rpi – Page 2 – Kev's Development Toolbox

March 13, 2016

Raspberry Pi with Adafruit PiTFT screen

Just followed the steps in the tutorial to get the modified kernel installed with support for Adafruit’s PiTFT and it all worked great.

What I’m going to be using it for is to monitor status output from Direwolf as it receives/sends packets, so will be running it in text mode, and ideally I want to get Direwolf and LinBPQ starting together at boot, and outputing to the console.

I’ve almost got the startup script working (following suggestions here), but I might take a look to see if I can redirect output to one of the virtual terminals and have that output to the screen (like discussed here). Some more things to take a look at 🙂

fbtext – this might be useful too.

November 27, 2015

‘Resource busy’ when writing disk image using dd (OS X)

If you’re using dd to write disk images to sd card on OS X, if the card is already partitioned and the partition is mounted, you need to unmount the partition and not the whole sd card in order to write to it. See prior notes here, and solution to unmount the partition here on SO.

November 26, 2015

Raspberry Pi Zero for $5

The Raspberry Pi at just $35 I think is one of the most amazing things that has arrived in recent years, bringing low cost computing to schools and hobbyists.

Today however, the Raspberry Pi Foundation has announced the Pi Zero … for $5. Incredible!

If you’re in the UK and can pick up a copy of The MagPi magazine, there’s a free Pi Zero taped to the front cover…

August 26, 2015

Closer look at the registers on an ARM cpu

In my dabbling with ARM assembly so far (my most recent achievement was completing my simple sorting algorithm – last update here), I had picked up that there’s 16 general purpose 32bit registers for holding either values or addresses, R0 through to R15, but paying a closer look I realized some of these have specific purposes, and or uses by convention.

R0: function argument or result

R1-R3: function args

R4-12: general purpose

R13: SP – this is the stack pointer

R14: LR – Link Register – it’s holds the address to branch back to when you call BR LR

R15: PC – the Program Counter – address pointing to the current instruction being processed

More info in the great summary on ARM Assembly here, and also in the ARM11 tech ref here.