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spi_butterfly - parport-to-butterfly adapter driver | ||
=================================================== | ||
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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. | ||
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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. | ||
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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). | ||
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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 | ||
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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. | ||
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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 | ||
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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: | ||
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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 | ||
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IRQ = J402.PF4 = pin 10/S6,ACK | ||
GND = J402.GND(P2) = pin 25/GND | ||
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