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Diffstat (limited to 'Documentation/spi')
| -rw-r--r-- | Documentation/spi/butterfly | 57 |
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diff --git a/Documentation/spi/butterfly b/Documentation/spi/butterfly new file mode 100644 index 00000000000..a2e8c8d90e3 --- /dev/null +++ b/Documentation/spi/butterfly @@ -0,0 +1,57 @@ +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 + |