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Old Dec 02, 2012, 10:15 PM
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raspberry pi comes to life

Keeping the camera mount in its laser painter form wasn't an option, because there wasn't enough room to store every gadget. Now, the tripod blind nut & more of the wood had to go. 3 circuit boards have to go on it.

There were a number of options. Wifi ended up having too many dropouts to be used in any feedback loop, but would have to be used when communicating with a tablet.

So all the intense vision processing had to be done on the camera mount, wired to the cameras. The camera mount required an access point to communicate with a tablet for the user interface.

In the old days, this would have required an FPGA or DSP with custom software. Nowadays, a 1Ghz linux board computer can do it very cheaply. The computational requirement meant the STM32F407 was completely out of this project. A common webcam + board computer was the cheapest method.

Once the SD card is flashed & the right pins are soldered to 5V, GND, & UART, the raspberry pi runs exactly like any other board computer you know & love. It has a single serial console, network interface, & USB. USB is your only realistic path to the hardware world.


Steps to bringing it up:
log in as

user: pi
passwd: raspberry

enable root login:
sudo passwd root

step up to 1Ghz & reduce video RAM:
raspi-config

/boot/config.txt contains the settings

enable static ethernet:

vi /etc/network/interfaces

change

iface eth0 inet dhcp

to

iface eth0 inet static
address 10.0.0.11
netmask 255.255.255.0
gateway 10.0.0.9

disable swap file:
vi /etc/init.d/dphys-swapfile

fix slow ssh login:
vi /etc/hosts


Maximum CPU speed:

echo userspace > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo 1000000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed



Download cross compiler from:

https://github.com/raspberrypi/tools

So far, it needs 0.5A when idle. That requires a modern USB charger wall wart, a PC power supply, or a really big, heavy, bench supply.
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Last edited by Jack Crossfire; Dec 05, 2012 at 05:02 PM.
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