2020-07-23 07:26:06 +10:00
|
|
|
# Writing to a AT28 EEPROM from a modern environment
|
|
|
|
|
|
|
|
|
|
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][avra] (will soon rewrite to Collapse OS' ASM)
|
|
|
|
|
* avrdude to send program to Arduino
|
|
|
|
|
|
|
|
|
|
## Schema
|
|
|
|
|
|
2020-08-22 10:25:06 +10:00
|
|
|
|
2020-07-23 07:26:06 +10:00
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
2020-07-29 05:18:26 +10:00
|
|
|
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.
|
|
|
|
|
|
2020-07-23 07:26:06 +10:00
|
|
|
## Software
|
|
|
|
|
|
|
|
|
|
The software in 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`.
|
|
|
|
|
|
|
|
|
|
[avra]: http://avra.sourceforge.net/
|
