Mavlink命令中的[180]是什么意思？

Question

I am trying to send a mavlink command for instance

GPS_RTCM_DATA ( #233 )

flags   uint8_t     

len     uint8_t

data    uint8_t[180]        RTCM message (may be fragmented)

https://mavlink.io/en/messages/common.html#GPS_RTCM_DATA

I understand uint8_ would be in a single byte unsigned int. What does the [180] means?

Answer 1

The uint8_t[180] in the MAVLink GPS_RTCM_DATA message means that the data field can contain up to 180 bytes.

Beware that RTCM messages can be bigger than 180 bytes and be fragmented in more than one GPS_RTCM_DATA message.

You can check the flags field as stated in the mavlink documentation:

LSB: 1 means message is fragmented, next 2 bits are the fragment ID, the remaining 5 bits are used for the sequence ID. Messages are only to be flushed to the GPS when the entire message has been reconstructed on the autopilot. The fragment ID specifies which order the fragments should be assembled into a buffer, while the sequence ID is used to detect a mismatch between different buffers. The buffer is considered fully reconstructed when either all 4 fragments are present, or all the fragments before the first fragment with a non full payload is received. This management is used to ensure that normal GPS operation doesn't corrupt RTCM data, and to recover from a unreliable transport delivery order.

Answer 2

I tried every but it doesn't work. Except putting it as a 180 byte arrays. The data might be only 30 bytes for example. But input with the other 150 0x00 bytes in this way, the python program accepts my command. Strangely so. I can't explain why but in this case it works.