Using SSI encoder

SSI (Synchronous Serial Interface) is a digital protocol used by many encoder feedback device manufacturers. IONI Pro servo drive supports SSI encoders starting from firmware version 1.6.1.

SSI support details

As SSI is loosely defined standard, drive's SSI support may not cover all possible variations of the protocol. The following characteristics are supported:

• Read clock 1.5-2 MHz
• Strectched first clock for slower encoders
• Multiturn & singleturn readout
  • Multiturn resolution from 0-16 bits
  • Singleturn resolution 4-32 bits
  • Sum of MT+ST resolutions must be between 4 and 32 bits
• Binary and Gray code support

Current firmware version limitations:

• No absolute encoder information is utilized, motor still needs to do Phasing a.k.a. phase search and Homing to get absolute operation.

List of tested SSI encoders:

Manufacturer	Model	Notes	Test result
AMS	AS5311	12 bit magnetic encoders	All OK
RLS	Orbis	14 bits absolute	All OK
SICK	TTK70-AXA0-K02	24 bits absolute, gray code	All OK

Wiring SSI encoder

Wiring of SSI depends on the variant of SSI protocol present.

AMS SSI encoder chips

AMS SSI encoders are wired following way to IONI encoder connector:

AMS wire	IONI drive pin	IONICUBE D-Sub 15 pin number	Remarks
VSS (Ground)	GND	10
VDD5V (5V input)		9	Pin 9 is 5V supply output from IONICUBE to encoder
CLK	GPI3	11
CSn	GPI2	12
DO	GPI1	13

Refer to IONI & IONICUBE user guide for more info on wiring encoders.

Configuration

SSI parameters in Granity. Example settings for AMS AS5311.

To configure SSI, use Granity version 1.11.1 or later. Configuration steps:

1. Find out encoder MT and ST resolutions from encoder manufacturer's data sheet
2. Select Serial data encoder from Feedback deviceFBD
3. Select SSI type from Serial encoder typeFBS
4. Set number of MT and ST bits into parameters Single-turn bitsFBST and Multi-turn bitsFBMT. If MT not specified in encoder data sheet, set it zero.

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