groundside script to open and read data from files in pixhawk file system #69
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| ftp_payload[6] = 0 # burst_complete | ||
| ftp_payload[7] = 0 # padding | ||
| ftp_payload[8:12] = struct.pack("<I", offset) | ||
| ftp_payload[12 : 12 + len(payload)] = payload |
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Please check to make sure this doesn't overflow
| opcode (int): FTP command opcode. | ||
| req_opcode (int): Requested opcode. | ||
| session (int): Session ID. | ||
| offset (int): Offset in the file. | ||
| size (int): Size of the payload. | ||
| payload (bytes): Payload data. |
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Add comment giving the range (and/or size) of all of these numbers
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Can you move this file to modules/mavlink folder. Also rename the file to ftp_example.py. We probably won't be using this as the communication method for comp, but it may be useful for logging in the future.
| send_ftp_command( | ||
| vehicle, | ||
| seq_num=SEQ_NUM, | ||
| opcode=4, |
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Make an enum for opcode so that people don't have to constantly look up the FTP docs
| # open file for reading session | ||
| send_ftp_command( | ||
| vehicle, | ||
| seq_num=SEQ_NUM, |
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This should not be a constant, it should increment by 1 (mod 65535+1) every time you send a message (ie if you receive a message that has seq_num=123, you should send the next message with seq_num=124).
| size=len(FILE_PATH), | ||
| payload=FILE_PATH, | ||
| ) | ||
| SEQ_NUM += 1 |
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You increment this from the value you received in the response FTP message. Also, capital variables are meant to be constants and shouldn't change. You can rename this to lower case, and write out the full name.
| # retrieve session id, file size, and sequence number from ACK response | ||
| SESSION_ID = response_payload[2] | ||
| DATA_OFFSET = struct.unpack("<I", response_payload[8:12])[0] | ||
| FILE_SIZE = struct.unpack("<I", response_payload[12 : 12 + response_payload[4]])[0] | ||
| SEQ_NUM = struct.unpack("<H", response_payload[0:2])[0] | ||
| CHUNK_SIZE = 239 # Max data size per chunk | ||
| FILE_DATA = b"" |
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Instead of doing this, make a function that returns a "FTP_Response" object with these as fields. You should also do sequence_num += 1 mod 2^16, so people don't have to remember to do that
| if response_payload[3] != 128: # Check for error - NAK Response | ||
| print("ERROR RECEIVED") | ||
| print("ERROR CODE: ", response_payload[12]) | ||
| sys.exit() |
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This is ok for now, but in practice we never just quit the program, that may cause drone to fall out of the sky.
| response_payload = bytes(response.payload) | ||
| if response_payload[3] != 128: # Check for error - NAK Response | ||
| print("ERROR RECEIVED") | ||
| print("ERROR CODE: ", response_payload[12]) |
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This thing could be 2 bytes, you should check the size byte. Also, make an enum for error codes so that you don't print a number but the actual error message.
| FILE_DATA += chunk_data | ||
| DATA_OFFSET += len(chunk_data) | ||
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| print(chunk_data.decode("utf-8", errors="ignore"), end="") |
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Rather than printing things one chunk at a time, you should print the entire file at once at the very end. Python print statements add newline characters, which will make your file look like it has random newlines everywhere. Also, if the bytes broke in a bad spot (ie if there was an integer in the file which is 4 bytes but you only received 1, you're going to print garbage)
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