Shepherding electrons

ATtiny85 Mario Challenge! The ATtiny85 microcontroller is a capable but compact AVR.  However with only 8K of program memory, 512 bytes of EEPROM, 512 of SRAM and only 8 pins (3 of which are dedicated to the usual suspects of Vcc, GND and RESET), it best suited to performing tasks where memory demands are not large, and only a few pins are required for interfacing.  

I wanted to setup programming my custom Atmega328p board over Bluetooth.  Some have used the connection pin to control the Reset pin of the AVR.  However I want to use Bluetooth constantly, and only trigger a reset upon receiving a specific string sequence.  This requires tweaking the bootloader, using Optiboot as a basis: (1) Change Baudrate to be mutually compatible with Bluebooth and AVR. (2) Set an EEPROM byte in the main application, which could be read (and written) in the Optiboot routine. Setting up Optiboot in the Atmel environment: - Setup a project as usual in Atmel Studio - Copy files over from github to the project folder: optiboot.c, pindefs.h, stk500.h and boot.h. EDIT: It seems there is an AtmelStudio folder already set up on github . Setting baud rate to be compatible with AVR and Bluetooth module: 57600 bps - Insert #define BAUD_RATE 57600 (as required) into optiboot.c . - Compile and link project with following settings: Compiler Mis...

A quick post of tragedy and triumph! Whilst breadboarding a new project with an Atmega328p chip (the heart of some of the Arduino ecosystem), I wanted to configure the AVR "fuses" (a desperately misleading term!) in order to use an external 16 MHz crystal, rather than the default internal 8 MHz oscillator.  This is straight forward and something I've done before.  Using the excellent fuse calculator , I wanted to get cracking and rushed in without double checking my fuse selection.  Big mistake!  I saw the option "external clock" (CKSEL=0000 SUT=00), and thought "great, that's it", also unselecting the CKDIV8 option (bit 7), generates the LOW fuse = 0xC0 and the HIGH fuse = 0xD9.  Two right mistakes here!  First of all the small one:  Selecting a box corresponds to setting the bit to '0', rather than '1', i.e. *unselecting/unticking* the CKDIV8 boxes will SET this bit as true (and divide the clock signal by 8).  It can't be...