Tuesday 31 January 2017

Trident Guidance System

So the military cannot fire a trident Missile from a submarine towards a target satisfactorily.

I wonder if it is possible to write a guidance program using a Raspberry Pi. The inputs would have to be the current GPS Location (2 fields) and the target GPS Location plus altitude (3 Fields).

I suppose, not being an expert, that from these input values the program would have to calculate the distance to the target allowing for curvature of the earth, and therefore how high the missile would have to go - the apogee.

Another thing that would be needed is a compass to determine the direction of flight.  This possibly can be determined by calculations on two successive GPS readings?  And knowing the orientation of the Missile. How would you know this? That way you would know which side rockets to fire or rudders to control to point it in the right direction.

How many inputs/outputs would you need? If it's anything like my RC-Car then two outputs for each of the north/south rudders and two for each of the east/west rudders, and appropriate inputs to give feedback on the positions of these rudders. Then there is the throttle control for the rocket motors, however that works.

A good start.



Tuesday 17 January 2017

Raspberry Pi Differences

The Problem that instigated this investigation was that I bought two Aqprox Wireless-N Nano USB Wireless adapters and could not get one to work on my test-rig Raspberry Pi. After doing all the usual swapping around, the conclusion was that there were differences in the R-Pi's that the adapter would not work on one, but was quite happy on the other.

As found from: http://www.raspberrypi-spy.co.uk/2012/09/checking-your-raspberry-pi-board-version/



pi@raspberrypi:~ $ cat /proc/cpuinfo               *** Model B  Revision 2
processor       : 0
model name      : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS        : 2.00
Features        : half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb76
CPU revision    : 7

Hardware        : BCM2708
Revision        : 000f
Serial          : 000000002dab1189
pi@raspberrypi:~ $

works with Ralink Ok

Last login: Mon Jan 16 09:17:15 2017               *** Model B revision 1
pi@raspberrypi:~ $ cat /proc/cpuinfo
processor       : 0
model name      : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS        : 697.95
Features        : half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb76
CPU revision    : 7

Hardware        : BCM2708
Revision        : 0002
Serial          : 000000004cb2f7c8
pi@raspberrypi:~ $

Fails with Ralink  ??? why?


http://elinux.org/RPi_HardwareHistory

www.element14.com/community/docs/DOC-78141/l/identifying-your-model-of-raspberry-pi
- Sorry, that's member only access.

http://www.raspberrypi-spy.co.uk/2012/09/raspberry-pi-board-revisions/

and for completeness:
en.wikipedia.org/wiki/Raspberry_Pi


From the elinux web site I ascertained that the unit that didn't work was a Model B Revision 1. It does not have any mounting holes. The one that does work is a Model B revision 2.  So I will label the procinfo outputs above.

Further research needed to determine why it doesn't work, but meanwhile I'll have to use the Zyxel wireless dongle

2017-01-18 Response from R-Pi forum:
The RPi B rev 1 has polyfuses in the power circuits of each USB port. The fuses limit the power too much for WIFI and so only low current devices such as keyboard and mouse will work. The fuses were removed in rev2 and power is directly connected to the 5V supply.
On my rev1 boards I removed the fuses and soldered wires across the pads to make them more like the Rev2 board.

So now we know.