Recombining 2 bytes into a signed int

Processing Coding Questions
1

Sending a byte stream over from an Arduino which includes some int16_t values (little endian) but struggling to recombine them. This is as close as I can get, but I loose the sign.

          int1 = (inBuffer[1]<<8) | inBuffer[0]&0xff;
          int2 = (inBuffer[3]<<8) | inBuffer[2]&0xff;
          int3 = (inBuffer[5]<<8) | inBuffer[4]&0xff;
          int4 = (inBuffer[7]<<8) | inBuffer[6]&0xff;

Thanks.

2

forum.Processing.org/two/discussion/17900/out-of-control-y-axis-rolling-graph#Item_1

3

Thanks but I can’t see an answer to my question there.

I need to use a byte stream for speed.

Sending ASCII and dealing with strings and tokens is way too slow for my requirements.

4

Java’s corresponding datatype is short.

I’ve got this example sketch which uses a FloatBuffer:
forum.Processing.org/two/discussion/12757/transmission-of-a-float-through-a-serial-link#Item_5

But you can easily adapt it to use a ShortBuffer instead:
docs.Oracle.com/javase/8/docs/api/java/nio/ByteBuffer.html#asShortBuffer–

However I think you’re gonna need to switch your Arduino code to send bytes as big endian, which is the default protocol for transmission AFAIK.

5

Hello,

Did you try:

int1 = ( (0xff & inBuffer[1]) << 8) |  ( (0xff & inBuffer[0]) << 8)

I think that should work.

6

It does not work.

Correction:

image
image971×523 26.5 KB

:)

1 Like
7

oops, thanks for the correction =)

1 Like