unsigned to signed converter
Two comments.
1. If an 8-bit integer (0..255) is representing a negative number like -0.023, it's not unsigned. It's e.g. a fixed point or fractional signed number. Of course you can display it as an unsigned, but it still contains a sign information.
2. You have to know the scaling of your target number format respectively the numeric range represented by it, than a conversion is easy. 0..255 may e.g. represent -1..+1. You can read it then as 2's complement signed value with a power of 2 scaling factor. (-128..127 *1/128). In this case, -0.023 converts to -3 respectively 253 or 0xfd when displayed as unsigned.