Difference between revisions of "CAN Protocol"

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====Command Identifiers====
 
====Command Identifiers====
  
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TABLE GOES HERE
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{|style=" border-collapse: separate; border-spacing: 15; border-width: 2px; border-style: solid; border-color: #CCCCCC; padding: 0px; text-align: left; width: 800px"
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| style="padding: 3px 5px 2px 5px; background: #F0F0F0" | Variable Name
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| style="padding: 3px 5px 2px 5px; background: #F0F0F0" | Value
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| style="padding: 3px 5px 2px 5px; background: #F0F0F0" | Description
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| style="padding: 3px 5px 2px 5px; background: #F0F0F0" | Source
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| style="padding: 3px 5px 2px 5px; background: #F0F0F0" | Destination
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_SYSTEM_ON
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| style="padding: 2px 5px 2px 5px; | 0x01
 +
| style="padding: 2px 5px 2px 5px; | Start periodic communication
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_SYSTEM_OFF
 +
| style="padding: 2px 5px 2px 5px; | 0x02
 +
| style="padding: 2px 5px 2px 5px; | Stop periodic communication
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_PERIOD
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| style="padding: 2px 5px 2px 5px; | 0x03
 +
| style="padding: 2px 5px 2px 5px; | Set communication frequency
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_MODE_JOINT
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| style="padding: 2px 5px 2px 5px; | 0x04
 +
| style="padding: 2px 5px 2px 5px; | Command Transmission Mode
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_MODE_TASK
 +
| style="padding: 2px 5px 2px 5px; | 0x05
 +
| style="padding: 2px 5px 2px 5px; | Command Transmission Mode
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_TORQUE_1
 +
| style="padding: 2px 5px 2px 5px; | 0x06
 +
| style="padding: 2px 5px 2px 5px; | Index finger (1) torque command
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_TORQUE_2
 +
| style="padding: 2px 5px 2px 5px; | 0x07
 +
| style="padding: 2px 5px 2px 5px; | Middle finger (2) toque command
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_TORQUE_3
 +
| style="padding: 2px 5px 2px 5px; | 0x08
 +
| style="padding: 2px 5px 2px 5px; | Pinky finger (3) torque command
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_TORQUE_4
 +
| style="padding: 2px 5px 2px 5px; | 0x09
 +
| style="padding: 2px 5px 2px 5px; | Thumb torque command
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_POSITION_1
 +
| style="padding: 2px 5px 2px 5px; | 0x0a
 +
| style="padding: 2px 5px 2px 5px; | (unused)
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_POSITION_2
 +
| style="padding: 2px 5px 2px 5px; | 0x0b
 +
| style="padding: 2px 5px 2px 5px; | (unused)
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_POSITION_3
 +
| style="padding: 2px 5px 2px 5px; | 0x0c
 +
| style="padding: 2px 5px 2px 5px; | (unused)
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_SET_POSITION_4
 +
| style="padding: 2px 5px 2px 5px; | 0x0d
 +
| style="padding: 2px 5px 2px 5px; | (unused)
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_QUERY_STATE_DATA
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| style="padding: 2px 5px 2px 5px; | 0x0e
 +
| style="padding: 2px 5px 2px 5px; | Request joint state
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
| style="padding: 2px 5px 2px 5px; | ID_COMMON
 +
|-
 +
| style="padding: 2px 5px 2px 5px; | ID_CMD_QUERY_STATE_DATA
 +
| style="padding: 2px 5px 2px 5px; | 0x0e
 +
| style="padding: 2px 5px 2px 5px; | Joint state response
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_SUB_01<br>ID_DEVICE_SUB_02<br>ID_DEVICE_SUB_03<br>ID_DEVICE_SUB_04
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
 +
|-
 +
| style="padding: 5px 5px 2px 5px; | ID_CMD_QUERY_CONTROL_DATA
 +
| style="padding: 2px 5px 2px 5px; | 0x0f
 +
| style="padding: 2px 5px 2px 5px; | Joint state response
 +
| style="padding: 2px 5px 5px 5px; | ID_DEVICE_SUB_01<br>ID_DEVICE_SUB_02<br>ID_DEVICE_SUB_03<br>ID_DEVICE_SUB_04
 +
| style="padding: 2px 5px 2px 5px; | ID_DEVICE_MAIN
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|-
 +
<br>
 +
 
 +
ID_CMD_SET_SYSTEM_ON || 0x01 || Start periodic communication || ID_DEVICE_MAIN || ID_COMMON
  
 
====Source and Destination Identifiers====
 
====Source and Destination Identifiers====

Revision as of 12:06, 19 October 2012

Contents

CAN Communication

Baud-Rate

The CAN communication baud-rate is 1Mbps.

Non-Periodic Communication

Messages can be sent to initialize or stop CAN communication.

Periodic Communication

The Allegro Hand control software attempts to communicate with the real or simulated hand at a regular control interval. Every 3 milliseconds the joint torques are calculated and the joint angles are updated.

CAN Frames

Standard CAN Packet

The standard CAN packet used for communication contains 8 bytes. 

typedef struct{ 
	unsigned char STD_EXT; 
	unsigned long msg_id;		//message identifier 
	unsigned char data_length;	// 
	char           data[8];		// data array 
} can_msg;

ID (Message Identifier)

The 4 byte integer CAN message is split into the command ID (26 bits), destination ID (3bits) and source ID (3 bits).

1 8 16 24 26 27 29 30 32
Command ID Dest. ID Source ID


Command Identifiers


ID_CMD_SET_SYSTEM_ON || 0x01 || Start periodic communication || ID_DEVICE_MAIN || ID_COMMON

Source and Destination Identifiers

TABLE GOES HERE

 whatever

Case-study: Softing CAN

In this chapter, sample code demonstrating the implementation of the CAN communication interface is provide. This is the foundation for Softing PCI CAN.

Opening the CAN Communication Channel

char ch_name[256]; 
sprintf_s(ch_name, 256, "CAN-ACx-PCI_%d", ch); 
INIL2_initialize_channel(&hCAN[ch-1], ch_name); 
 
L2CONFIG L2Config; 
L2Config.fBaudrate = 1000.0; 
L2Config.bEnableAck = 0; 
L2Config.bEnableErrorframe = 0; 
L2Config.s32AccCodeStd = 0; 
L2Config.s32AccMaskStd = 0; 
L2Config.s32AccCodeXtd = 0; 
L2Config.s32AccMaskXtd = 0; 
L2Config.s32OutputCtrl = GET_FROM_SCIM; 
L2Config.s32Prescaler = 1; 
L2Config.s32Sam = 0; 
L2Config.s32Sjw = 1; 
L2Config.s32Tseg1 = 4; 
L2Config.s32Tseg2 = 3; 
L2Config.hEvent = (void*)-1; 
 
CANL2_initialize_fifo_mode(hCAN[ch-1], &L2Config);

CAN Initialization

long Txid; 
unsigned char data[8]; 
 
Txid = ((unsigned long)ID_CMD_SET_PERIOD<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
data[0] = (unsigned char)period_msec; 
canWrite(hCAN, Txid, data, 1, STD); 
 
Sleep(10); 
 
Txid = ((unsigned long)ID_CMD_SET_MODE_TASK<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
canWrite(hCAN, Txid, data, 0, STD); 
 
Sleep(10); 
 
Txid = ((unsigned long)ID_CMD_QUERY_STATE_DATA<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
canWrite(hCAN, Txid, data, 0, STD);

Starting Periodic CAN Communication

When you start periodic CAN communication, joint angles are automatically updated according to the torque control input. 

long Txid; 
unsigned char data[8]; 
 
Txid = ((unsigned long)ID_CMD_QUERY_STATE_DATA<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
canWrite(hCAN[ch-1], Txid, data, 0, STD); 
 
Sleep(10); 
 
Txid = ((unsigned long)ID_CMD_SET_SYSTEM_ON<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
canWrite(hCAN[ch-1], Txid, data, 0, STD);

Stopping Periodic CAN Communication

long Txid; 
unsigned char data[8]; 
 
Txid = ((unsigned long)ID_CMD_SET_SYSTEM_OFF<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
canWrite(hCAN[ch-1], Txid, data, 0, STD);

Transmitting Control Torques

Control inputs for the four joints in each finger should be packed in a single CAN frame. The sample code below demontrates how to encode four PWM inputs into an 8 byte data buffer and how to set the CAN frame ID properly. 

long Txid; 
unsigned char data[8]; 
float torque2pwm = 800.0f 
short pwm[4] = { 
	0.1*torque2pwm, 
	0.1*torque2pwm, 
	0.1*torque2pwm, 
	0.1*torque2pwm 
}; 
 
if (findex >= 0 && findex < 4) 
{ 
	data[0] = (unsigned char)( (pwm[0] >> 8) & 0x00ff); 
	data[1] = (unsigned char)(pwm[0] & 0x00ff); 
 
	data[2] = (unsigned char)( (pwm[1] >> 8) & 0x00ff); 
	data[3] = (unsigned char)(pwm[1] & 0x00ff); 
 
	data[4] = (unsigned char)( (pwm[2] >> 8) & 0x00ff); 
	data[5] = (unsigned char)(pwm[2] & 0x00ff); 
 
	data[6] = (unsigned char)( (pwm[3] >> 8) & 0x00ff); 
	data[7] = (unsigned char)(pwm[3] & 0x00ff); 
 
	Txid = ((unsigned long)(ID_CMD_SET_TORQUE_1 + findex)<<6) | ((unsigned long)ID_COMMON <<3) | ((unsigned long)ID_DEVICE_MAIN); 
	canWrite(hCAN, Txid, data, 8, STD); 
}

Receiving Joint Angles

Each finger consists of four joints. The joint angles for those four joints can be received via one CAN packet. The sample code below demonstrates the method for decoding the data buffer and reading the joint angles.

The sample code assumes that when fingers are in their zero positions, the joint angles from the can packet are 32768. In practice, users should perform experiments and introduce offsets to obtain the zero position. 

char cmd; 
char src; 
char des; 
int len; 
unsigned char data[8]; 
int ret; 
can_msg msg; 
PARAM_STRUCT param; 
 
ret = CANL2_read_ac(hCAN, &param); 
 
switch (ret) 
{ 
case CANL2_RA_DATAFRAME: 
	msg.msg_id = param.Ident; 
	msg.STD_EXT = STD; 
	msg.data_length = param.DataLength; 
 
	msg.data[0] = param.RCV_data[0]; 
	msg.data[1] = param.RCV_data[1]; 
	msg.data[2] = param.RCV_data[2]; 
	msg.data[3] = param.RCV_data[3]; 
	msg.data[4] = param.RCV_data[4]; 
	msg.data[5] = param.RCV_data[5]; 
	msg.data[6] = param.RCV_data[6]; 
	msg.data[7] = param.RCV_data[7]; 
 
	break; 
} 
 
cmd = (char)( (msg.msg_id >> 6) & 0x1f ); 
des = (char)( (msg.msg_id >> 3) & 0x07 ); 
src = (char)( msg.msg_id & 0x07 ); 
len = (int)( msg.data_length ); 
for(int nd=0; nd<len; nd++) 
	data[nd] = msg.data[nd]; 
 
switch (cmd) 
{ 
case ID_CMD_QUERY_CONTROL_DATA: 
	{
		if (id_src >= ID_DEVICE_SUB_01 && id_src <= ID_DEVICE_SUB_04) 
		{ 
			int temp_pos[4]; // raw angle data 
			float ang[4]; // degree 
			float q[4]; // radian 
 
			temp_pos[0] = (int)(data[0] | (data[1] << 8)); 
			temp_pos[1] = (int)(data[2] | (data[3] << 8)); 
			temp_pos[2] = (int)(data[4] | (data[5] << 8)); 
			temp_pos[3] = (int)(data[6] | (data[7] << 8)); 
 
			ang[0] = ((float)(temp_pos[0]-32768)*(333.3f/65536.0f))*(1); 
			ang[1] = ((float)(temp_pos[1]-32768)*(333.3f/65536.0f))*(1); 
			ang[2] = ((float)(temp_pos[2]-32768)*(333.3f/65536.0f))*(1); 
			ang[3] = ((float)(temp_pos[3]-32768)*(333.3f/65536.0f))*(1); 
 
			q[0] = (3.141592f/180.0f) * ang[0]; 
			q[1] = (3.141592f/180.0f) * ang[1]; 
			q[2] = (3.141592f/180.0f) * ang[2]; 
			q[3] = (3.141592f/180.0f) * ang[3]; 
		} 
	} 
 
}

Download

File:AllegroHandCanProtocol.pdf ----------- Work in Progress.
File:AllegroHandCanProtocol KR.pdf

Variable Name Value Description Source Destination
ID_CMD_SET_SYSTEM_ON 0x01 Start periodic communication ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_SYSTEM_OFF 0x02 Stop periodic communication ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_PERIOD 0x03 Set communication frequency ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_MODE_JOINT 0x04 Command Transmission Mode ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_MODE_TASK 0x05 Command Transmission Mode ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_TORQUE_1 0x06 Index finger (1) torque command ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_TORQUE_2 0x07 Middle finger (2) toque command ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_TORQUE_3 0x08 Pinky finger (3) torque command ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_TORQUE_4 0x09 Thumb torque command ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_POSITION_1 0x0a (unused) ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_POSITION_2 0x0b (unused) ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_POSITION_3 0x0c (unused) ID_DEVICE_MAIN ID_COMMON
ID_CMD_SET_POSITION_4 0x0d (unused) ID_DEVICE_MAIN ID_COMMON
ID_CMD_QUERY_STATE_DATA 0x0e Request joint state ID_DEVICE_MAIN ID_COMMON
ID_CMD_QUERY_STATE_DATA 0x0e Joint state response ID_DEVICE_SUB_01
ID_DEVICE_SUB_02
ID_DEVICE_SUB_03
ID_DEVICE_SUB_04 		ID_DEVICE_MAIN
ID_CMD_QUERY_CONTROL_DATA 0x0f Joint state response ID_DEVICE_SUB_01
ID_DEVICE_SUB_02
ID_DEVICE_SUB_03
ID_DEVICE_SUB_04 		ID_DEVICE_MAIN




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