Communication FDCAN

Communication FDCAN#

There are two FDCAN communication connections, that have to be described. To control the PDS stack, one must connect to PDS_CTRL module, using 3-pin connector.

There are also 6-pin connectors available on PDS_PS module, that allow for connecting MD series motor controllers and other FDCAN devices. However:

Warning

PDS_CTRL FDCAN is not internally connected to PDS_PS modules. They are independent signal lines, that can be connected externally. To allow a single CANdle communicate with PDS and MD on a single string.

PDS_PS module connectors#

By default all connectors on PDS_PS module, have their CAN_H and CAN_L lines disconnected from each other, to provide only power though 6-pin connectors, allowing for up to 3 independent communication strings, to exist on the bus. There are however, bridge pads, located below 6-pin connectors to allow for connecting these buses together.

In order to connect using architecture please solder correct bridges underneath the Micro-Fit molex connector. These bridges connect CAN-L and CAN-H to another CAN-L/H of neighbor connector so the connection is transmitted without any adapters.

pds_power_stage_bridges — Fig. 9 FDCAN bridge placement#

Also control board has its own built-in CAN termination. If possible CAN termination should be placed on each ends of CAN circuit as shown below in recommended architecture examples.

Example 1#

In this example there are: CANdle, Control board, two Power Stage modules, six MD actuators (two per Micro-Fit molex connector) and CAN termination. In this example, termination on the CANdle is disabled.

Example 2#

In this example there are: CANdle, Control board, one Power Stage module and six MD actuators (two per Micro-Fit molex connector).This is the type of example that shows how to use all ports of single Power Stage without additional CAN termination. In this example, termination on CANdle is set to ON.

Communication Protocol#

Communication with a PDS device is done with the use of the “properties” concept. Each data or setting is a property of a module that forms a PDS device stack. Each property has its own underlying data type and access rights. Each property data occupies 4 bytes on the CAN frame. When communicating with the PDS, the host controller has to form a request frame that contains:

Message type ( which indicates what the host device is about to achieve ),
Type of the module that the message is addressed to,
Socket index where the particular module is connected,
Number of properties that it is going to read or write,
A set of properties (when reading) or a property/value pairs (when writing).

Note

As in all MAB CAN-based devices, the CAN ID is used to target specific devices. PSD is not an exception. When the frame is successfully received and processed by the PDS device, its response body depends on the message type.

When the host sends a write request to a module, the module responds with a frame containing the protocol status, the number of properties received, and a status code for each property. If some properties are read-only, they will return a status of ‘NO ACCESS’, while successfully written ones will return ‘OK’. To standardize communication, Control Board is considered as a module with a socket index 0. When the host sends a request to read properties the PDS device responds in similar fashion, the protocol status code, number of properties and a set of property status / value that corresponds to the properties set in the request.

Commands#

The message frame body depends on the command code that is always placed at the beginning of the frame. For simplicity, there are only two command codes supported by the PDS device:

Read properties from the PDS module Write properties to the PDS module

Command name	Command code [HEX]	Description
Read properties	0x20	Read properties from the PDS module
Write properties	0x21	Write properties to the PDS module

Properties#

Properties are the values representing some state or parameter of the module like temperature, voltage, CAN Baudrade, or module type connected to socket number 5. Obviously, not all properties are available on each module and also there are some common properties that each module must have.

NAME	ID	ACCESS RIGHTS	TYPE	DESCRIPTION	AVAILABILITY ON MODULES
NAME	ID	ACCESS RIGHTS	TYPE	DESCRIPTION	CB	PS	BR	IC
STATUS WORD	0x00	R	U32 - btiwise	A register were each bit represent different state of the module	✅	✅	✅	✅
STATUS CLEAR	0x01	W	U32 - bitwise	A register used to clear status bits in the STATUS WORD	✅	✅	✅	✅
ENABLE	0x02	RW	Boolean	Used to enable / disable particular module ( when write ) or simply check if it is enabled / disabled (when read )	✅	✅	✅	✅
TEMPERATURE	0x03	R	Float	Module temperature	✅	✅	✅	✅
TEMPERATURE LIMIT	0x04	RW	Float	Temperature limit. When module temperature exceeds this value it will become disabled and unable to be enabled back until cooldown	✅	✅	✅	✅
BUS VOLTAGE	0x05	R	U32	Power supply input bus voltage on control board / Power output voltage on power stage and Isolated converter	✅	✅	❌	✅
...	...	...	...	...	...	...	...	...
LOAD CURRENT	0x10	R	S32	Output current of the module	❌	✅	❌	✅
LOAD POWER	0x11	R	S32	Output power of the module	❌	✅	❌	✅
TOTAL DELIVERED ENERGY	0x12	R	U32	Total amount of energy ( in WH ) that was consumed by device connected to the module	❌	✅	❌	✅
TOTAL RECUPERATED ENERGY	0x13	R	U32	Total amount of energy ( in WH ) that was generated by the device connected to the module	❌	✅	❌	❌
...	...	...	...	...	...	...	...	...
CAN ID	0x20	RW	U16	CAN ID	✅	❌	❌	❌
CAN BAUDRATE	0x21	RW	ENUM*	CAN Baudrate ( 1M / 2M / 5M / 8M )	✅	❌	❌	❌
SOCKET 1 MODULE	0x22	R	ENUM*	The type of the module that is connected to socket number 1	✅	❌	❌	❌
SOCKET 2 MODULE	0x23	R	ENUM*	The type of the module that is connected to socket number 2	✅	❌	❌	❌
SOCKET 3 MODULE	0x24	R	ENUM*	The type of the module that is connected to socket number 3	✅	❌	❌	❌
SOCKET 4 MODULE	0x25	R	ENUM*	The type of the module that is connected to socket number 4	✅	❌	❌	❌
SOCKET 5 MODULE	0x26	R	ENUM*	The type of the module that is connected to socket number 5	✅	❌	❌	❌
SOCKET 6 MODULE	0x27	R	ENUM*	The type of the module that is connected to socket number 6	✅	❌	❌	❌
SHUTDOWN_TIME	0x28	RW	U32	The time ( in mS ) that PDS device waits before it turns off after receiving shutdown request (either from power button or from host device )	✅	❌	❌	❌
BATTERY_LEVEL_1	0x29	RW	U32	Levels ( in mV ) that defines ranges of battery energy available: 0 - L1 :: Almost discharged ( RED indication ), L1 - L2 :: Nominal charge ( YELLOW indication ), L2 < :: Fully charged ( GREEN indication )	✅	❌	❌	❌
BATTERY_LEVEL_2	0x2A	RW	U32		✅	❌	❌	❌
...	...	...	...	...	...	...	...	...
BR SOCKET INDEX	0x30	RW	ENUM*	Socket index of the brake resistor that we are going to bind with the power stage	❌	✅	❌	❌
BR TRIGGER VOLTAGE	0x31	RW	U32	The value of the power stage output voltage above which the brake resistor will be triggered (in mV)	❌	✅	❌	❌
...	...	...	...	...	...	...	...	...
OCD_LEVEL	0x40	RW	U32	The value of current ( in mA ) above which the module will enter OCD state if this value is exceeded for a time equal or grater than the "OCD Delay" time of the same module.	❌	✅	❌	✅
OCD_DELAY	0x41	RW	U32	The time ( in mS ) that the OCD level has to be exceedeed for to turn the module into OCD state	❌	✅	❌	✅
...	...	...	...	...	...	...	...	...
HW_VERSION	0xFD	R	ENUM*	Hardware version of the module	✅	✅	✅	✅
FW_VERSION	0xFE	R	U32 - bytewise	Firmware version of the Control board MCU	✅	❌	❌	❌
COMMAND	0xFF	W	ENUM*	Property used to send various commands to the PDS device like ( power off, reboot, etc... ).	✅	❌	❌	❌

Status and status clear words#

The terms ‘Status’ and ‘Status Clear’ indicate basic binary states or events within a module, such as whether it is enabled or a limit has been exceeded. The U32 bitwise type means that each bit in the value represents a different purpose rather than a singular numerical value. Like properties, status bits are module-specific—each module defines its own set, which may or may not align with those of othermodules.

NAME	BIT POSITION	DESCRIPTION	AVAILABILITY ON MODULES
NAME	BIT POSITION	DESCRIPTION	CB	PS	BR	IC
Enabled	0	Indicates whenever the module is enabled or not. Note that in case of Control board it indicates entire device power on status.	✅	✅	✅	✅
Over temperature	1	The temperature limit of the module has been exceeded	✅	✅	✅	✅
Over current	2	The current limit of the module has been exceeded (OCD state )	❌	✅	❌	✅
...	...	...	...	...	...	...
STO1	10	Safe Turn Off at input 1 has been triggered	✅	❌	❌	❌
STO2	11	Safe Turn Off at input 2 has been triggered	✅	❌	❌	❌
FDCAN Timeout	12	CAN message processing timeout	✅	❌	❌	❌
Submodule 1 error	13	Some error occurs on the module connected to the socket ( 1 - 6 ). Refer to the particular module status word for more details about the issue	✅	❌	❌	❌
Submodule 2 error	14		✅	❌	❌	❌
Submodule 3 error	15		✅	❌	❌	❌
Submodule 4 error	16		✅	❌	❌	❌
Submodule 5 error	17		✅	❌	❌	❌
Submodule 6 error	18		✅	❌	❌	❌
Charger detection	19	Indicates whenever charger has been connected to the device	✅	❌	❌	❌
Shutdown schedule	20	Indicates that the PDS device shutdown has been scheduled and the PDS device is about to be turned off within the time specified in the "Shutdown time" property of the control board.	✅	❌	❌	❌
...	...	...	...	...	...	...

Communication frames#

Generic frame body of the “Write property” ( 0x21 ) message:

nBytes	1	1	1	1	1	4	…	1	4	1	4
Frame field	Write property command code [0x21]	Module type	Socket index	Number of properties	Property 1 type	Property 1 value	Property 2 type	Property 2 value	...	Property N-1 type	Property N-1 value	Property N type	Property N value

Generic response to properties writes frame body:

nBytes	1	1	1	1	…	1	1
Frame field	STATUS	Number of properties	Property 1 Status	Property 2 Status	...	Property N-1 Status	Property N Status

Generic frame body of the “Read properties” ( 0x20 ) message:

nBytes	1	1	1	1	1	1	…	1	1
Frame field	Write property command code [0x20]	Module type	Socket index	Number of properties	Property 1 type	Property 2 type	...	Property N-1 type	Property N type

Generic response to properties read frame body:

nBytes	1	1	1	4	1	4	…	1	4	1	4
Frame field	STATUS	Number of properties	Property 1 Status	Property 1 value	Property 2 Status	Property 2 value	...	Property N-1 Status	Property N-1 value	Property N Status	Property N value

Response status codes#

Response to correct read or write request frames contains two different status code types. The overall message status code ( protocol status ) and per property status code ( property status ).

Overall message status codes:

Status	Code [ HEX ]	Description
OK	0x00	Request frame parsed correctly
Invalid message length	0x01	The received request frame length is incorrect. For example when the number of properties byte indicates 4 properties but only 3 types are provided. Or if the received frame length is less than the expected header.
Invalid module type	0x02	Module type code is out of range
Invalid socket index	0x03	Socket index code is out of range
No module at socket	0x04	There is no module connected to the desired socket index
Wrong module at the socket	0x05	The desired module type does not match the one actually connected to the desired socket

Properties status codes:

Status	Code [ HEX ]	Description
OK	0x00	Property read/write operation success
No property	0x01	The addressed module does not support the requested property
Invalid access rights	0x02	Requested read operation from write-only property or write operation to read-only property
Invalid data argument	0x03	Given data value during the write operation is invalid. For example when the user is trying to exceed some limit or pass some value that is out of valid enumeration range.