initial import

.hgignore

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+syntax: glob
+stage2/.pio
+stage2/.clang_complete
+stage2/.gcc-flags.json
+stage2/.ccls
+.*.sw?

docs/overview.txt

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+# pocket computer M4
+
+The PCM4 (pocket computer / M4) is a handheld computing device based
+around the Keyboard FeatherWing [1] and the Adafruit Feather M4 [2].
+The Feather M4 has 512K of flash memory, 192K of RAM, and 2M QSPI [3]
+flash.
+
+[1] https://www.tindie.com/products/arturo182/keyboard-featherwing-qwerty-keyboard-26-lcd/
+[2] https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51?view=all
+[3] https://github.com/adafruit/Adafruit_QSPI
+
+It will have a scheme-based operating system.
+
+## Feather M4 pinouts
+
++ A0: reserved
++ A1: reserved
++ A2: reserved for RFM9X CS
++ A3: reserved for RFM9X RST
++ A4: reserved for airlift ESPBUSY
++ A5: reserved for airlift ESPRESET
++ D4: reserved for RFM9X IRQ
++ D5: SD card CS
++ D6: STMPE CS
++ D9: LCD CS
++ D10: LCD DC
++ D11: neopixel
+
+## Peripherals
+
++ Display: 320x240 touchscreen
+  + ILI9341 LCD controller
+  + STMPE610 touchscreen
++ Keyboard: BB Q10 keyboard + 4x tactile buttons + 5-way switch
+  + I2C address: 0x1F
++ Planned: DS3231 RTC
+  + I2C address: 0x66
++ Planned: RFM95 LoRa featherwing
++ Planned: ESP32 airlift
++ Planned: ATECC608A cryptoprocessor
+
+## Boot sequence
+
+1. Stage 1: UF2 bootloader [4][5]
+2. Stage 2: base hardware environment
+   + hardware init
+   + I2C/SPI interface
+   + SD card
+   + RTC core
+   + scheme core
+3. Load boot.scm from SD card.
+
+Stretch goal:
++ Holding down the center button in the joystick should bring up a menu
+  of scheme files on the SD card, allowing the user to select the boot
+  code.
+
+Note that each stage is as minimal as possible, so stage 2 should
+contain just enough to load the operating system from boot.scm,
+which should contain the actual operating system.
+
+[4] https://learn.adafruit.com/adafruit-feather-m0-express-designed-for-circuit-python-circuitpython/uf2-bootloader-details
+[5] https://github.com/Microsoft/uf2

stage2/include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the usual convention is to give header files names that end with `.h'.
+It is most portable to use only letters, digits, dashes, and underscores in
+header file names, and at most one dot.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

stage2/lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into executable file.
+
+The source code of each library should be placed in a an own separate directory
+("lib/your_library_name/[here are source files]").
+
+For example, see a structure of the following two libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional, custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+and a contents of `src/main.c`:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+PlatformIO Library Dependency Finder will find automatically dependent
+libraries scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

stage2/platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:adafruit_feather_m4]
+platform = atmelsam
+board = adafruit_feather_m4
+framework = arduino
+
+; 28: Adafruit NeoPixel library
+; 83: Adafruit RTClib
+; 571: Adafruit ILI9341 library
+lib_deps =
+  - Wire
+  - SPI
+  - SD
+  - 28
+  - 83
+  - 571
+  - arturo182/BBQ10Keyboard

stage2/src/main.cc

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+#include <Adafruit_NeoPixel.h>
+
+
+Adafruit_NeoPixel pixels(1, 11, NEO_GRB + NEO_KHZ800);
+
+
+void
+init()
+{
+	Serial.begin(115200);
+}
+
+
+void
+main()
+{
+	static bool	on = false;
+	Serial.println("blink");
+
+	if (on) {
+		pixels.clear();
+	} else {
+		pixels.setPixelColor(0, pixels.color(0, 255, 0));
+	}
+	pixels.show();
+
+	delay(1000);
+}

stage2/test/README

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+
+This directory is intended for PlatformIO Unit Testing and project tests.
+
+Unit Testing is a software testing method by which individual units of
+source code, sets of one or more MCU program modules together with associated
+control data, usage procedures, and operating procedures, are tested to
+determine whether they are fit for use. Unit testing finds problems early
+in the development cycle.
+
+More information about PlatformIO Unit Testing:
+- https://docs.platformio.org/page/plus/unit-testing.html