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53 lines
1.6 KiB
Plaintext
53 lines
1.6 KiB
Plaintext
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# Writing to a AT28 EEPROM from a modern environment
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The Arduino Uno is a very popular platform based on the
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ATMega328p. While Collapse OS doesn't run on AVR MCUs (yet?),
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the Arduino can be a handy tool, which is why we have recipes
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for it here.
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In this recipe, we'll build ourselves an ad-hoc EEPROM holder
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which is designed to be driven from an Arduino Uno.
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# Gathering parts
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* An Arduino Uno
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* A AT28C64B
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* 2 '164 shift registers
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* Sockets, header pins, proto board, etc.
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* AVRA[1] (will soon rewrite to Collapse OS' ASM)
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* avrdude to send program to Arduino
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# Schema
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Schema is at img/at28wr.jpg.
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This is a rather simple circuit which uses 2 chained '164 shift
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register to drive the AT28 address pins and connects CE, WE, OE
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and the data pins directly to the Arduino. Pins have been chosen
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so that the protoboard can plug directly on the Arduino's right
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side (except for VCC, which needs to be wired).
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PD0 and PD1 are not used because they're used for the UART.
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AT28 selection pins are pulled up to avoid accidental writes due
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to their line floating before Arduino's initialization.
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I've put 1uf decoupling caps next to each IC.
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# Software
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The software in code/at28wr.asm listens to the UART and writes
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every byte it receives to the AT28, starting at address 0. It
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expects tty-escaped content (see /tools/ttysafe).
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After having written the byte, it re-reads it from the EEPROM
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and spits it back to the UART, tty-escaped.
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# Usage
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After you've build and sent your binary to the Arduino with
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"make send", you can send your (tty-safe!) content to your
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EEPROM using /tools/pingpong.
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[1]: http://avra.sourceforge.net/
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