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