DLESTXETX Framing Decoder/Encoder This framing decoder extracts packets from a stream of bytes. Imagine a TCP stream of bytes coming in in arbitrary chunks.

Writing Control Characters to a Serial Port in LabVIEW. To write control characters to a serial device. STX (start of text) ctrl B: 3: 03: ETX (end of text). STX/ETX Packet Protocol Library. STX/ETX is a simple packet protocol for serial data streams. STX/ETX is a simple packet protocol that can be wrapped.

The received byte chunks are not necessarily of the same size as they have been sent. For instance, a sender might send the following packets (separated by spaces): aaaa bb cccccccc ddd.

The sequence of bytes transmitted could be received as follows: a aa abbcc ccc cccd dd. A frequent task is hence to split a stream of bytes into a sequence of packets.

A very robust, simple and self-resynchronizing framing is byte stuffing. Spl Drumxchanger Mac Keygen Opener on this page. This (de-)framing mechanism has for instance been used by HDLC ().

This framing decoder/encoder implements a byte stuffing decoder based on a DLE STX. DLE ETX framing. Usage Send instances of org.jboss.netty.buffer.ChannelBuffer (called payload in the following) downstream and this encoder will create a new instance of ChannelBuffer which frames the contents of payload as described above.

Any occurrences of DLE in payload will be byte stuffed. If the decoder is placed into a pipeline, it will read data from the pipeline until a full packet has been received. Any byte-stuffed DLEs are changed back to single DLEs in the resulting payload. Once a packet has been received, the payload is sent upstream as an instance of ChannelBuffer. ##Mode of operation This framing mechanism uses the special ASCII characters 0x10 (called DLE or Data Link Escape), 0x02 (STX, Start of Text), 0x03 (ETX, End of Text).

Each packet is framed as between 'DLE STX' and 'DLE ETX' as follows: DLE STX.arbitrary.bytes.of.payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ DLE STX Payload (DLEs byte-stuffed) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .more payload (arbitrary size (DLEs byte-stuffed) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . DLE ETX +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ So, when sending a packet on a stream, just transmit 'DLE STX', then the payload of bytes (the content of the packet), and finally 'DLE ETX'. When sending the payload data, each DLE character must be doubled (i.e., DLE becomes DLE DLE). Image you want to transmit the payload '0x10', the final packet is 0x10 0x02 0x10 0x10 0x10 0x03 (or DLE STX DLE DLE DLE ETX). A receiver must therefore look for packet start (i.e. DLE STX), read the payload and remove the second DLE if two consecutive ones are received (de-stuffing), and continue buffering until DLE ETX is found. If something goes wrong (e.g., because the stream uses UDP and not TCP and some packets have gone lost), the receiver can always resynchronize to the next start of a packet easily by discarding anything until then.

Protocol Caveat: please note that there seems to be no official documentation about the used protocol. The only valuable source of help was ELV’s documentation of the ULA 200 (an USB-to-LCD converter), which uses the same protocol principle. Everything described below is just the result of snooping the USB bus and analyzing the data when controlling the logger via the Windows software. So, the information here might be (partially) wrong and/or incomplete.

And, of course, it’s always possible that the manufacturer might have incompatibly changed the logger’s firmware meanwhile. Use at your own risk.

The serial interface parameters are 38400,E,1. The protocol is relatively simple: the PC sends a command sequence to the logger and the logger answers with an appropriate message.

All data transfers are in binary format. The following ASCII control codes are used in data transfers: Name Hex-Code STX 0x02 ETX 0x03 ENQ 0x05 ACK 0x06 NAK 0x15 All commands are of the form and will be answered with the sequence: Since all data transfers are done in binary format, the following translation of the characters in and has to be done: if any of the characters, or is to be transmitted, this character must be replaced with the two character sequence. Consequently, the receiving side has to translate this two character sequence back into the original character. Known command sequences If the logger is busy, or there is an error in the command sequence (though some errors will simply be ignored), the field of the answer is always.

So, in the following description, only the answers in case of success are given. The date sequence used in the communication is a sequence of seven bytes in the following format: yearlo yearhi month day hours minutes seconds The year is to be interpreted as a 16bit number (LSB first); month ranges from 0 (January) to 11 (December); the other bytes are to be interpreted as expected.

Note that this interpreting is just done by the controlling software on the PC. The logger itself does not do anything with the date, but just stores it in the eeprom and sends it back later.

So, theoretically, we could send any seven byte sequence to the device here as long as we don’t use the original windows software for controlling the device. Command: V Parameters: none Response: lo hi Description: Get version number. To be interpreted as a 16bit number (LSB first). The original windows software seems to be using this command to periodically check whether the logger is currently active or not. Command: A Parameters: none Response: lo hi Description: Get number of stored data points.

To be interpreted as a 16bit number (LSB first). Command: S Parameters: starttime mode interval Response: Description: Start logging. Starttime is a date sequence as described above; mode is 2 for temperature only and 3 for temperature plus humidity; interval is either 1 or 5.

Command: E Parameters: stoptime Response: Description: Stop logging. Stoptime is a date sequence as described above. Command: Z Parameters: none Response: starttime mode interval stoptime Description: Get starttime, endtime, mode and interval. See S and E commands for the meaning of the response. Command: R Parameters: none Response: tlo thi hum. Description: Get first data record.

Depending on the logging mode, either two or three bytes per data point will be sent. The temperature values are to be interpreted as 16bit values (LSB first) with 1/10°C unit. The humidity value can be taken directly. Note that since the USB protocol is block oriented, the data record may contain more data points than available. These excess points have to be ignored.

Command: N Parameters: none Response: tlo thi hum. Description: Get next data record if there are more stored data points than can be retrieved by the R command. The same comment as for the R command applies. Command: G Parameters: none Response: tlo thi hum. Description: Unknown command. Response is the same as from the previous R or N command.