SSI USB

[ssk]

 Last week I stumbled across a posting that pointed towards a USB module that took SSI inputs. I can no longer find it! I think it was a fairly obscure product as it was only available in OEM version.

Does anybody know what it is!!?

Thanks

Simon

[Nick_CH]

Hello SSK,

I think, this module is the NI-USB-8451 I²C/SPI Interface. This module provide a SSI/I2C protocol.
information about SSI: link: What is Serial Synchronous Interface (SSI)?

Best regards,
Nick_CH

[ssk]

Thanks Nick,

I was looking for that for about an hour yesterday!!

Si

[ssk]

Can anybody tell me the difference between SSI and SPI?

Thanks

[Nick_CH]

Hello Scc,

The I2C protocole is a kind of SSI (Serial Synchronous Interface) where the data  uses only two bidirectional open-drain lines.
The SPI (Serial Peripheral Interface) is a synchronous serial data link standard that operates in full duplex.

More information about those protocole can be found on Wikipedia:
SPI Serial Peripheral Interface Bus
I2C Inter-Integrated Circuit

Best regards
Nick_CH

[ssk]

So could this USB module be used to read an SSI device?

Thanks

si

[Nick_CH]

Dear ssk,

Apologie, I just realize something, the SSI signal are differential voltage and the I2C are open-drain grounded.

That means you cannot directly connect them together.
The best think, I suggest you to study the sensor data (voltage level) and the I2C protocol (voltage level)

For example,
to connect the SCLK to Clock+ and Clock-, you can use a MAX 488 or similar
to connect the MISO to Data+  and Data- also.

Best regards,
Nick_CH

[Chris G in AE]

Not only can you not connect the two together, the 8541 driver does not support SSI.

You can find a definition for SSI here

SSI Bus {The Synchronous Serial Interface [SSI] bus consists of four signals; SCLK, SDATA, SDEN0, and SDEN1. SDATA is a bidirectional [three-state] data line which requires a pull-up or pull-down resistor. Data is sent in 8 bit bytes, LSB first. The SCLK signal is only active during transfers. Data is clocked out on the falling edge and clock in on the rising edge [of the Master]. The other two pins SDEN0 and SDEN1 are enable pins, active high.}

That means SSI uses only one data line , versus two for SPI. And they clock in on falling edge and clock out on rising edge. That is not supported with our 8451 driver.

[ssk]

I thought I would post my solution for anybody else wanting to interrogate SSI using LabVIEW.

I used a PCI SSI card from www.deva.co.uk (product link http://www.deva.co.uk/product/deva001ssipci.htm) , the cards come with example LabVIEW drivers.

We have been using the card for some time with great success. They are 3 channel devices and we have a linear encoder on one channel and a rotary encoder on the other.

ssk

[LEMC]

Hi,

We want to use LabView with 6 SSI 13-bit absolute encoders. Basec on the info from the the past messages, we're checking the PCI SSI card  from www.deva.co.uk but we still have two questions:

In the website of the manufacturer, they say that provide LabView libraries to 5.0 LabView version. Are those libraries compatible with LabView 8.0?

As we want to use 6 encoders, we need to PCI SSI cards. Have somebody use simultaneously two of those cards with LabView?

Thank you in advance for any help.

LEMC