Panda II and digital input interrupt capacity

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#1

I’m reviewing the Panda II for a project involving reading pulses from 8 devices.

I need to reliably count the pulses concurrently from these 8 sources at up to 250Hz each and somehow hand this information off to an external system every 10 seconds.

I’ve been researching similar uses but cannot find much info on capacity. Some people seem to say they can process digital input at 2kHz where others are saying they are having difficulty at much lower rates.

In terms of exporting the information, I only need to hand a delta for each of the 8 sources at 10 second intervals. Given that I’ll be using 8 DIO pins already, what is the most efficient method of interfacing the board with something else? There will be a number of these which will need to be ultimately connected to a network, so my current thinking is I2C one or more of these to a separate device that has Ethernet.

Can the Panda II handles these 8 sources at 2kHz total, and if so will I2C introduce much overhead or should I consider another method?

Many thanks in advance for your advice.

#2

If you use managed code I doubt that the Panda can handle that rate.

In the past I have done some analysis, and doing nothing in the interrupt
handler will allow a rate of around 1700 interrupts per second before
running out of memory, due to the event queue growth.

You should be able to handle that rate if you use RLP.

#3

Mike, thanks for the quick response.

Using a slightly different approach, could you estimate what I could expect (in terms of total interrupts per second capacity) from the Fez Hydra (and .NETMF), assuming I’m using some sort of basic IP socket based comms to query the board?

#4

Ideally you would use a tiny micro, like the one on pulse in out board or DL40. This will only do one thing, count pulses and send to hydra or any board as a count. There are other options if you know hardware design.

#5

Gus, thanks for that… I hadn’t seen that one before.

So that would handle the grunt work of counting for the 8 inputs (and could handle 250Hz for each?) and then I could just connect that to a Hydra or Panda and read the count delta every 10 seconds?

If I were to use a Hydra, how many of these modules could I connect? I count 10 X/Y connectors… could I feasibly connect 10 of these for 80 devices (at my expected usage level)?

#6

It is near unlimited

#7

Are there any detailed specs available on the Pulse InOut Module?

I’ve looked at http://www.ghielectronics.com/catalog/product/392 but could not find any reference to the max freq supported on the inputs.

I note it has a 50MHz processor, however I’m guessing I can’t just divide by 8?

#8

It is meant to measure pulses from a RC controller, a 1ms pulse every 20ms is typical.

What are you trying to do?

#9

I’m trying to read 8 inputs at up to 250Hz, however I’d like to understand what the upper capability is.

#10

I should reiterate that it’s 250Hz each… total 2KHz

#11

We can get more details but please start new thread. This topic is about panda I see.

#12

Done… http://www.tinyclr.com/forum/topic?id=9406

Thanks

#13

Gus, any luck with those specs? I’ve posted again with a different topic but the only constructive response I’ve received so far is that it’s even worse than the Panda II…

#14

Please keep the thread in one place so we can help you better.