Mechanicals:

Based on some very unclear measurements, assume 57mm from outside row of connector to outside row M conn to outside row of F conn.
HOWEVER - This is not symmetrical inside the box! Everything is shifted towards the F connector side!

Enclosure inside dim, narrower = ~42.2mm
Assume 40mm wide PCB
Length 63mm - and hope the vias for the connectors at the ends will be OK!

Inside height: 20.6 but use 20.5
Large posts ~17.1
3.4mm for board and components.
0.06" substrate boards from OSHpark, max 74 mil = 1.88 mm
Leaves just over 1.5mm on thinner side for very thin components.

Typical height for 0603 and 0805 resistors is 0.5 max, so most of those should be okay. (Double-check to be sure.)
Found Samsung 0603 100n caps with 0.9mm max height
Found Murata 0603 1.0u caps with 0.9mm max height
Opamp < 1.4mm and MOSFETs < 0.9mm.
Batt charge controller IC < 1.4mm.
LDO < 1.45mm.

Mini-MELF / SOD-80 diodes 1.3-1.5mm. Only 2 of these, maybe best on battery side.

Connectors: 2 rows, 8 pins each. Pins 4mm pitch center-to-center. Rows 3mm centerline-to-centerline. Holes 1mm dia.


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https://www.digikey.com/en/products/detail/nexperia-usa-inc/74LVC595AD-118/1692642

Max Vdd = 3.6V
Good static zap resistances
up to 25 mA output (though at cost of output voltage)
Voh = ~(Vdd - 0.6) at ~15+ mA
Clocking a little jank, need to find a way to reliably drive STCP on falling(?) edge of SRCP.
Schmitt action on all inputs is very nice.
$0.38 qty 10

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8 channel DMOS buffer. Technically a gate driver, but should work just fine as a 15mA LED driver.
Very sane pin config, as opposed to that demon-bastard 74xx244!

https://www.mouser.com/ProductDetail/Toshiba/TBD62781AFWGEL?qs=%252BEew9%252B0nqrA3cGVVM7sCaQ%3D%3D

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DB15 male right angle connectors:

0.283" deep - https://www.digikey.com/en/products/detail/norcomp-inc/173-E15-113R001/1104183
0.374" deep - https://www.digikey.com/en/products/detail/assmann-wsw-components/A-DS-15-AA-Z/15204106

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OBD2 connector:

https://www.aliexpress.us/item/3256801453845180.html - Get black 90 deg version. Connector AND plastic case!

Ordered x2, one black one red, 2022/11/17


DB15 Female to OBD2 Male Adapter -
http://www.obd2plugs.com/Product-47.html

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Constant current LED driver based on 10:1 current mirror and NMOS series pass.

$ 1 0.000005 13.654669808981877 48 5 43
r 688 576 688 624 0 5
34 GaP-2.4v-SuperGreen 0 9.32e-11 0.042 4.9 0
162 688 304 688 368 2 GaP-2.4v-SuperGreen 0 1 0 0.02
g 688 624 688 640 0
R 688 304 688 272 0 1 40 2.5 5 0 0.5
w 688 416 688 432 1
f 608 448 688 448 32 0.7000000000000001 1
r 688 464 688 512 0 0.11
s 688 368 688 416 0 0 false
x 704 450 796 472 4 16 Toshiba\\nSSM3K345R
w 688 576 640 576 0
t 592 576 576 576 0 -1 0 0 100
r 592 576 640 576 0 2
g 576 592 576 608 0
w 528 528 576 560 3
R 528 336 528 304 0 0 40 1.8 0 0 0.5
r 480 336 480 384 0 840
w 528 336 576 336 0
w 576 336 576 384 0
t 528 400 480 400 0 -1 0 0 100
t 528 400 576 400 0 -1 0 0 100
w 528 432 528 400 0
w 528 432 480 432 0
w 480 416 480 432 0
w 608 416 608 448 1
w 480 336 528 336 0
r 528 432 528 528 0 8000
w 576 416 608 416 2
r 608 448 608 496 0 1400
g 608 496 608 512 0
w 688 512 688 576 0
o 3 32 0 4354 20 0.1 0 2 3 3
o 4 32 0 4353 0.0001 0.029994355792806685 1 2 4 3

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15mA constant current source with 1.1V total voltage using LM10 (aka Bob Widlar is a fucking genius):

$ 1 0.000005 13.654669808981877 48 5 43
v 368 480 368 384 0 0 40 0.2 0 0 0.5
g 368 480 368 496 0
r 416 384 416 432 0 155000
r 416 432 416 480 0 45000
w 368 480 416 480 0
w 368 384 416 384 0
r 656 512 656 560 0 3
34 GaP-2.4v-SuperGreen 0 9.32e-11 0.042 4.9 0
162 656 304 656 368 2 GaP-2.4v-SuperGreen 0 1 0 0.02
g 656 560 656 576 0
R 656 304 656 272 0 1 40 2.5 5 0 0.5
w 464 432 480 432 2
w 480 512 480 464 2
w 656 416 656 432 1
w 416 432 464 432 0
w 656 512 480 512 0
f 624 448 656 448 32 0.7000000000000001 1
r 656 464 656 512 0 0.11
r 576 528 576 576 0 100000
g 576 576 576 592 0
w 576 448 576 528 0
r 576 448 624 448 0 22
a 480 448 576 448 9 3.2 0.1 1000000 0 0 100000
s 656 368 656 416 0 0 false
x 703 452 795 474 4 16 Toshiba\\nSSM3K345R
o 9 32 0 4354 20 0.1 0 2 9 3
o 12 32 0 4353 0.0001 0.014997177896403343 1 2 12 3

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10:1 ratio, 15mA constant current souce:

$ 1 0.000005 10.20027730826997 50 5 43
t 544 304 496 304 0 -1 0 -0.5461282467560298 100
t 544 304 592 304 0 -1 0.23874399909547517 -0.6656235441608982 100
w 592 288 592 240 0
w 592 240 544 240 0
w 496 240 544 240 0
R 544 240 544 208 0 0 40 3.3 0 0 0.5
r 496 240 496 288 0 800
g 576 512 576 528 0
w 592 320 624 352 1
w 544 304 544 336 0
w 544 336 496 336 0
w 496 336 496 320 0
g 496 448 496 464 0
174 496 384 464 432 1 5000 0.44060000000000005 Resistance
w 464 416 464 384 0
w 464 384 496 384 0
r 496 336 496 384 0 6000
S 624 352 624 416 0 2 false 0 3
r 672 464 672 512 0 18
g 672 512 672 528 0
g 624 512 624 528 0
r 624 464 624 512 0 180
w 608 416 576 464 0
w 624 416 624 464 0
w 640 416 672 464 0
34 GaP-2.4v-SuperGreen 0 9.32e-11 0.042 4.9 0
162 576 464 576 512 2 GaP-2.4v-SuperGreen 0 1 0 0.01

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10:1 ratio, 15mA constant current sink:

$ 1 0.000005 10.20027730826997 50 5 43
t 352 368 400 368 0 1 0 0 300
t 352 368 304 368 0 1 0 0 300
r 304 384 304 432 0 1200
g 352 432 352 448 0
w 304 432 352 432 0
w 400 432 400 384 1
w 352 432 400 432 0
R 304 224 304 192 0 0 40 3.3 0 0 0.5
v 736 432 736 304 0 1 40 0.3 3.1 0 0.5
w 400 432 736 432 0
162 464 304 416 336 2 default 0 1 0 0.02
w 256 256 256 224 0
w 464 304 736 304 2
w 416 336 400 352 0
w 352 368 352 336 0
w 352 336 304 336 0
w 304 336 304 352 0
w 256 224 304 224 0
174 304 288 256 240 1 10000 0.6881 Resistance
r 304 288 304 336 0 10000
x 72 357 288 398 4 16 Matched\sNPN\spair\\n(E.g.\sDiodes\sInc\sBCM846BS-7\\nbeta\s\q\s300\s@\sIc\q20mA)
o 8 64 0 12290 0.0001 0.0001 0 2 8 3
o 13 64 0 4097 5 0.05 1 2 13 3

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Full 4-bit cable tester:

$ 1 0.000049999999999999996 1.2700821376227165 25 5 43
r 1648 1520 1648 1568 0 130
g 1648 1568 1648 1584 0
162 1648 1408 1648 1472 2 default-led 1 1 0 0.02
s 1248 1024 1328 1024 0 0 false
r 1328 1024 1392 1024 0 33000
d 1392 1056 1328 1056 2 default
r 1328 1056 1328 1120 0 33000
c 1392 1120 1392 1056 0 1e-7 0.001
w 1328 1120 1392 1120 0
g 1392 1120 1392 1136 0
w 1392 1024 1392 1056 0
w 1328 1024 1328 1056 0
w 1392 1024 1456 1024 2
w 1456 1024 1456 1056 0
w 2128 1504 2128 1536 0
w 2320 1488 2320 1168 0
r 1744 1040 1808 1040 0 187000
R 1248 1024 1216 992 0 0 40 3.3 0 0 0.5
c 1808 1104 1808 1040 0 0.0000022 0.001
g 1808 1104 1808 1120 0
w 1808 1104 1872 1104 0
r 1808 1040 1872 1040 0 2200
w 1808 1008 1808 1040 0
w 2320 1136 2320 1168 0
168 1360 1296 1424 1296 1024 4
w 1568 1040 1744 1040 0
151 2320 1152 2176 1152 2 2 0 5
151 2128 1520 2032 1520 2 2 0 5
w 2080 992 2320 992 0
151 1808 992 1984 992 2 2 0 3.3
150 1456 1040 1568 1040 2 2 0 3.3
151 1568 928 1664 928 2 2 0 3.3
g 1728 976 1728 992 0
r 1728 928 1664 928 0 2200
c 1728 976 1728 928 0 0.000001 0.001
w 1568 880 1728 880 0
w 1568 912 1568 944 0
w 1568 912 1568 880 0
w 1568 1040 1568 944 0
w 1808 976 1808 1008 2
w 1872 912 1936 912 0
w 2080 896 2080 992 0
w 2080 896 1984 896 0
g 2032 928 2032 944 0
R 2080 816 2080 784 0 0 40 3.3 0 0 0.5
s 1248 864 1328 864 0 1 false
w 1328 1024 1328 864 0
v 1248 928 1248 864 0 2 4 1.6 1.6 0 0.35000000000000003
g 1248 928 1248 944 0
f 1088 1520 1120 1520 32 0.8 2
r 1120 1552 1120 1600 0 3.3
g 1120 1600 1120 1616 0
w 1120 1536 1120 1552 1
w 1120 1552 1056 1584 0
r 1040 1520 1088 1520 0 680
a 944 1520 1040 1520 9 3.2 0.1 1000000 0 0 100000
w 944 1584 944 1536 2
r 896 1440 896 1504 0 325000
r 896 1504 896 1552 0 5000
g 896 1552 896 1568 0
w 944 1504 896 1504 2
R 896 1440 896 1408 0 0 40 3.3 0 0 0.5
f 1936 912 1984 912 32 1.5 0.25
r 1984 928 2032 928 0 0.05
r 1872 1072 1872 1104 0 2
f 1936 1056 1872 1056 32 1.5 0.25
r 944 1584 1056 1584 0 5000
r 2080 816 2080 848 0 5000
r 2080 848 2080 896 0 5000
155 1680 1200 1728 1200 0 0
155 1808 1200 1888 1200 0 0
w 1776 1200 1808 1200 0
w 1728 880 1728 896 0
w 1936 1056 1936 1152 0
d 2080 992 1984 992 2 default
w 1904 1200 1936 1200 0
w 1568 1040 1568 1184 0
w 2032 1200 2064 1200 0
155 1936 1200 1984 1200 0 0
155 2064 1200 2112 1200 0 0
w 2064 1152 2064 1232 0
w 1936 1152 1936 1232 0
w 1808 1152 1808 1232 0
w 1680 1152 1680 1232 0
150 2320 1504 2224 1504 2 2 0 3.3
w 2320 1488 2320 1520 0
150 1728 912 1872 912 2 2 0 3.3
w 1680 1152 1808 1152 0
w 1808 1152 1936 1152 0
w 1936 1152 2064 1152 0
w 2064 1152 2176 1152 0
150 1568 1200 1648 1200 2 2 0 3.3
w 1648 1200 1680 1200 0
w 2320 992 2320 1136 0
f 1648 1520 1568 1520 32 0.6 3
g 1568 1536 1568 1552 0
r 1568 1504 1568 1456 0 10000
R 1568 1456 1568 1424 0 0 40 3.3 0 0 0.5
w 1568 1216 1536 1216 0
w 1536 1504 1568 1504 0
r 2224 1504 2160 1504 0 270
c 2160 1504 2160 1552 0 0.000001 0.001
g 2160 1552 2160 1568 0
w 2128 1504 2160 1504 0
w 1152 1328 1360 1328 0
w 1456 1424 1456 1616 0
34 GaP-SuperBrightGreen-2.3v 0 9.32e-11 0.042 4.71 0
162 1216 1392 1216 1472 2 GaP-SuperBrightGreen-2.3v 0 1 0 0.02
162 1184 1392 1184 1472 2 GaP-SuperBrightGreen-2.3v 0 1 0 0.02
162 1152 1392 1152 1472 2 GaP-SuperBrightGreen-2.3v 0 1 0 0.02
162 1120 1392 1120 1472 2 GaP-SuperBrightGreen-2.3v 0 1 0 0.02
w 1360 1360 1184 1360 0
w 1360 1392 1216 1392 0
w 1776 1200 1648 1296 0
w 1456 1296 1648 1296 0
w 1904 1200 1760 1328 0
w 1456 1328 1680 1328 0
w 2032 1200 1856 1360 0
w 1456 1360 1712 1360 0
w 2160 1200 1984 1392 0
w 1456 1392 1744 1392 0
w 1120 1472 1120 1504 0
162 1680 1408 1680 1472 2 default-led 1 1 0 0.02
162 1712 1408 1712 1472 2 default-led 1 1 0 0.02
162 1744 1408 1744 1472 2 default-led 1 1 0 0.02
w 1648 1296 1648 1408 0
w 1680 1328 1680 1408 0
w 1712 1360 1712 1408 0
w 1744 1392 1744 1408 0
w 2032 1616 2032 1520 0
w 1648 1472 1680 1472 0
w 1680 1472 1712 1472 0
w 1712 1472 1744 1472 0
w 1648 1472 1648 1520 0
w 1536 1504 1536 1216 0
w 1456 1616 2032 1616 0
w 1680 1328 1760 1328 0
w 1712 1360 1856 1360 0
w 1744 1392 1984 1392 0
w 1120 1472 1152 1472 0
w 1152 1472 1184 1472 0
w 1184 1472 1216 1472 0
w 1184 1360 1184 1392 0
w 1152 1328 1152 1392 0
w 1360 1296 1120 1296 0
w 1120 1296 1120 1392 0
o 12 64 0 4099 5 0.00009765625 0 2 12 3
o 25 64 0 4099 5 0.00009765625 0 2 25 3
o 40 4 0 4099 0.0000762939453125 0.00009765625 1 2 40 3
o 22 4 0 4099 2.5 0.00009765625 1 2 22 3
o 28 4 0 4099 5 0.00009765625 1 2 28 3
o 92 1 0 4099 0.0000762939453125 0.00009765625 2 2 92 3
o 90 1 0 4099 0.0000762939453125 0.00009765625 2 2 90 3