SSI Protocol under STM32

[parisa]

Hello,

Here is the file of Encoder which uses SSI protocol for its communication. I have run this encoder with SPI and its interrupt in STM32 but I have some problems that I will be thankful if you could help me.

1) I want to know would it be possible to communicate with the Encoder with SPI thoroughly?

2) how can implant CRC-8 encryption for validate data

Thanks

[Tesla DeLorean]

The SSI6 mode looks viable

>>how can implant CRC-8 encryption for validate data

Provide a couple of example data patterns, make a reasonable donation, I'm sure I can provide a worked example of a software check routine.

The SPI peripheral may be able to implement it directly, you'd have to try.

[parisa]

I appreciate your help.

Here is some of the output ( each number is byte)

(MSB)000173->000096->000074->000045(LSB)

(MSB)000178->000224->000075->000204(LSB)

(MSB)000167->000224->000073->000163(LSB)

One of my questions is, By sending 4 bytes via SPI interrupt I can see the position of some bits is a little different. For example and based on the pdf file, When I change the distance of rotation surface the 23th bit should be 0 (As an error) but as you can see the second MSB byte changes from 01100000 to ‭00100000(22th bit)‬.

Thank you for your kindness

[Tesla DeLorean]

You might need to alter the clock phase settings for SPI peripheral. ie if data is latched on rising vs falling edges

A method of testing would be to bit-bang the interface, ie use GPIO to write and read bits via the pins.

[Tesla DeLorean]

Show the actual bit stream from the device, your presentation of the decimal numbers is not helpful.

The data is in SSI6 format, right?

[parisa]

Thank you so much for your comments.

Yes they are in SSI6 format. In the next days I will handle them by using the bit-bang method. I will tell you ASAP.

[parisa]

Dear Clive Two.Zero,

Here is some of my output (first data is between 0 to 65535(all data & 0xffff) and the second data is all received bits.

24434-3917569906

31180-3917576652

36042-2709621962

in this manner, the output of encoder works fine(0-65535) but the PV bit is on the 16th bit( n from 0 to 31).

[Tesla DeLorean]

Like to see the bits on the wire, not the interpretation of them

E9815F72 5F72 24434

E98179CC

A1818CCA

C0AFB9 -  44985 - 11101001100000010101111101110010

C0BCE6 -  48358 - 11101001100000010111100111001100

C0C665 -  50789 - 10100001100000011000110011001010

Looks like we're shifted off by one bit

[parisa]

Thank you so much for you comment, You are right. Before asking about CRC I have a big problem for losing my speed of MCU. I started a new topic on SPI which may help me to correct my MCU's speed.