2018 7:27 PM, Mark Atherton wrote:
>
> Synco,
>
> Still not sure how X-plane connects to the I2C devices - maybe a USB 
> to I2C bridge, or are you bringing the SMB bus directly off of the 
> motherboard ?
>
> -Mark
>
> -----------------
>
> Couple of our messages have been corrupted, here is Synco's earlier 
> reply to me
>
> -----------------
>
> Wed May 16 00:33:27 2018
>
> Hi Mark+,
> I've written a few plug-ins for X-Plane, rather than use the UDP 
> protocol, yet by next meeting that'll most likely have changed and 
> will be happy to share. If each panel was to be stand-alone, from all 
> the different I2C port expanders out there, it's likely you would have 
> spare I/O that would avoid multiplexing / scanning tricks. Also, if 
> you are running Linux, and don't want to use a Raspberry Pi, another 
> option is to use the I2C adapter on your monitor connector. I've done 
> this in the past, (and will again), yet be careful to ensure voltage 
> levels and device addresses don't conflict !
>
> For example here is what it looks like on my pc:
> $ sudo apt install i2c-tools
> $ i2cdetect -l
> i2c-3 unknown    NVIDIA i2c adapter 7 at 1:00.0  N/A
> i2c-1 unknown    NVIDIA i2c adapter 4 at 1:00.0  N/A
> i2c-4 unknown    NVIDIA i2c adapter 8 at 1:00.0  N/A
> i2c-2 unknown    NVIDIA i2c adapter 6 at 1:00.0  N/A
> i2c-0 unknown    NVIDIA i2c adapter 2 at 1:00.0  N/A
>
> $ sudo i2cdetect -y 0
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:          -- -- -- -- -- -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
>
> $ sudo i2cdetect -y 4
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:          -- -- -- -- -- -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- 37 -- -- 3a -- -- -- -- --
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: 50 51 52 53 54 55 56 57 -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
>
> And if you run out of addresses you can always add a i2c-i2c bridge: 
> https://www.aliexpress.com/item/TCA9543A-Low-Voltage-2-Channel-I2C-Bus-Switch-Interrupt-Logic-And-Reset-Module/32763291440.html
>
> /s
>
> On 15 May 2018 at 22:01, Mark Atherton <markaren1 at xtra.co.nz> wrote:
>
> > Hey Synco,
> >
> > Any chance of a quick tutorial how X-Plane processes incoming UDP 
> packets, and assigns associated bytes/bit-positions to each function.
> >
> > Getting some kind of spec. from Paul (or help write one) would be 
> very useful to determine cable loom lengths, number of inputs, types 
> etc. For each control: Push Button, On/Off, Rotary (number of 
> positions) ,or Potentiometer (and resolution), and max scan time.
> >
> > He may have been using a 4 position switch with 4 wires, when it may 
> actually be an encoded 2-bit problem. Not sure if full size, low cost 
> rotary binary outputs switches are readily available - hex coded 
> switches are obviously too small...  There was mention of an R-2R 
> ladder on the switch and an ADC - this seems a bit over the top (?). 
> How about using a 1 of 4 rotary switch, and a small diode matrix (4 
> diodes + 4 pull down resistors) to encode to binary - there are 
> obviously larger bit-savings with 8 and 10 positions switches.
> >
> > Not personally a fan of carrying I2C any great distance due to noise 
> immunity issues (or lack thereof), but screened twin cable (and 
> associated unwanted capacitance) with low clock rate (10kHz ?) and 
> careful grounding may be OK though.
> >
> > R-PI seems over the top to convert bits into UDP, but I guess they 
> are readily available, well supported, and low cost, so why the hell 
> not...
>
>
>
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