From 9c4bf0ac4aed4ab315f27bfa5d2f54b0dd931138 Mon Sep 17 00:00:00 2001
From: Joel Challis <git@zvecr.com>
Date: Thu, 2 Apr 2020 22:23:57 +0100
Subject: [PATCH] Initial support for ATtiny85 (#8632)

* Initial support for ATtiny85

* Update mcu selection
---
 quantum/config_common.h          |  3 +++
 quantum/mcu_selection.mk         | 15 +++++++++++++++
 tmk_core/common/avr/bootloader.c |  2 +-
 tmk_core/common/avr/timer.c      | 21 ++++++++++++++-------
 4 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/quantum/config_common.h b/quantum/config_common.h
index 4cfd74b0fe..9861c86780 100644
--- a/quantum/config_common.h
+++ b/quantum/config_common.h
@@ -63,6 +63,9 @@
 #        define PINB_ADDRESS 0x3
 #        define PINC_ADDRESS 0x6
 #        define PIND_ADDRESS 0x9
+#    elif defined(__AVR_ATtiny85__)
+#        define ADDRESS_BASE 0x10
+#        define PINB_ADDRESS 0x6
 #    else
 #        error "Pins are not defined"
 #    endif
diff --git a/quantum/mcu_selection.mk b/quantum/mcu_selection.mk
index ef7e8ae75d..33de162bb1 100644
--- a/quantum/mcu_selection.mk
+++ b/quantum/mcu_selection.mk
@@ -287,3 +287,18 @@ ifneq (,$(filter $(MCU),atmega328p))
   NO_UART ?= yes
   NO_SUSPEND_POWER_DOWN ?= yes
 endif
+
+ifneq (,$(filter $(MCU),attiny85))
+  PROTOCOL = VUSB
+
+  # Processor frequency.
+  #     This will define a symbol, F_CPU, in all source code files equal to the
+  #     processor frequency in Hz. You can then use this symbol in your source code to
+  #     calculate timings. Do NOT tack on a 'UL' at the end, this will be done
+  #     automatically to create a 32-bit value in your source code.
+  F_CPU ?= 16500000
+
+  # unsupported features for now
+  NO_UART ?= yes
+  NO_SUSPEND_POWER_DOWN ?= yes
+endif
diff --git a/tmk_core/common/avr/bootloader.c b/tmk_core/common/avr/bootloader.c
index ca9746f327..32f69ae8b4 100644
--- a/tmk_core/common/avr/bootloader.c
+++ b/tmk_core/common/avr/bootloader.c
@@ -247,7 +247,7 @@ void bootloader_jump(void) {
 
 #else  // Assume remaining boards are DFU, even if the flag isn't set
 
-#    if !(defined(__AVR_ATmega32A__) || defined(__AVR_ATmega328P__))  // no USB - maybe BOOTLOADER_BOOTLOADHID instead though?
+#    if !(defined(__AVR_ATmega32A__) || defined(__AVR_ATmega328P__) || defined(__AVR_ATtiny85__))  // no USB - maybe BOOTLOADER_BOOTLOADHID instead though?
     UDCON  = 1;
     USBCON = (1 << FRZCLK);  // disable USB
     UCSR1B = 0;
diff --git a/tmk_core/common/avr/timer.c b/tmk_core/common/avr/timer.c
index 88fa1dfa65..c2e6c6e081 100644
--- a/tmk_core/common/avr/timer.c
+++ b/tmk_core/common/avr/timer.c
@@ -45,19 +45,26 @@ void timer_init(void) {
 #    error "Timer prescaler value is not valid"
 #endif
 
-#ifndef __AVR_ATmega32A__
+#if defined(__AVR_ATmega32A__)
+    // Timer0 CTC mode
+    TCCR0 = _BV(WGM01) | prescaler;
+
+    OCR0  = TIMER_RAW_TOP;
+    TIMSK = _BV(OCIE0);
+#elif defined(__AVR_ATtiny85__)
+    // Timer0 CTC mode
+    TCCR0A = _BV(WGM01);
+    TCCR0B = prescaler;
+
+    OCR0A = TIMER_RAW_TOP;
+    TIMSK = _BV(OCIE0A);
+#else
     // Timer0 CTC mode
     TCCR0A = _BV(WGM01);
     TCCR0B = prescaler;
 
     OCR0A  = TIMER_RAW_TOP;
     TIMSK0 = _BV(OCIE0A);
-#else
-    // Timer0 CTC mode
-    TCCR0 = _BV(WGM01) | prescaler;
-
-    OCR0  = TIMER_RAW_TOP;
-    TIMSK = _BV(OCIE0);
 #endif
 }