解析MWC串口通讯正式版20130407.doc

解析MWC的串口通讯 一使用的软件 二使用的MWC定义串口协议文件 updated 04 JulyMultiwii serial protocol was redesigned:? to be light, as before? to be generic: it can be used transparenlty by a GUI, OSD, telemetry or home made config tool.ie no more specific OSD code should be coded in multiwii? to be bit wire efficient: only requested data are transmitted in a binary format? to be quite secure: data are sent with a checksum, preventing corrupted configuration to be injected.? to be header sensitive: as it is designed with a specific header, it can be mixed with other frame, like GPS frameie, it will be possible to connect either a GUI or a GPS on the same serial port without changing the conf? to be less sensitive to evolutions:ie in case of parameter evolution, the main protocol will remain compatible and the GUI will be much less version dependent.variable data length allows to consider only the beginning of a message, leaving the other octets at the end to extend transparently the message (for instance to add a new PID)I thought first about an implementation of Mavlink, but I think its not what I was looking for.Even with a partial implementation, the predefined structures are not light enough for what I have in mind.Some messages are however inspired from mavlink structure.The main rule remains: Multiwii never sends something on its own.A request must be done in each case to retrieve or set data.Each messages received are acknowledged even if there is no data inside.There are 2 main messages to consider:?request message to multiwii?multiwii output messagerequest message to multiwiiTo request simple data without parameters / send a specific command / inject new parameters in multiwiimessages are formated like this:$M[data length][code][data][checksum]1 octet $1 octet M1 octet 1 octet [data length]1 octet [code]several octets [data]1 octet [checksum][data length] can be 0 in case of no param commandmultiwii output messagemessages are format