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How Many AD2's on USB bus per PC


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If I have a USB network hub with 10 or more ports, how many Analog Discovery 2's could I connect?  Would I open up 1 Waveforms2015 window to control all of them, and would the all initiate with increasing device number?  I am asking out of interest on whether I could make a N-channel receive array with these devices.  When I acquire data in multiple scope acquisitions, at what point does the USB bus get used.  For N channels, is data stored locally on each device (for repeat) and only when I use a script to save the data is it transported over the USB bus?  I could imagine sequentially saving data from N devices if so versus a worst case of N devices competing for the USB data bandwidth.

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Hi @greig

The USB standard allows connecting up to 127 devices (including hubs) to an USB host. You should also make sure to have suffice power for supplying the devices, ~2.5W/dev
The WaveForms application can control one device at a time. For each device you should open a separate application instance.
Custom applications/scripts can control multiple device at the same time.
The acquisition of devices can be synchronized using the trigger IOs. These can acquire simultaneously in the device buffer.
The devices will share the USB bandwidth. This will be noticeable in case you want data streaming, reducing the 1-2MHz rate with one device to 100-200kHz with 10 devices.

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I have a similar interest/situation with other related posts

This post raised the questions for me

1) What is  the potential lag time for the acquisition start on each device?

I don't see any way to apply a time stamp or a signal marker to be able to exactly match the data timing from device to device .

Could be a problem in data correlation

2) One master device to run the overall script on but;

Slaves  would each  have to have their data acquisition parameters set in an individual Waveforms instance?

Requires  resetting  every time the devices are turned on?

Meaning you couldn't change slave device parameters from the master script during script run?

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Other option for multiple record channels would be

  1. Use NI Labview , either from institutional license or buy Labview Home edition from Digilent  It will scan for and  recognize multiple devices and has AD2 interface.Very steep leanring curve for me however
  2. Use NI Labview , AD2 for any drive /excitation functions and get used NI multiple channel DAQ PC card and breakout box. I currently have a setup like this that I have started the programming for but have not actually run.( Stuck on the drive /excitation circuitry problem) . Labview does recognize the DAQ card and the AD2 and process charting with them together ( NI PCI-6040E (Legacy) 16 Ch, 500 kS/s (1 Ch), 250 kS/s, 12-Bit, 2 AO, 8 DIO, 2 Ctr , SBC breakout box and cable )  Pricing on used  NI is all over the place( and negotiable ) all depends on the data rate you need. I am likely to have to have a three way system  AD2 for drive excitation, NI DAQ for slow equipment parameter  recording, several AD2 for faster test sample response data acquisition.

Please post followup if you do enable a  multiple AD2 setup.

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