How can I convert groups of incoming bytes received via serial to a singel int.

donuan

Hi,

I am using processing to communicate via serial with a fingerprint sensor (GT-511C3) and the messages it sends looks something like this: 55-AA-01-00-0F-10-00-00-31-00-50-01.

as these are sent separately and constantly I cannot in this state listen for a specific byte changing (e.g. the 0F changing to 00) so I would like to convert these sets of bytes to ints so that I can use them to trigger specific events.

Any idea of how I would go about to do that would be much appreciated.

here is the code Im using to receive them:

void serialEvent(Serial p) { byte rx_byte;

while (p.available() > 0) { // get a single character from the serial port rx_byte = (byte)serial_port.readChar(); println(hex(rx_byte)); } }

Thanks!

KevinWorkman

I'm not sure I understand your question. A byte is a subset of int. If you have a byte, you can just treat it as an int. This works fine:

void setup(){
 byte b = 7;
 int i = b;
 println(i);
}

Is there something else you're trying to do? Can you post a small example with hardcoded values (and code tags) like mine (get rid of the serial stuff) that shows where you're stuck?

donuan

Thanks for the answer, Maybe I didn't explain myself very well. Im pretty new to processing so maybe my question is not the correct one for my problem.

I am sending messages via serial to a sensor and the sensor answers by sending back YES or NO represented by a set of twelve bytes, but since they come continuously I do not know how I can interpret them as Yes/no. so I was thinking that if I could take the 12 bytes and convert them to one int I could use that to trigger functions.

Another approach could maybe be to only listen to some of the bytes (say byte number 6 out of the 12) and ignore rest but I would then still need some way of grouping the sets of bytes to separate them out from each other.

I can unfortunately not show you much code that would be useful as this part of the functionality is not there.

Thanks again!

GoToLoop

• http://forum.Processing.org/two/discussion/12386/arduino-to-processing-importing-variables
• http://forum.Processing.org/two/discussion/12490/is-it-possible-to-create-an-indexed-list-array-of-rgb-values-for-fill
• http://studio.ProcessingTogether.com/sp/pad/export/ro.9qxrHCEYG6Z9o

koogs

PDF link http://cdn.sparkfun.com/datasheets/Sensors/Biometric/GT-511C3_datasheet_V1 1_20130411[4].pdf

page 6 has the format of the response

55|AA|01-00|0F-10-00-00|31-00|50-01

byte 0 is always 55
byte 1 is always aa
bytes 2 and 3 are device id - always 0001 (little endian)
4-7 are 'parameter' - 0000100f
8-9 are 'response' - 0031
10-11 is checksum 0150

page 10 says:
0x100F
NACK_DEV_ERR
Device Error, especially if Crypto Chip is trouble

donuan

Thanks!