[Noisebridge-discuss] arduino dmx receiver

Phillip Pearson pp at myelin.nz
Fri Apr 1 01:27:14 UTC 2016


On Thu, Mar 31, 2016 at 5:07 PM, robb <sf99er at gmail.com> wrote:

> whaat!
>
> On Thu, Mar 31, 2016 at 3:40 PM, Phillip Pearson <pp at myelin.nz> wrote:
>
>> Thanks!  The boards are my own design -- an ISO3088 chip plus isolated
>> DC-DC converter
>>
>
> that's an
> Isolated 5-V Half-Duplex RS-485 Transceiver !!!!!!!!!!!!!!!!!!!!!!!!!!!
>
>> , and Neutrik connectors.
>>
>

Haha yes -- I got them as samples from TI.  I really wanted to be able to
isolate my circuit from the DMX ground.  Turns out that as I'm using an
ungrounded power brick, I probably don't need all of this, but I had all
the parts so I made them anyway :)



> I can confirm that the DMX code out there for Arduino and friends is a bit
>> flaky :)  As Mitch says, though, DMX code written for the Duemilanove
>> should work fine on an Uno, because it uses either GPIO or HardwareSerial;
>> the FTDI chip isn't required.
>>
>
> i can't seem to find "ISR(USARTn_RX_vect)" in HardwareSerial.cpp which is
> where i seem to need to start commenting out to allow the proper interupts
>


Take a look in HardwareSerial0.cpp; it looks like you'll want to search for
USART_RX_vect and USART0_RX_vect.  This probably changed when the Arduino
folks started making boards with more than one serial port.



>
>> I haven't tried receiving DMX on an Arduino, but I've implemented DMX
>> reception on a Freescale KE04 ARM chip, and it's not super hard.
>>
>
> maybe it's time to set down the avr chips & just use my rpi
>
>
>> The only tricky part is that the DMX packet starts with a 'break', where
>> the data line is held low for ~50 us (12.5 bit times).  This will show up
>> as a framing error, and is probably what you need to edit
>> hardwareserial.cpp for.
>>
>
> agreed
>
>
>>   I won't have time for a few days, but when I get these boards up and
>> running I'll see about hooking one to an Arduino and testing out some
>> receive code there.
>>
>
>  enjoy & that's music to my ears!
>
> I've been using a Teensy and a USB-DMX adapter (Chinese uDMX clone) on the
>> sending side so far.
>>
>> what are your inputs? pots, hardcoded modes, mic, multi-band eq,
> software...?
>
>

Nothing so far -- I'm making lighting stuff for my wedding in a couple of
months, and I want a friend who does a lot of DMX lighting to be able to
control my hardware with his controllers!

Cheers,
Phil
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