Resources https://www.raspberrypi.org/documentation/configuration/uart.md

The Raspberry Pi has a 1-wire bus which can be enabled on GPIO4.

Using the USB Port in slave device mode RPi boards that don't include a USB hub IC, such as the RPi Model A and RPi Compute Module, can take advantage of the USB OTG feature. https://gist.github.com/gbaman/50b6cca61dd1c3f88f41

Oldest to newest Model B Revision 1.0 (256MB) PCB says: "Raspberry Pi (c) 2011" Model B Revision 1.0 (ECN0001) (256MB) Model B Revision 2.0 (256MB) Model A Revision 2.0 (256MB) PCB says: "Raspberry Pi (c)2011.12" Model B Revision 2.0 (512MB) PCB says: "Raspberry Pi (c)2011.12" Model B+ Revision 1.0 (512MB) PCB says: "Raspberry Pi Model B+ V1.2" Compute Module Revision 1.0 (512MB) Model A+ Revision 1.0 (512MB) […]

The RPi doesn't have an audio input, you need to use I2S via the IO pins or a USB sound card. Sound Cards For The Raspberry Pi Wolfson Pi Audio Card USB Sound Card Resources kb9mwr.blogspot.co.uk  

Use /proc/cpuinfo to read the One-Time-Programmable hardware version number value burned into the SoC at manufacture (along with the unique serial number, etc). 000f means the Rev 2.0 board with 512M memory.  Some of those had 5 burnt in by mistake, but firmware interprets that as f

  The Raspberry Pi SoC (System on Chip) is a Broadcom BCM2835. The ARM This contains an ARM1176JZFS (ARM11), with floating point, running at 700Mhz (over clocking to 800MHz is often OK if needed). Software needs to be compiled for ARMv6 to be used with the Raspberry Pi. The GPU Videocore 4 GPU. Capable of BluRay quality playback, using H.264 at 40MBits/s. Fast 3D core accessed using the supplied OpenGL […]

The minimum size SD card you can use for Rasbian is 2GB, but it is recommended to get a 4GB SD card or above. Card Speed A Class 4 card, which is the minimum recommended has an average read/write speed of 4 MB/sec.  If you spend a little extra and buy a Class 10 card, […]