Introduction

The Tamagawa receiver firmware running on PRU-ICSS provides a well-defined interface to execute the Tamagawa encoder communication protocol. The Tamagawa diagnostic application interacts with the Tamagawa receiver firmware interface.

Note: This implementation using Peripheral input/output mode of PRU-ICSS. Refer Peripheral IF mode for more details.

Features Supported

Supports full-absolute SmartAbs and SmartInc encoders compatible with Smartceiver AU5561N1
Supports all Data Readout, Reset and EEPROM commands
Baud rate: 2.5 MHz and 5 MHz
Support for concurrent multi-channel support on a single PRU
- Up to 3 identical encoders of the same frequency connected to all configured channels.
- Data transmission and reception must happen simultaneously on all channels.
- The encoder configuration and cable length should be the same on all channels.
- If encoders across channels don't respond at the same time, this mode will not work. Load share configuration should be used instead.
Support for multi-channel with load share mode (Refer Load Share Mode for more details).
- Up to 3 channels with encoders of the same frequency connected to all configured channels.
- Data transmission and reception can happen independently on all channels.
- After a command is sent, all channels wait for a response and process the response independently. However, all channels must finish processing before the next command can be triggered.
Support for 8x oversampling for RX
Note
In three channel interface of PRU-ICSS, receive (Rx) is oversampled at 8x of send (Tx). Therefore, the encoder interface frequency "f" should be such that Tx source clock value is divisible by "f" and Rx source clock value is divisible by "(8*f)".
Support for periodic trigger using PRU-ICSS IEP timer module with two modes:
- CMP Mode: IEP compare event based triggering (CMP0-CMP15)
- CAP Mode: IEP capture event based triggering (CAP0-CAP7) for external signal synchronization
Same clock frequency for all channels in multi channel mode within the same PRU-ICSS slice
- Different PRU slices can simultaneously handle encoders operating at different frequencies
Possible interface speeds with different source clock combinations

Clock Source
Interface Speed

PRU Core Clock (200 MHz)
2.5 MHz, 5 MHz

Features Not Supported

In general, peripherals or features not mentioned as part of "Features Supported" section are not supported, including the following:

Other baud rates.
Independent clock frequency for each channel in multi channel mode within the same PRU-ICSS slice
- Clock frequency is a PRU-ICSS slice level configuration
- Each channel within the same PRU-ICSS slice in multi-channel mode will have same clock frequencies

SysConfig Features

Note: It is strongly recommend to use SysConfig where it is available instead of using direct SW API calls. This will help simplify the SW application and also catch common mistakes early in the development cycle.

Attention: For each PRU-ICSS slice being used for Tamagawa, one module instance should be created in SysConfig. For up to 3 channels using 1 slice, only 1 instance needs to be added.

SysConfig can be used to configure the following:

Selecting the ICSSG instance (Tested on ICSSG0)
Selecting the ICSSG PRU slice (Tested on ICSSG0-PRU1)
Configuring PINMUX
Enabling SA Mux mode
IEP instance and IEP event selection for periodic trigger mode
Channel selection
Baud rate selection
Selecting RX and TX source clock
Booster Pack Support: Enable when using BP-AM2BLDCSERVO

Note: Tamagawa firmware is tested with ICSS Core Clock running at 200 MHz frequency.

Periodic Trigger Modes

The Tamagawa driver supports two types of periodic trigger modes for continuous position sampling:

CMP Mode (Compare Event Mode)

In CMP mode, the IEP timer compare event triggers position sampling. Compare events occur when the IEP timer counter matches the configured compare value. This mode enables fixed-rate periodic sampling.

Configuration:

Compare event range: CMP0-CMP15 (0-15)
Configured via tamagawa_config_periodic_trigger_cmp_mode() API
IEP compare event number set via tamagawa_config_iep_cmp_event() API
Event selection can be done in SysConfig
IEP configuration and CMP event configuration should be done in application. Driver uses above APIs to inform firmware to enable CMP periodic mode and uses the configured CMP event to start sampling periodically.

CAP Mode (Capture Event Mode)

In CAP mode, external signals trigger position sampling through IEP capture events. The capture event is triggered on the rising edge of the external input pulse, enabling event-driven position capture. Internal signals can also be mapped to IEP capture events via TIMESYNC/GPIOMUX router.

Configuration:

Capture event range: CAP0-CAP7 (0-7)
Configured via tamagawa_config_periodic_trigger_cap_mode() API
IEP capture event number set via tamagawa_config_iep_cap_event() API
Event selection can be done in SysConfig
IEP configuration and CAP event configuration should be done in application. Driver uses above APIs to inform firmware to enable CAP periodic mode and uses the configured CAP event to start sampling periodically.

Note

External signal must be routed to IEP capture input (if needed) in application
CAP6 and CAP7 support falling edge detection as well. In Tamagawa, rising edge is used always.

Attention: Both IEP event configuration APIs (tamagawa_config_iep_cmp_event() and tamagawa_config_iep_cap_event()) are automatically called during tamagawa_init() with values configured in SysConfig.

PRU-ICSS Resource Usage

Utilizes the Peripheral IF mode (3-channel peripheral interface mode) for Tamagawa communication. Maximum of 3 channels are available per PRU slice. (Refer Peripheral IF mode for more details)
Each channel has 4 pins (Clock, Data out, Data in, Output enable)
Following table contains details of memory usage, IEP usage and interrupt controller usage:

Attention: In addition to the following resources used by PRU firmware, SDK examples also configure IEPx CMP0 for IEP counter reset in periodic trigger CMP mode and IEPx CMP1 for generating SYNC OUT0 used as input to CAP in periodic trigger CAP mode.

Configuration per slice	PRU Core(s)	Memory Usage	IEP Usage	Interrupt Controller (INTC) Usage	Description
Single channel	PRUx	DMEM: 240 Bytes (0x00 to 0xEF) IMEM: ~ 1.6 kB	CMP Mode: IEPx CMPy for trigger (IEPx and CMPy selected in SysConfig) CAP Mode: IEPx CAPy for trigger (IEPx and CAPy selected in SysConfig)	INTC event/input number 18 or 21 (prx_pru_mst_intr[2/5]_intr_req) is used to trigger interrupt to Arm® Cortex®-R5F based on slice	IEP, CMP/CAP events and INTC signal are used only in periodic trigger modes
Multi-channel with single PRU core	PRUx	DMEM: 240 Bytes (0x00 to 0xEF) IMEM: ~ 1.28 kB	CMP Mode: IEPx CMPy for trigger (IEPx and CMPy selected in SysConfig) CAP Mode: IEPx CAPy for trigger (IEPx and CAPy selected in SysConfig)	INTC event/input number 18 or 21 (prx_pru_mst_intr[2/5]_intr_req) is used to trigger interrupt to R5F based on slice	IEP, CMP/CAP events and INTC signal are used only in periodic trigger modes
Multi-channel with load share across 3 PRU cores	PRUx	DMEM: 240 Bytes (0x00 to 0xEF) IMEM (per core): ~ 1.68 kB	CMP Mode: IEPx CMPy for trigger per channel (IEPx and CMPy selected in SysConfig) CAP Mode: IEPx CAPy for trigger per channel (IEPx and CAPy selected in SysConfig)	INTC events/inputs number 18, 19, 20 or 21, 22, 23 (prx_pru_mst_intr[2/3/4/5/6/7]_intr_req) are used to trigger interrupts to R5F based on slice	IEP, CMP/CAP events and INTC signals are used only in periodic trigger modes
	RTU_PRUx
	TX_PRUx

Note: For pin usage, see Pin Multiplexing section.

Tamagawa Design

Tamagawa Protocol Design explains the design in detail.

Example

Tamagawa Diagnostic

API

APIs for Tamagawa Encoder

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