Expand v4 `led0` range to 0..255

[sneakers-the-rat]

Related to:

• https://github.com/Aharoni-Lab/Miniscope-DAQ-QT-Software/issues/68
• https://github.com/Aharoni-Lab/Miniscope-v4/issues/37#issuecomment-1922748249

Problem

Some lucky people have such lovely bright and clear signal that they need to make the illumination LED as dim as possible.

The current led0 configuration maps 0..100 -> 0..255, which naturally reduces the number of possible brightness states from 256 to 101, the relevant line in the software is here:

https://github.com/Aharoni-Lab/Miniscope-DAQ-QT-Software/blob/0fecb97cca82c694b1b40dde03cd759e23ad3224/source/VideoSliderControl.qml#L73

So for the current settings:

• displayValueScale: -2.55
• displayValueOffset: -255

the value map created is:

Expand/collapse value map

input	output
0	255
1	252
2	250
3	247
4	245
5	242
6	240
7	237
8	235
9	232
10	230
11	227
12	224
13	222
14	219
15	217
16	214
17	212
18	209
19	207
20	204
21	201
22	199
23	196
24	194
25	191
26	189
27	186
28	184
29	181
30	178
31	176
32	173
33	171
34	168
35	166
36	163
37	161
38	158
39	156
40	153
41	150
42	148
43	145
44	143
45	140
46	138
47	135
48	133
49	130
50	128
51	125
52	122
53	120
54	117
55	115
56	112
57	110
58	107
59	105
60	102
61	99
62	97
63	94
64	92
65	89
66	87
67	84
68	82
69	79
70	76
71	74
72	71
73	69
74	66
75	64
76	61
77	59
78	56
79	54
80	51
81	48
82	46
83	43
84	41
85	38
86	36
87	33
88	31
89	28
90	26
91	23
92	20
93	18
94	15
95	13
96	10
97	8
98	5
99	3
100	0

Fix

That seems to only really be a problem on the low end, where someone could access 2/3 and 1/3 of the current minimum brightness.

The reason for wanting to constrain from 0..100 is to make proportions sensible - 100% brightness is more intuitive than the max being 255, but it seems like at the point that it's limiting functionality it might be worth expanding to the full range.

This PR is just one way of doing this without needing to recompile anything. It changes the range to 0..255, the scale to 1, and the offset to 255 for a map of (x*1)-255

Other options

• make another directory examples with a README.md document in it, where we make this modified deviceConfig file an example with the full LED range and explain what it does in the README
• make the StepSize smaller, like 0.1 or something - this would keep the 0..100 range while allowing someone to access the full 0..255 output range, but imo it's somewhat undesirable because a lot of changes to float values would actually not change the output value at all, which would lead to bad intuition traps trying to micro-adjust values that aren't actually doing anything.
• make another v4 device config something like v4_full_led0_range - but that seems undesirable because we get into combinatorics of "for every variant we square the number of devices we have"
• ideally this would be something one could toggle in the UI, but that's about a thousand times more work than changing 4 lines in the config for now ;)

Anyway what do ya think?