[sdiy] wireless patching

[Roman Sowa]

Creating PWM from CV is pretty easy, I haven't thought it requires 
explaining. Simply sawtooth oscillator and comparator.

But you're right about the latency in RC world, I was typing faster than 
thinking. RC devices have low update rate considering modular use. After 
a quick check I see the fastest models have 11ms latency, and they are 
all pure digital anyway.

Roman


W dniu 2017-05-26 o 09:31, rsdio at audiobanshee.com pisze:
> My point is that the original question did not assume PWM already
> existed, or even digital.
>
> The original question concerned wireless modular linking of analog
> CV. Quincas asked whether a uP and ADC were necessary, or if there
> was a simple analog way to do it. I don't know of a simple way to
> create a PWM signal from an analog voltage (although I'm not assuming
> it doesn't exist just because I don't know about it :-)
>
> It could be more trouble to create PWM so that you can use RC, rather
> than simply use FM via some other method.
>
> The latency that you complain about in a digital word protocol would
> not necessarily be worse than the 50 Hz update rate of the RC
> solution. That's a 20 millisecond latency right there for the RC
> method. In that length of time, a 100 kbps digital protocol could
> transfer 2,000 bits, which is more than enough bandwidth for 8
> channels of 16-bit words. I'm thinking that a digital protocol would
> actually be lower latency than RC updates.
>
> Another issue is that the RC solution is limited to a 50 Hz sample
> rate, whereas the digital word protocol could manage a higher sample
> rate - maybe even 16 times the sample rate. Fortunately, the RC
> solution does seem to sample all channels at 50 Hz, but that's a
> fairly low limit.
>
> Brian
>
>
> On May 25, 2017, at 11:43 PM, Roman Sowa <modular at go2.pl> wrote:
>> PWM is digital output, so what's your point? Using digital words
>> over this radio module would require much higher bandwidth, they
>> usually are limited to 100kbps, sometimes much less. Higher
>> bandwidth models don't have keying input but take SPI or I2C,
>> packetize it and send embeded in some protocol, sometimes with
>> 2-way link. That creates latency.
>>
>> As Matthias just said, this is what RC control uses, TDM-ed
>> multiple PW. This is the best solution I think. One visit in RC
>> store and your wireless connectivity project finished, just add
>> filters to servo outputs of the receiver, as their output is PWM.
>>
>> Roman
>>
>> W dniu 2017-05-25 o 22:52, rsdio at audiobanshee.com pisze:
>>> FSK and ASK both assume digital input. If you want to send
>>> analog data, then you should be able to use standard FM, which
>>> can transmit analog signals. So long as the pilot frequency and
>>> the signal frequency survive the transmission, you should be able
>>> to reconstruct the analog signal on the receiving end.
>>>
>>> I do think that multiple CV would require multiple transmit
>>> frequencies and multiple receivers, though, to keep the signals
>>> distinct. That would be true with ASK/FSK or straight FM.
>>>
>>> Brian Willoughby Sound Consulting
>>>
>>>
>>> On May 25, 2017, at 2:29 AM, Roman Sowa <modular at go2.pl> wrote:
>>>> BT is no good for realtime. How about really simple $2 RF
>>>> modules that have FSK or ASK input? Not sure if you can freely
>>>> modulate with any PWM signal or is it quantized to some fixed
>>>> data rate, but common sense tells me that the simples cheapest
>>>> module just drive the radio directly. So you have wireless PWM
>>>> link, and that's just one step from CV.
>>>>
>>>> Roman
>>>>
>>>> W dniu 2017-05-25 o 01:13, Quincas Moreira pisze:
>>>>> Hey friends! If you were to design a fast and precise
>>>>> wireless transmission and reception system for eurorack, how
>>>>> would you doi it? Synth 1 > ADC > uP
>>>>>> Bluetooth > uP > DAC > synth 2 ?  Or is there a simple
>>>>>> analog way to
>>>>> do it with RF?
>>>>>
>>>>> I mainly want to send control signals, but as we know, those
>>>>> can be up in the audio frequencies or higher!
>>>>>
>>>>> The idea is to have like, 4 systems set up on 4 corners of a
>>>>> room and inter-patch them without stretching long cables all
>>>>> over the place. I think 8 sends and 8 receives on each remote
>>>>> patch box would suffice, and some system to match sends to
>>>>> receives.
>
>
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