Wrapping AVR Commands

So to SEND an AVR command to the EDBG, it is wrapped as:

Table 1. AVR_CMD Command
Field	Size	Description
AVR_CMD	1 byte	0x80
FragmentInfo	1 byte	Fragment number
Size	2 bytes, MSB first	Number of bytes in the wrapped AVR packet
CommandPacket	N bytes	Enveloped AVR packet

Large packets must be chopped up according to the HID interface’s REPORT_SIZE. The fragment number envelope field is two 4-bit nibbles indicating a "packet m of n packets" relationship:

(packet_number << 4) | total_number_of_packets.

Each SEND fragment responds with:

Table 2. AVR_CMD Response
Field	Size	Description
AVR_CMD	1 byte	0x80
FragmentCode	1 byte	0x00: More fragments required (m < n) 0x01: Full packet received, will be processed (m == n)

This is not to be confused with the AVR_RSP, which is the response to the command itself, which is detailed next.

For example, to wrap a 100B AVR command packet when the REPORT_SIZE is 64B:

Table 3. AVR_CMD Example
Packet#	Direction	Data
1	PC to Tool	0x80 0x12 0x00 0x3C ...First 60B of AVR command packet...
2	Tool to PC	0x80 0x00
3	PC to Tool	0x80 0x22 0x00 0x28 ...Remaining 40B of AVR command packet...
4	Tool to PC	0x80 0x01