From 6fd216e83d2c213ca53669c86d08316fb87b9385 Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Sun, 22 Jan 2023 17:46:16 +0100
Subject: [PATCH] avr: added routines to read/write EEPROM.

---
 avr/utils.asm | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/avr/utils.asm b/avr/utils.asm
index 24c4ea1..61db65a 100644
--- a/avr/utils.asm
+++ b/avr/utils.asm
@@ -93,4 +93,54 @@ Utils_IncrementCounter32:
 
 
 
+; ***************************************************************************
+; Utils_ReadEeprom
+;
+; Read a byte from EEPROM (see example in ATtiny24/44/84 manual p.19).
+;
+; IN:
+; - X: EEPROM Address to read from
+; OUT:
+; - R16: byte read
+; MODIFIED REGISTERS: R16
+
+Utils_ReadEeprom:
+  sbic EECR, EEPE          ; wait for previous write to complete (if any)
+    rjmp Utils_ReadEeprom
+  out EEARH, xh            ; set EEPROM address
+  out EEARL, xl
+  sbi EECR, EERE           ; start EEPROM read by writing EERE
+  in r16, EEDR             ; read data from data register
+  ret
+
+
+
+; ***************************************************************************
+; Utils_WriteEeprom
+;
+; Write a byte to EEPROM (see example in ATtiny24/44/84 manual p.18).
+;
+; IN:
+; - R16: byte to write
+; - X: EEPROM Address to read from
+; OUT:
+; - nothing
+; MODIFIED REGISTERS: R17
+
+Utils_WriteEeprom:
+  sbic EECR, EEPE          ; wait for previous write to complete (if any)
+    rjmp Utils_WriteEeprom
+  ldi r17, (0<<EEPM1) | (0<<EEPM0) ; set programming mode
+  out EECR, r17
+  out EEARH, xh                    ; set EEPROM address
+  out EEARL, xl
+  out EEDR,  r16                   ; write data to data register
+  sbi EECR, EEMPE                  ; write logical one to EEMPE
+  sbi EECR, EEPE                   ; start EEPROM write by setting EEPE
+  ret
+
+
+
+
+