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docs: Minor updates to protocol document 

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2016-12-21 13:54:45 -05:00
parent 29aa6ef6c7
commit 3a478adeaa
1 changed files with 12 additions and 11 deletions
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docs/Protocol.md
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@ -130,23 +130,24 @@ Message Block Contents
Each message block sent from host to firmware contains a series of
zero or more message commands in its contents. Each command starts
with a Variable Length Quantity (VLQ) encoded command-id followed by
zero or more VLQ parameters for the given command. So, the contents of
an example message block might look like:
with a Variable Length Quantity (VLQ) encoded integer command-id
followed by zero or more VLQ parameters for the given command. So, the
contents of an example message block might look like:
```
<id_cmd_a><param1><id_cmd_b><param1><param2><id_cmd_c><id_cmd_d>
```
In order to encode and parse the message contents, both the host and
firmware must agree on a "data dictionary". The data dictionary
associates high-level commands with specific integer command-ids along
with the number of parameters that the command takes. When processing
the data, the parser will know to expect a specific number of VLQ
encoded parameters following a given command. So, in the above
example, both the host and firmware would know that "id_cmd_a" is
always followed by exactly one parameter, "id_cmd_b" two parameters,
and "id_cmd_c" / "id_cmd_d" zero parameters.
firmware must agree on the number of parameters each command has. So,
in the above example, both the host and firmware would know that
"id_cmd_a" is always followed by exactly one parameter, "id_cmd_b" two
parameters, and "id_cmd_c" / "id_cmd_d" zero parameters. The host and
firmware share a "data dictionary" that associates high-level commands
with specific integer command-ids along with the number of parameters
that the command takes. When processing the data, the parser will know
to expect a specific number of VLQ encoded parameters following a
given command.
The message contents for blocks sent from firmware to host follow the
same format. The identifiers in these messages are "response ids", but