http://www.homautomation.org/2013/09/21/433mhtz-rf-communication-between-arduino-and-raspberry-pi/433 send from arduino to pi

http://www.petervis.com/Raspberry_PI/Raspberry_Pi_GPIO_Header/Raspberry_Pi_GPIO_Header_Pin_Protection.htmlprotect gpio with diode

http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/gpio-pin-electrical-specificationsGPIO specs

https://www.fourtheye.org/armasm.shtml

https://wolfpaulus.com/journal/embedded/raspberrypi_boot

https://forums.raspberrypi.com/viewtopic.php?p=136266#p136266

https://pypi.org/project/RPi.GPIO/

https://devrandom.eu/?p=37

http://hertaville.com/2012/09/28/development-environment-raspberry-pi-cross-compiler/ pi cross compiling with eclipse

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=72&t=26136&sid=5bacb99a1d1b5fb28705377bd15d2a8e pi bare metal forum

http://www.cl.cam.ac.uk/freshers/raspberrypi/tutorials/os/ Assembler course for beginners Cambridge university

http://raspberrypi.stackexchange.com/questions/2099/cambridge-university-raspberry-pi-operating-system-development-guide-questions more gpio addressing

http://www.raspberrypi.org/wp-content/uploads/2012/04/Raspberry-Pi-Schematics-R1.0.pdf circuit diagram

http://hertaville.com/2012/11/18/introduction-to-accessing-the-raspberry-pis-gpio-in-c/ raw gpio access

http://www.open.com.au/mikem/bcm2835/bcm2835_8h_source.html gpio addesses

http://www.raspberrypi-spy.co.uk/2012/06/simple-guide-to-the-rpi-gpio-header-and-pins/

$ as hello.asm # this will produce hello.o ELF object file $ ld -s -o hello a.out # this will produce hello executable

http://elinux.org/RPi_Low-level_peripherals gpio access in c RiscOS for Pi

http://www.apdl.co.uk/riscworld/volume9/issue2/firstbasic/chap04.htm beginning basic why risc os is better on pi

Linux is preemptive. you can't get round that, you're stuck with it stealing time. RISC OS is cooperative. If you want to take control, you can, just by not calling Wimp_Poll. Until you do, the Pi is yours. Of course if you have something else running, that won't get serviced until you do, but that's your decision, not the OS's

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=55&t=21648

https://www.riscosopen.org/forum/forums/4/topics/1437www.riscosopen.org/forum

http://www.svrsig.org/Beta.htm Manuals for RISC OS PI

http://foundation.riscos.com/Private/manuals/BASIC/ risc basic manual pdf

http://www.brucesmith.info/page14.htmlrisc os pi assembler book

http://www.riscosopen.org/news/articles/2012/11/05/official-release-of-risc-os-for-raspberry-pi-updated risc site pi image

http://downloads.raspberrypi.org/download.php?file=/images/riscos/riscos-2012-11-01-RC6/riscos-2012-11-01-RC6.zip Risc OS for pi