Absolute Encoder Questions / SSI via 5i25

Here are 7i76 and 7i77 configs with SSI interfaces on the sserial expansion ports
Note that the SSI firmware is subject to change, especially in regards to how a cycle is started
suggested method is to set the pstart bit in each instance and use the global start register to start multiple channels
The data written to the global start register should be a bitmask of channels to start (its dont care currently but this will change)

A complete SSI interface should have the ability to set the bit size and start and end bits for counts per turn and
turn counts fields. In addition it should have the ability to extract the data twice and verify that the data repeats
(this is done by the rather inefficient method of setting the data transfer size twice as large as needed, in this case the SSI encoder repeats its output data) a gray/bin option is needed as well

I flashed the 5i25 with 7i76x2_ssi.bit and it went OK
Then I cut a config



When it starts I use Show HAL Configuration. There are raw pins. First I entered commands to test window but then I made a script



Nothing happens. 0x6800 remains 0xFFFFFFFF. I use O-scope for TX on 7i76 and no signal at all (though it switches once when setting DDR).
What is wrong?

Did you cycle the computer power after flashing the 5I25?
If not, you are still using the old firmware

Now I tried again, after several hours of power-off. Still nothing. I even verified the firmware against the bitfile.

My guess is I could be setting wrong SSI register. Is it supposed to be register 0 channel 0?
New regmap has channels, how are they supposed to work? A few devices on one port possible?

PCW wrote:

freeby.mesanet.com/7i77_ssi_7i74.bit

Has just one SSI interface on the 7I77s RS422/485 expansion port
Note that this expansion port is a RS-485 capable interface so has a /XMIT
enable on GPIO-0 you will need to set low by making GPIO-0 an output and setp-ing it low
in your hal file

I did not try this firmware. But with 7i76x2_ssi.bit TX state actually changes when I set GPIO12. Is it meant this way?

Looks like I zipped up the wrong bitfiles, I will make a new zipfile when I get to work in a few hours, sorry

Sure, no problem. Thanks for your help!

These should be the correct bit files:

freeby.mesanet.com/ssi2.zip

(for some reason the forum doesn't like attachments anymore)

Edit:I take that back it takes them but does not show that it did in the edit window, sigh...

That works, I have a response from the encoder!

I might note that if you have the clock polarity wrong the encoder will not work, but if you get the data polarity wrong
the encoder will work but the gray to binary converter will output gibberish.

With my Siemens SSI encoder the wiring is:

TX+ --> /CLOCK
TX- --> CLOCK
RX+ --> /DATA
RX- --> DATA

I will probably change the default polarities (reverse both)
so this is more natural when I finalize the SSI firmware.