Add button tests

This is implemented by connecting the DTR pin of the serial device to the BTN_UP pin of the watch.

Also, make it possible to flash different applications with the Makefile.

Resolves #4

firmware/jlink.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+# Copyright (C) 2020  Max Regan
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+set -e
+
+DEVICE_TYPE=$1
+APP_BIN="$2"
+ADDR=0x8000000
+
+FLASH_SCRIPT="\
+exitonerror 1
+h
+r
+loadbin ${APP_BIN} ${ADDR}
+g
+q"
+
+flash_script="$(mktemp)"
+echo "$FLASH_SCRIPT" > "$flash_script"
+
+JLinkExe -device "$DEVICE_TYPE" -if SWD \
+       -speed auto -autoconnect 1 -CommanderScript "$flash_script"
+
+rm "$flash_script"