CDNET is a high layer protocol for CDBUS

1. CDNET Levels
2. Level 0 Format
3. Level 1 Format
4. Level 2 Format
5. Specific Ports
6. Examples
7. More Resources

CDNET Levels

CDNET protocol has three different levels, select by bit7 and bit6 of first byte:

Bit7	Bit6	DESCRIPTION
0	x	Level 0: The simplest one, for single network communication
1	0	Level 1: Support cross network and multi-cast communication
1	1	Level 2: Raw, e.g. TCP/IP communication between PCs

You can select one or more levels for your application as needed.

The CDNET is little endian.

Level 0 Format

Request

First byte:

FIELD	DESCRIPTION
[7]	Always 0: Level 0
[6]	Always 0: request
[5:0]	dst_port, range 0~63

The second byte and after: command parameters.

Note: The port is equivalent to UDP port, but can be simply understood as commands.

Reply

First byte:

FIELD	DESCRIPTION
[7]	Always 0: Level 0
[6]	Always 1: reply
[5]	0: not share; 1: [4:0] shared for first data byte
[4:0]	Not care, or part of first data byte

Default: SHARE_MASK is 0xe0, SHARE_LEFT is 0x80, only allow share if (first data byte & SHARE_MASK) == SHARE_LEFT.

E.g.: reply [0x40, 0x8c] is the same as [0x6c].

0x40: 'b0100_0000
0x8c: 'b1000_1100
----
0x6c: 'b0110_1100

The first byte shared part, and the second byte and after: reply status and/or datas.

Recommendation for level 0 and 1:

For request and report, the first parameter byte is sub command with two flags:

FIELD	DESCRIPTION
[7]	is_reply, always 0
[6]	not_reply, e.g. 1 for report packet
[5:0]	sub command

For reply, the first data byte is status with one flag:

FIELD	DESCRIPTION
[7]	is_reply, always 1
[6:0]	status, 0 means no error

Level 1 Format

First byte:

FIELD	DESCRIPTION
[7]	Always 1
[6]	Always 0
[5]	MULTI_NET
[4]	MULTICAST
[3]	SEQUENCE
[2:0]	PORT_SIZE

MULTI_NET & MULTICAST

MULTI_NET	MULTICAST	DESCRIPTION
0	0	Local net: append 0 byte
0	1	Local net multicast: append 2 bytes [multicast-id]
1	0	Cross net: append 4 bytes: [src_net, src_mac, dst_net, dst_mac]
1	1	Cross net multicast: append 4 bytes: [src_net, src_mac, multicast-id]

Notes:

• Broadcast could simply not use the MULTICAST bit.

SEQUENCE

0: No sequence number;
1: Append 1 byte SEQ_NUM, see Port 0.

PORT_SIZE:

Bit2	Bit1	Bit0	SRC_PORT	DST_PORT
0	0	0	Default port	1 byte
0	0	1	Default port	2 bytes
0	1	0	1 byte	Default port
0	1	1	2 bytes	Default port
1	0	0	1 byte	1 byte
1	0	1	1 byte	2 bytes
1	1	0	2 bytes	1 byte
1	1	1	2 bytes	2 bytes

Notes:

• Default port is 0xcdcd for convention, it does not take up space.
• Append bytes for src_port first then dst_port.

Level 2 Format

First byte:

FIELD	DESCRIPTION
[7]	Always 1
[6]	Always 1
[5:4]	FRAGMENT
[3]	SEQUENCE
[2:0]	User-defined flag

FRAGMENT:

Bit5	Bit4	DST_PORT
0	0	Not fragment
0	1	First fragment
1	0	More fragment
1	1	Last fragment

Note:

• SEQUENCE must be selected when using fragments.
• There is no need to reset the SEQ_NUM when starting the fragmentation.

SEQUENCE

0: No sequence number;
1: Append 1 byte SEQ_NUM, see Port 0.

Specific Ports

Ports 0 through 9 are cdnet-specific (undefined ports are reserved), Port 10 and later are freely assigned by user.

All specific ports are optional, and user can only implement some of the port features. It is recommended to implement at least the basic part of port 1 (device info).

Port 0

Used together with header's SEQUENCE for flow control and ensure data integrity.
The SEQ_NUM[6:0] auto increase when SEQUENCE is selected in the header.
Bit 7 of SEQ_NUM is set indicating that a report is required.
Do not select SEQUENCE for port 0 communication self.

Port 0 communications:

Check the SEQ_NUM:
  Write [0x00]
  Return: [0x80, SEQ_NUM] (no record found if bit 7 set)

Set the SEQ_NUM:
  Write [0x20, SEQ_NUM]
  Return: [0x80]

Report SEQ_NUM:
  Write [0x40, SEQ_NUM]
  No Return

Example:
(-> and <- is port level communication, >> and << is packet level communication)

  Device A                      Device B        Description

  [0x20, 0x00]          ->      Port0           Set SEQ_NUM at first time
                        <-      [0x80]          Set return
  [0x88, 0x00, ...]     >>                      Start send data
  [0x88, 0x01, ...]     >>
  [0x88, 0x82, ...]     >>                      Require report at SEQ_NUM 2
  [0x88, 0x03, ...]     >>
  [0x88, 0x04, ...]     >>
  Port0                 <-      [0x40, 0x03]    Report after receive SEQ_NUM 2
  [0x88, 0x85, ...]     >>                      Require report at SEQ_NUM 5
  Port0                 <-      [0x40, 0x06]    Report after receive SEQ_NUM 5

Port 1

Provide device info.

Type of mac_start and mac_end is uint8_t;
Type of max_time is uint16_t, unit: ms;
Type of "string" is any length of string, include empty.

Check device_info string:
  Write [0x00]
  Return [0x80, "device_info"]

Search device by filters (need by mac auto allocation):
  Write [0x01, max_time, mac_start, mac_end, "string"]
  Return [0x80, "device_info"] after a random time in range [0, max_time]
    only if "device_info" contain "string" (always true for empty string) and
    current mac address is in the range [mac_start, mac_end]
  Not return otherwise

Example of device_info:
M: model; S: serial string; HW: hardware version; SW: software version ...
Do not care about the field order, and should at least include the model field.

Port 2

Set device baud rate.

Type of baud_rate is uint32_t, e.g. 115200;
Type of intf is uint8_t.

Set current interface baud rate：
  Write [0x20, baud_rate]                       // single baud rate
  Write [0x21, baud_rate_low, baud_rate_high]   // dual baud rate
  Return: [0x80]                                // change baud rate after return

Set baud rate for specified interface:
  Write [0x22, intf, baud_rate]
  Write [0x23, intf, baud_rate_low, baud_rate_high]
  Return: [0x80]

Check baud rate for specified interface:
  Write [0x00, intf]
  Return: [0x80, baud_rate] or [0x80, baud_rate_low, baud_rate_high]

Port 3

Set device address.

Type of mac and net is uint8_t;
Type of intf is uint8_t;
Type of "string" is any length of string, include empty.

Change mac address for current interface:
  Write [0x20, new_mac, "string"]:                  // "string" is optional (need by mac auto allocation)
  Return [0x80] if "device_info" contain "string"   // change mac address after return
  Not return and ignore the command otherwise

Change net id for current interface:
  Write [0x21, new_net]
  Return: [0x80]                                    // change net id after return

Check net id of current interface:
  Write [0x01]
  Return: [0x80, net]

Set mac address for specified interface:
  Write [0x28, intf, new_mac]
  Return: [0x80]

Set net id for specified interface:
  Write [0x29, intf, new_net]
  Return: [0x80]

Check mac address for specified interface:
  Write [0x08, intf]
  Return: [0x80, mac]

Check net id for specified interface:
  Write [0x09, intf]
  Return: [0x80, net]

Examples

Request device info:
(Local network, requester's MAC address: 0x0c, target's MAC address: 0x0d)

Reply the device info string: "M: c1; S: 1234", expressed in hexadecimal: [0x4d, 0x3a, 0x20, 0x63, 0x31, 0x3b, 0x20, 0x53, 0x3a, 0x20, 0x31, 0x32, 0x33, 0x34].

The Level 0 Format:

• Request:
  • CDNET socket: [00:00:0c]:0xcdcd -> [00:00:0d]:1: 0x00 (net id: 0)
  • CDNET packet: [0x01, 0x00] (dst_port = 0x01)
  • CDBUS frame: [0x0c, 0x0d, 0x02, 0x01, 0x00, crc_l, crc_h]
• Reply:
  • CDNET socket: [00:00:0d]:1 -> [00:00:0c]:0xcdcd: 0x80 + "M: c1; S: 1234"
  • CDNET packet: [0x60, 0x4d, 0x3a, 0x20 ... 0x34] (first 0x60 is 0x40 + 0x80)
  • CDBUS frame: [0x0d, 0x0c, 0x0f, 0x60, 0x4d, 0x3a, 0x20 ... 0x34, crc_l, crc_h]

The Level 1 Format:

• Request:
  • CDNET socket: [80:00:0c]:0xcdcd -> [80:00:0d]:1: 0x00
  • CDNET packet: [0x80, 0x01, 0x00] (src_port = default, dst_port = 0x01)
  • CDBUS frame: [0x0c, 0x0d, 0x03, 0x80, 0x01, 0x00, crc_l, crc_h]
• Reply:
  • CDNET socket: [80:00:0d]:1 -> [80:00:0c]:0xcdcd: 0x80 + "M: c1; S: 1234"
  • CDNET packet: [0x82, 0x01, 0x80, 0x4d, 0x3a, 0x20 ... 0x34] (src_port = 0x01, dst_port = default)
  • CDBUS frame: [0x0d, 0x0c, 0x11, 0x82, 0x01, 0x80, 0x4d, 0x3a, 0x20 ... 0x34, crc_l, crc_h]

Code Examples

How to use this library refer to stepper_motor_controller, cdbus_bridge or cdnet_tun projects;
How to control CDCTL-Bx/Hx refer to dev/cdctl_xxx.

More Resources

Python library for CDNET: ../pycdnet

CDNET address string format: parser/cdnet.h