Why if (t >= 32768) t = 65536l - t about mcp342x

[kerrydwong]

That's calculating 2's complement.
On Dec 16, 2015 5:21 PM, "Kees Bakker" [email protected] wrote:

Hi,

Why is there this piece of code in MCP342X.cpp? What is it trying to do?

if (t >= 32768) t = 65536l - t;

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#1.

[keestux]

Hmm, I assumed you were trying to do that, but are you sure it is working correctly?
Take a look at a few examples of input (16 bits resolution).

value h	value l	value t
0	1	1
127	255	32767
128	0	32768
128	1	32767
255	255	1

That can't be right. It will never give a negative value, which is required when the MSB is 1.

For 14 bits and 12 bits it is not working either. The values never get over 8191 (14 bits), and 2047 (12 bits).

[kerrydwong]

Looks like it should be t - 65536. I think the code provided was only for
16 bit resolution if I remember correctly.
On Dec 17, 2015 2:23 PM, "Kees Bakker" [email protected] wrote:

Hmm, I assumed you were trying to do that, but are you sure it is working
correctly?
Take a look at a few examples of input (16 bits resolution).
value h value l value t 0 1 1 127 255 32767 128 0 32768 128 1 32767 255
255 1

That can't be right. It will never give a negative value, which is
required when the MSB is 1.

For 14 bits and 12 bits it is not working either. The values never get
over 8191 (14 bits), and 2047 (12 bits).

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#1 (comment).

[skyice78]

try to use the library with particle photon and have no luck with it. I like this library because it is much simpler. Anyone got it to work on particle photon?