31 lines
2.0 KiB
Plaintext
31 lines
2.0 KiB
Plaintext
General:
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- All messages end in a two-byte CRC-16/CCIT-FALSE
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Connection Sequence:
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- For some reason, the first 4 packets are 16 bytes long.
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<- Controller starts by sending a "discover" message(0x0A) every 20ms
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- Unsure what any of the fields in this packet mean, likely that a multi-byte identifier for the controller is included somewhere, and flags
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-> When FC is powered on, it responds to the 0x0A with a 0x03
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- For 0x03 the first two bytes seem to be flags, and bytes 8-11 are the brains 4-byte ID, byte 7 also has bits set, but unsure what they mean
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<- Controller responds to 0x03 with 0x13
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- No idea what any of these fields mean, but sending the same seems to work
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-> FC responds with 0x02 ACK
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- From now on, all packets are 32 bytes long
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<- Controller sends "get poll rate" packet 0x11
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-> FC responds with "set poll rate" 0x04 with byte 2 set to the polling rate in ms
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<- Controller ACKs 0x02
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-> FC ACKs the ACK 0x02
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- I just realized that the 0x14 byte corresponds to 20 in decimal, which is the interval that the controller is sending packets. Changing this to another value changes the controller poll interval so it looks like this sequence configures the controller polling interval.
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Control Sequence:
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- After this startup sequence is completed, the controller starts a sequence of sending 0xA7 packets every 20ms
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<- Controller sends 0xA7 with the robot name, control status flags, system status flags, and timer.
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- At this point the FC can respond in two ways:
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1) -> FC sends 0x02 to ACK the 0xA7, controller continues operation and sends 0xA7 again in 20ms with the same info
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2) -> FC sends 0x53 to update the info with control flags and timer. Controller sends 0xA7 again in 20ms and it should contain the updated info.
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- The way I handle this in the code is to have an "expected state" for the timer and control flags(control flags can be updated over serial).
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- When receiving a 0xA7, if the info matches the "expected" send a 0x02
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- When receiving a 0xA7, if the info does not match the "expected" send a 0x53 with the expected info
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