butterfly.rst (3339B)
1=================================================== 2spi_butterfly - parport-to-butterfly adapter driver 3=================================================== 4 5This is a hardware and software project that includes building and using 6a parallel port adapter cable, together with an "AVR Butterfly" to run 7firmware for user interfacing and/or sensors. A Butterfly is a $US20 8battery powered card with an AVR microcontroller and lots of goodies: 9sensors, LCD, flash, toggle stick, and more. You can use AVR-GCC to 10develop firmware for this, and flash it using this adapter cable. 11 12You can make this adapter from an old printer cable and solder things 13directly to the Butterfly. Or (if you have the parts and skills) you 14can come up with something fancier, providing circuit protection to the 15Butterfly and the printer port, or with a better power supply than two 16signal pins from the printer port. Or for that matter, you can use 17similar cables to talk to many AVR boards, even a breadboard. 18 19This is more powerful than "ISP programming" cables since it lets kernel 20SPI protocol drivers interact with the AVR, and could even let the AVR 21issue interrupts to them. Later, your protocol driver should work 22easily with a "real SPI controller", instead of this bitbanger. 23 24 25The first cable connections will hook Linux up to one SPI bus, with the 26AVR and a DataFlash chip; and to the AVR reset line. This is all you 27need to reflash the firmware, and the pins are the standard Atmel "ISP" 28connector pins (used also on non-Butterfly AVR boards). On the parport 29side this is like "sp12" programming cables. 30 31 ====== ============= =================== 32 Signal Butterfly Parport (DB-25) 33 ====== ============= =================== 34 SCK J403.PB1/SCK pin 2/D0 35 RESET J403.nRST pin 3/D1 36 VCC J403.VCC_EXT pin 8/D6 37 MOSI J403.PB2/MOSI pin 9/D7 38 MISO J403.PB3/MISO pin 11/S7,nBUSY 39 GND J403.GND pin 23/GND 40 ====== ============= =================== 41 42Then to let Linux master that bus to talk to the DataFlash chip, you must 43(a) flash new firmware that disables SPI (set PRR.2, and disable pullups 44by clearing PORTB.[0-3]); (b) configure the mtd_dataflash driver; and 45(c) cable in the chipselect. 46 47 ====== ============ =================== 48 Signal Butterfly Parport (DB-25) 49 ====== ============ =================== 50 VCC J400.VCC_EXT pin 7/D5 51 SELECT J400.PB0/nSS pin 17/C3,nSELECT 52 GND J400.GND pin 24/GND 53 ====== ============ =================== 54 55Or you could flash firmware making the AVR into an SPI slave (keeping the 56DataFlash in reset) and tweak the spi_butterfly driver to make it bind to 57the driver for your custom SPI-based protocol. 58 59The "USI" controller, using J405, can also be used for a second SPI bus. 60That would let you talk to the AVR using custom SPI-with-USI firmware, 61while letting either Linux or the AVR use the DataFlash. There are plenty 62of spare parport pins to wire this one up, such as: 63 64 ====== ============= =================== 65 Signal Butterfly Parport (DB-25) 66 ====== ============= =================== 67 SCK J403.PE4/USCK pin 5/D3 68 MOSI J403.PE5/DI pin 6/D4 69 MISO J403.PE6/DO pin 12/S5,nPAPEROUT 70 GND J403.GND pin 22/GND 71 72 IRQ J402.PF4 pin 10/S6,ACK 73 GND J402.GND(P2) pin 25/GND 74 ====== ============= ===================