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Added parabolic musings 10/16/19, see below

…On using motioneye video clients on Pi Zeros & Raspbian over a BATMAN-adv Ad-Hoc network

link: motioneyeos
link: motioneye Daemon
link: Pi Zero W Tx/Rx data sheet:
link: BATMAN Open Mesh

This implementation of motioneye is running on Raspbian Buster (opposed to motioneyeos).

Calculating Mesh Effectiveness w/ Python:
Please take a look at dBmLoss.py- the idea here is one should be able to estimate the maximum plausible distance between mesh nodes before setting anything up. It can be run with no arguments-

python3 dBmLoss.py

…with no arguments, it should use default values (Tx = 20 dBm, Rx = |-40| dBm) to print this:

you can add (default) Rx Tx arguments using the following syntax: python3 dBmLoss.py 20 40 python3 dBmLoss.py <Rx> <Tx>

57.74559999999994 ft = max. mesh node spacing, @ Rx = 40 Tx = 20

_Regarding the Pi:
_The Pi Zero uses an onboard BCM43143 wifi module. See above for the data sheet. We can expect around a ~19 dBm Tx signal from a BCM43143 if we are optimistic. Unfortunately, “usable” Rx gain is unclear in the context of the Pi.

Added 10/16/19:
Notes on generating an accurate parabolic antenna shape with FreeCAD’s Python CLI:

For whatever reason, (likely my own ignorance) I have been having trouble generating an accurate parabolic dish shape in Fusion 360 (AFAICT, Autodesk is literally drenching Fusion 360 in funds right now, I feel obligated to at least try). Bezier, spline, etc curves are not suitable!
If you are not familiar with FreeCAD, the general approach- geometry is formed through fully constraining sketches and objects- is quite different from Sketchup / Tinkercad / Inventor / etc, as most proprietary 3d software does the “constraining” of your drawings behind the scenes. From this perspective, you can see how the following script never actually defines or changes the curve / depth of the parabola; all we need to do is change how much curve to include. A wide, shallow dish can be made by only using the very bottom of the curve, or a deep / narrow dish by including more of the ever steepening parabolic shape.

import Part, math

musings derived from:

https://forum.freecadweb.org/viewtopic.php?t=4430

thinking about units here:

tu = FreeCAD.Units.parseQuantity

def mm(value): return tu(’{} mm’.format(value))

rs = mm(1.9) thicken = -(rs / mm(15))

defer to scale during fitting / fillet elsewhere

m=App.Matrix() m.rotateY(math.radians(-90))

create a parabola with the symmetry axis (0,0,1)

parabola=Part.Parabola() parabola.transform(m)

get only the right part of the curve

edge=parabola.toShape(0,rs) pt=parabola.value(rs) line=Part.makeLine(pt,App.Vector(0,0,pt.z)) wire=Part.Wire([edge,line]) shell=wire.revolve(App.Vector(0,0,0),App.Vector(0,0,1),360)

make a solid

solid=Part.Solid(shell)

apply a thickness

thick=solid.makeThickness([solid.Faces[1]],thicken,0.001) Part.show(thick)

Gui.SendMsgToActiveView(“ViewFit”)

"""

Fill screen:

Gui.SendMsgToActiveView(“ViewFit”)

Remove Part in default env:

App.getDocument(“Unnamed1”).removeObject(“Shape”) """

FWIW, here is my Python implimentation of a Tx/Rx “Free Space” distance calulator-
dBmLoss.py:

from math import log10 from sys import argv '''

estimate free space dBm attenuation:

…using wfi module BCM43143:

Tx = 19~20 dBm Rx = not clear how low we can go here

d = distance Tx —> Rx f = frequency c = attenuation constant: meters / MHz = -27.55; see here for more info: https://en.wikipedia.org/wiki/Free-space_path_loss '''

f = 2400 # MHz c = 27.55 # RF attenuation constant (in meters / MHz)

def_Tx = 20 # expected dBm transmit def_Rx = 40 # (absolute value) of negative dBm thesh

def logdBm(num): return 20 * log10(num)

def maxDist(Rx, Tx): dBm = 0 d = .1 # meters! while dBm < Tx + Rx: dBm = logdBm(d) + logdBm(f) - Tx - Rx + c d += .1 # meters! return d

Why not use this with arguments Tx + Rx from shell if we want:

def useargs(): use = bool try: if len(argv) == 3: use = True elif len(argv) == 1: print(‘\n\nyou can add (default) Rx Tx arguments using the following syntax: \n \ python3 dBmLoss.py 20 40 \n \ python3 dBmLoss.py <Rx> <Tx> \ \n’) use = False else: print(‘you must use both Rx & Tx arguments or no arguments’) raise SystemExit except: print(‘you must use both Rx & Tx arguments or no arguments’) raise SystemExit return use

def main():

if useargs() == True: arg = [int(argv[1]), int(argv[2])] else: arg = [def_Rx, def_Tx]

print(str(‘\n ’ + str(maxDist(arg[0], arg[1])*3.281) + \ ’ ft = max. mesh node spacing, @ \n’ + \ ’ Rx = ’ + str(arg[0]) + ‘\n’ + \ ’ Tx = ’ + str(arg[1])))

main()

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