| spi_butterfly - parport-to-butterfly adapter driver |
| =================================================== |
| |
| This is a hardware and software project that includes building and using |
| a parallel port adapter cable, together with an "AVR Butterfly" to run |
| firmware for user interfacing and/or sensors. A Butterfly is a $US20 |
| battery powered card with an AVR microcontroller and lots of goodies: |
| sensors, LCD, flash, toggle stick, and more. You can use AVR-GCC to |
| develop firmware for this, and flash it using this adapter cable. |
| |
| You can make this adapter from an old printer cable and solder things |
| directly to the Butterfly. Or (if you have the parts and skills) you |
| can come up with something fancier, providing ciruit protection to the |
| Butterfly and the printer port, or with a better power supply than two |
| signal pins from the printer port. |
| |
| |
| The first cable connections will hook Linux up to one SPI bus, with the |
| AVR and a DataFlash chip; and to the AVR reset line. This is all you |
| need to reflash the firmware, and the pins are the standard Atmel "ISP" |
| connector pins (used also on non-Butterfly AVR boards). |
| |
| Signal Butterfly Parport (DB-25) |
| ------ --------- --------------- |
| SCK = J403.PB1/SCK = pin 2/D0 |
| RESET = J403.nRST = pin 3/D1 |
| VCC = J403.VCC_EXT = pin 8/D6 |
| MOSI = J403.PB2/MOSI = pin 9/D7 |
| MISO = J403.PB3/MISO = pin 11/S7,nBUSY |
| GND = J403.GND = pin 23/GND |
| |
| Then to let Linux master that bus to talk to the DataFlash chip, you must |
| (a) flash new firmware that disables SPI (set PRR.2, and disable pullups |
| by clearing PORTB.[0-3]); (b) configure the mtd_dataflash driver; and |
| (c) cable in the chipselect. |
| |
| Signal Butterfly Parport (DB-25) |
| ------ --------- --------------- |
| VCC = J400.VCC_EXT = pin 7/D5 |
| SELECT = J400.PB0/nSS = pin 17/C3,nSELECT |
| GND = J400.GND = pin 24/GND |
| |
| The "USI" controller, using J405, can be used for a second SPI bus. That |
| would let you talk to the AVR over SPI, running firmware that makes it act |
| as an SPI slave, while letting either Linux or the AVR use the DataFlash. |
| There are plenty of spare parport pins to wire this one up, such as: |
| |
| Signal Butterfly Parport (DB-25) |
| ------ --------- --------------- |
| SCK = J403.PE4/USCK = pin 5/D3 |
| MOSI = J403.PE5/DI = pin 6/D4 |
| MISO = J403.PE6/DO = pin 12/S5,nPAPEROUT |
| GND = J403.GND = pin 22/GND |
| |
| IRQ = J402.PF4 = pin 10/S6,ACK |
| GND = J402.GND(P2) = pin 25/GND |
| |