From ba1820777ca0624754ae326c24ada3a90b7d484b Mon Sep 17 00:00:00 2001
From: MCUdude <hansibull@gmail.com>
Date: Sat, 11 Apr 2020 16:37:56 +0200
Subject: [PATCH] Add support for 4, 2 and 1 MHz external clock Closes #129

---
 README.md      |  3 ++
 avr/boards.txt | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/README.md b/README.md
index da4682c6d..a17abed4c 100644
--- a/README.md
+++ b/README.md
@@ -66,8 +66,11 @@ You might experience upload issues when using the internal oscillator. It's fact
 | 11.0592 MHz | External crystal/oscillator | Great clock for UART communication with no error              |
 | 8 MHz       | External crystal/oscillator | Common clock when working with 3.3V                           |
 | 7.3728 MHz  | External crystal/oscillator | Great clock for UART communication with no error              |
+| 4 MHz       | External crystal/oscillator |                                                               |
 | 3.6864 MHz  | External crystal/oscillator | Great clock for UART communication with no error              |
+| 2 MHz       | External crystal/oscillator |                                                               |
 | 1.8432 MHz  | External crystal/oscillator | Great clock for UART communication with no error              |
+| 1 MHz       | External crystal/oscillator |                                                               |
 | 8 MHz       | Internal oscillator         | Might cause UART upload issues. See comment above this table  |
 | 4 MHz       | Internal oscillator         | Derived from the 8 MHz internal oscillator                    |
 | 2 MHz       | Internal oscillator         | Derived from the 8 MHz internal oscillator                    |
diff --git a/avr/boards.txt b/avr/boards.txt
index 949e81e76..8f6308dec 100644
--- a/avr/boards.txt
+++ b/avr/boards.txt
@@ -172,6 +172,13 @@ menu.bootloader=Bootloader
 328.menu.clock.7_3728MHz_external.build.clock_speed={build.f_cpu}
 328.menu.clock.7_3728MHz_external.build.f_cpu=7372800L
 
+328.menu.clock.4MHz_external=External 4 MHz
+328.menu.clock.4MHz_external.upload.speed=9600
+328.menu.clock.4MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+328.menu.clock.4MHz_external.build.clkpr=
+328.menu.clock.4MHz_external.build.clock_speed={build.f_cpu}
+328.menu.clock.4MHz_external.build.f_cpu=4000000L
+
 328.menu.clock.3_6864MHz_external=External 3.6864 MHz
 328.menu.clock.3_6864MHz_external.upload.speed=115200
 328.menu.clock.3_6864MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
@@ -179,6 +186,13 @@ menu.bootloader=Bootloader
 328.menu.clock.3_6864MHz_external.build.clock_speed={build.f_cpu}
 328.menu.clock.3_6864MHz_external.build.f_cpu=3686400L
 
+328.menu.clock.2MHz_external=External 2 MHz
+328.menu.clock.2MHz_external.upload.speed=9600
+328.menu.clock.2MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+328.menu.clock.2MHz_external.build.clkpr=
+328.menu.clock.2MHz_external.build.clock_speed={build.f_cpu}
+328.menu.clock.2MHz_external.build.f_cpu=2000000L
+
 328.menu.clock.1_8432MHz_external=External 1.8432 MHz
 328.menu.clock.1_8432MHz_external.upload.speed=115200
 328.menu.clock.1_8432MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
@@ -186,6 +200,13 @@ menu.bootloader=Bootloader
 328.menu.clock.1_8432MHz_external.build.clock_speed={build.f_cpu}
 328.menu.clock.1_8432MHz_external.build.f_cpu=1843200L
 
+328.menu.clock.1MHz_external=External 1 MHz
+328.menu.clock.1MHz_external.upload.speed=9600
+328.menu.clock.1MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+328.menu.clock.1MHz_external.build.clkpr=
+328.menu.clock.1MHz_external.build.clock_speed={build.f_cpu}
+328.menu.clock.1MHz_external.build.f_cpu=1000000L
+
 328.menu.clock.8MHz_internal=Internal 8 MHz
 328.menu.clock.8MHz_internal.upload.speed=38400
 328.menu.clock.8MHz_internal.bootloader.low_fuses=0xe2
@@ -341,6 +362,13 @@ menu.bootloader=Bootloader
 168.menu.clock.7_3728MHz_external.build.clock_speed={build.f_cpu}
 168.menu.clock.7_3728MHz_external.build.f_cpu=7372800L
 
+168.menu.clock.4MHz_external=External 4 MHz
+168.menu.clock.4MHz_external.upload.speed=9600
+168.menu.clock.4MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+168.menu.clock.4MHz_external.build.clkpr=
+168.menu.clock.4MHz_external.build.clock_speed={build.f_cpu}
+168.menu.clock.4MHz_external.build.f_cpu=4000000L
+
 168.menu.clock.3_6864MHz_external=External 3.6864 MHz
 168.menu.clock.3_6864MHz_external.upload.speed=115200
 168.menu.clock.3_6864MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
@@ -348,6 +376,13 @@ menu.bootloader=Bootloader
 168.menu.clock.3_6864MHz_external.build.clock_speed={build.f_cpu}
 168.menu.clock.3_6864MHz_external.build.f_cpu=3686400L
 
+168.menu.clock.2MHz_external=External 2 MHz
+168.menu.clock.2MHz_external.upload.speed=9600
+168.menu.clock.2MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+168.menu.clock.2MHz_external.build.clkpr=
+168.menu.clock.2MHz_external.build.clock_speed={build.f_cpu}
+168.menu.clock.2MHz_external.build.f_cpu=2000000L
+
 168.menu.clock.1_8432MHz_external=External 1.8432 MHz
 168.menu.clock.1_8432MHz_external.upload.speed=115200
 168.menu.clock.1_8432MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
@@ -355,6 +390,13 @@ menu.bootloader=Bootloader
 168.menu.clock.1_8432MHz_external.build.clock_speed={build.f_cpu}
 168.menu.clock.1_8432MHz_external.build.f_cpu=1843200L
 
+168.menu.clock.1MHz_external=External 1 MHz
+168.menu.clock.1MHz_external.upload.speed=9600
+168.menu.clock.1MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+168.menu.clock.1MHz_external.build.clkpr=
+168.menu.clock.1MHz_external.build.clock_speed={build.f_cpu}
+168.menu.clock.1MHz_external.build.f_cpu=1000000L
+
 168.menu.clock.8MHz_internal=Internal 8 MHz
 168.menu.clock.8MHz_internal.upload.speed=38400
 168.menu.clock.8MHz_internal.bootloader.low_fuses=0xe2
@@ -509,6 +551,13 @@ menu.bootloader=Bootloader
 88.menu.clock.7_3728MHz_external.build.clock_speed={build.f_cpu}
 88.menu.clock.7_3728MHz_external.build.f_cpu=7372800L
 
+88.menu.clock.4MHz_external=External 4 MHz
+88.menu.clock.4MHz_external.upload.speed=9600
+88.menu.clock.4MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+88.menu.clock.4MHz_external.build.clkpr=
+88.menu.clock.4MHz_external.build.clock_speed={build.f_cpu}
+88.menu.clock.4MHz_external.build.f_cpu=4000000L
+
 88.menu.clock.3_6864MHz_external=External 3.6864 MHz
 88.menu.clock.3_6864MHz_external.upload.speed=115200
 88.menu.clock.3_6864MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
@@ -516,6 +565,13 @@ menu.bootloader=Bootloader
 88.menu.clock.3_6864MHz_external.build.clock_speed={build.f_cpu}
 88.menu.clock.3_6864MHz_external.build.f_cpu=3686400L
 
+88.menu.clock.2MHz_external=External 2 MHz
+88.menu.clock.2MHz_external.upload.speed=9600
+88.menu.clock.2MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+88.menu.clock.2MHz_external.build.clkpr=
+88.menu.clock.2MHz_external.build.clock_speed={build.f_cpu}
+88.menu.clock.2MHz_external.build.f_cpu=2000000L
+
 88.menu.clock.1_8432MHz_external=External 1.8432 MHz
 88.menu.clock.1_8432MHz_external.upload.speed=115200
 88.menu.clock.1_8432MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
@@ -523,6 +579,13 @@ menu.bootloader=Bootloader
 88.menu.clock.1_8432MHz_external.build.clock_speed={build.f_cpu}
 88.menu.clock.1_8432MHz_external.build.f_cpu=1843200L
 
+88.menu.clock.1MHz_external=External 1 MHz
+88.menu.clock.1MHz_external.upload.speed=9600
+88.menu.clock.1MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+88.menu.clock.1MHz_external.build.clkpr=
+88.menu.clock.1MHz_external.build.clock_speed={build.f_cpu}
+88.menu.clock.1MHz_external.build.f_cpu=1000000L
+
 88.menu.clock.8MHz_internal=Internal 8 MHz
 88.menu.clock.8MHz_internal.upload.speed=38400
 88.menu.clock.8MHz_internal.bootloader.low_fuses=0xe2
@@ -664,18 +727,36 @@ menu.bootloader=Bootloader
 48.menu.clock.7_3728MHz_external.build.clkpr=
 48.menu.clock.7_3728MHz_external.build.f_cpu=7372800L
 
+48.menu.clock.4MHz_external=External 4 MHz
+48.menu.clock.4MHz_external.upload.speed=9600
+48.menu.clock.4MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+48.menu.clock.4MHz_external.build.clkpr=
+48.menu.clock.4MHz_external.build.f_cpu=4000000L
+
 48.menu.clock.3_6864MHz_external=External 3.6864 MHz
 48.menu.clock.3_6864MHz_external.upload.speed=115200
 48.menu.clock.3_6864MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
 48.menu.clock.3_6864MHz_external.build.clkpr=
 48.menu.clock.3_6864MHz_external.build.f_cpu=3686400L
 
+48.menu.clock.2MHz_external=External 2 MHz
+48.menu.clock.2MHz_external.upload.speed=9600
+48.menu.clock.2MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+48.menu.clock.2MHz_external.build.clkpr=
+48.menu.clock.2MHz_external.build.f_cpu=2000000L
+
 48.menu.clock.1_8432MHz_external=External 1.8432 MHz
 48.menu.clock.1_8432MHz_external.upload.speed=115200
 48.menu.clock.1_8432MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
 48.menu.clock.1_8432MHz_external.build.clkpr=
 48.menu.clock.1_8432MHz_external.build.f_cpu=1843200L
 
+48.menu.clock.1MHz_external=External 1 MHz
+48.menu.clock.1MHz_external.upload.speed=9600
+48.menu.clock.1MHz_external.bootloader.low_fuses=0b1111{bootloader.cksel_bits}
+48.menu.clock.1MHz_external.build.clkpr=
+48.menu.clock.1MHz_external.build.f_cpu=1000000L
+
 48.menu.clock.8MHz_internal=Internal 8 MHz
 48.menu.clock.8MHz_internal.upload.speed=38400
 48.menu.clock.8MHz_internal.bootloader.low_fuses=0xe2
@@ -803,18 +884,36 @@ menu.bootloader=Bootloader
 8.menu.clock.7_3728MHz_external.bootloader.ckopt_bit=0
 8.menu.clock.7_3728MHz_external.build.f_cpu=7372800L
 
+8.menu.clock.4MHz_external=External 4 MHz
+8.menu.clock.4MHz_external.upload.speed=9600
+8.menu.clock.4MHz_external.bootloader.sut_cksel_bits=111111
+8.menu.clock.4MHz_external.bootloader.ckopt_bit=0
+8.menu.clock.4MHz_external.build.f_cpu=4000000L
+
 8.menu.clock.3_6864MHz_external=External 3.6864 MHz
 8.menu.clock.3_6864MHz_external.upload.speed=115200
 8.menu.clock.3_6864MHz_external.bootloader.sut_cksel_bits=111111
 8.menu.clock.3_6864MHz_external.bootloader.ckopt_bit=0
 8.menu.clock.3_6864MHz_external.build.f_cpu=3686400L
 
+8.menu.clock.2MHz_external=External 2 MHz
+8.menu.clock.2MHz_external.upload.speed=9600
+8.menu.clock.2MHz_external.bootloader.sut_cksel_bits=111111
+8.menu.clock.2MHz_external.bootloader.ckopt_bit=0
+8.menu.clock.2MHz_external.build.f_cpu=2000000L
+
 8.menu.clock.1_8432MHz_external=External 1.8432 MHz
 8.menu.clock.1_8432MHz_external.upload.speed=115200
 8.menu.clock.1_8432MHz_external.bootloader.sut_cksel_bits=111111
 8.menu.clock.1_8432MHz_external.bootloader.ckopt_bit=0
 8.menu.clock.1_8432MHz_external.build.f_cpu=1843200L
 
+8.menu.clock.1MHz_external=External 1 MHz
+8.menu.clock.1MHz_external.upload.speed=9600
+8.menu.clock.1MHz_external.bootloader.sut_cksel_bits=111111
+8.menu.clock.1MHz_external.bootloader.ckopt_bit=0
+8.menu.clock.1MHz_external.build.f_cpu=1000000L
+
 8.menu.clock.8MHz_internal=Internal 8 MHz
 8.menu.clock.8MHz_internal.upload.speed=38400
 8.menu.clock.8MHz_internal.bootloader.sut_cksel_bits=100100