RoboSavvy Forum

-127 to 127 values

2008-04-02T22:28:11+01:00

i-Bot wrote:
The values being read are unsigned characters ranging from 0 to 255. The RoboNova does not work in signed except in a few special cases.

If you choose to interpret the unsigned character as a signed character, that is likely to give problems. While it may be true that an accelerometer has a signed output, you need to properly determine the zero point and then make a valid unsigned to signed conversion.

Thank you i-Bot, as soon as i'll get my new servos, i'll do the patching on my code and return with the results.

Statistics: Posted by roboTT — Wed Apr 02, 2008 10:28 pm

-127 to 127 values

2008-04-02T22:22:59+01:00

The values being read are unsigned characters ranging from 0 to 255. The RoboNova does not work in signed except in a few special cases.

If you choose to interpret the unsigned character as a signed character, that is likely to give problems. While it may be true that an accelerometer has a signed output, you need to properly determine the zero point and then make a valid unsigned to signed conversion.

Statistics: Posted by i-Bot — Wed Apr 02, 2008 10:22 pm

-127 to 127 values

2008-04-02T21:45:47+01:00

Gerry52 wrote:
This is what I found, I'm new to this stuf so please correct me if I'm wrong.

Robobasic doesn't handle negative numbers at all! There is no sign bit. The range of the AD(x) inputs is 0 to 5V, it generates a 0 - 255 value in Robobasic, a byte type can be declared here.
However inputs connected to the 2 axis accelemeter generates a value from 400 to 700 (400 = laying on back side (or left side), 700 = laying on front side (or right side). For this an integer should be declared.

Gerry

You're saying about robobasic, and i'm speaking of reading values with C/C++.
The IR reports positive numbers all the time
The 2Axis reports -127 to +127 evein if being read to Integer.

The values are being read by:

bReadRC = ReadFile(hCom, &rxchar, 1, &iBytesRead, NULL);

into the char rxchar
and are returned mostly as numbers between -127 and 127

Statistics: Posted by roboTT — Wed Apr 02, 2008 9:45 pm

-127 to 127 values

2008-04-02T19:56:34+01:00

This is what I found, I'm new to this stuf so please correct me if I'm wrong.

Robobasic doesn't handle negative numbers at all! There is no sign bit. The range of the AD(x) inputs is 0 to 5V, it generates a 0 - 255 value in Robobasic, a byte type can be declared here.
However inputs connected to the 2 axis accelemeter generates a value from 400 to 700 (400 = laying on back side (or left side), 700 = laying on front side (or right side). For this an integer should be declared.

Gerry

Statistics: Posted by Gerry52 — Wed Apr 02, 2008 7:56 pm

-127 to 127 values

2008-04-02T10:26:23+01:00

Sounds like its using a signed byte, try using an integer instead asit will give you more resoltion wont overrun the sign boundary at 32768.

Statistics: Posted by davidalecmcinnes — Wed Apr 02, 2008 10:26 am

-127 to 127 values

2008-03-31T23:17:27+01:00

Guys,

whenever a values are read - the range is between -127 to 127 - why does MR-C set it this way?

Is this correct, or am i doing smth wrong while reading, maybe some coversion is required ?

For example 2axis accel returns values for X/Y as a range between:

-127 to 127.

Any idea?

Statistics: Posted by roboTT — Mon Mar 31, 2008 11:17 pm