Sixteen SPI devices simultaneously - possible to bit-bang this with only digital I/O?

[bendrinksalotofcoffee]

Title basically says it all. I need to read 16 SPI devices simultaneously. The devices are AD7606B 8-channel AD converters. The way I see it, that's a total of 36 DIO, 32 inputs from the AD7606 array and 4 outputs to control them (CONVST, CS, SCLK, and RESET if you're following along in the data sheet). Is there any reason I can't do that with a USB-6509 or a PCIe-6509?

[santo_13]

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@bendrinksalotofcoffee wrote:

Title basically says it all. I need to read 16 SPI devices simultaneously. The devices are AD7606B 8-channel AD converters. The way I see it, that's a total of 36 DIO, 32 inputs from the AD7606 array and 4 outputs to control them (CONVST, CS, SCLK, and RESET if you're following along in the data sheet). Is there any reason I can't do that with a USB-6509 or a PCIe-6509?

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6509 supports only static DIO, which means the timing between level transitions is determined by software, which is something you don't want for timely capture of data from ADC.

[ZYOng]

Since the datasheet specifies that VDRIVE must be between 1.71 V and 3.6 V, NI-DAQmx device is out of the equation unless you want to add an external logic shifter.

The next option is PCIe-653x, which provides digital sampling clock of up to 50MHz but only comes with 32 DIO channels. There is an example for SPI Generation and Acquisition using HSDIO Hardware

The best option is NI R Series. Either USB 7845R OEM (48 DIO) or PCIe-7820 (128 DIO) supports clock rate of up to 80MHz. However, you need LabVIEW FPGA Module to program them.

[santo_13]

What is your goal? why these ADCs must be simultaneously sampled?

As ZYong advised, a cost-effective approach would be the RIO card to synchronously read data from 16 ADCs

[bendrinksalotofcoffee]

My goal is to sample sixteen eight-channel ADCs simultaneously. I’m reading 128 sensors at the same time. 

[santo_13]

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@bendrinksalotofcoffee wrote:

My goal is to sample sixteen eight-channel ADCs simultaneously. I’m reading 128 sensors at the same time. 

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What kind of sensors? and why are you implementing your own ADC based DAQ instead of getting a COTS DAQ?

Downside of implementing your own DAQ system is with the inability to calibrate and have a known measurement accuracy.

[ZYOng]

On top of what santo_13 asks, what's your sample rate requirement?