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When I read about SSI communication I can see that a pair is used for clock and another pair is used for data transmission as follows:

enter image description here

On the other hand if I read about RS422 all lines are data and there is no clock:

enter image description here

I'm a bit confused about hardware standard and communication standard here. As far as I know the RS232 port of the PC is used for async serial communication but SSI is sync serial communication and the RS422 converter will only change voltage levels not the communication mode(it wont change sync to async).

Now if the data from an SSI sensor to be sent to a PC which has RS232 port, would an RS422 TO RS232 converter work? Or one needs another approach or interface?

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No, a simple electrical interface converter won't work here, as the protocols sent over the interfaces are incompatible.

RS-422 and RS-232 are specifications for electrical interfaces, they do not define what signals are sent over it.

PC sends asynchronous start-stop data using an UART. These signals are just sent at RS-232 levels.

SSI uses clock and data. These signals are just sent at RS-422 levels.

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  • \$\begingroup\$ So how can I make the protocols compatible? Should I look for for something like?: SSI sensor--->RS-422/485 converter-->Arduino Software serial(or similar uC board)--->USB--->PC ? \$\endgroup\$ – floppy380 Oct 18 at 11:41
  • \$\begingroup\$ Something like that if you want to build it yourself, but it depends on what the SSI sensor needs to work, but you did not mention what SSI device it is. Software serial is completely wrong approach as SSI is not asynchronous start stop signaling. Perhaps SPI can be used for SSI better, and leave the UART for PC communications. \$\endgroup\$ – Justme Oct 18 at 11:49
  • \$\begingroup\$ That's a datasheet for a whole bunch of sensors that can be ordered with all kinds of different output options, there's even two different versions of SSI protocol available. Impossible to determine from that. \$\endgroup\$ – Justme Oct 18 at 12:13
  • \$\begingroup\$ SSI output without parity the one which says "28/SI = SSI RS485 w/o parity". \$\endgroup\$ – floppy380 Oct 18 at 12:14
  • \$\begingroup\$ Still, that datasheet does not describe the protocol timings for that sensor. In general, there are application notes how to do SSI with SPI so it must work. At least the interface can be bit-banged manually. \$\endgroup\$ – Justme Oct 18 at 12:23

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