checkin

README

@@ -0,0 +1,31 @@
+# Why are there two microcontrollers?
+
+Cost and ease of development. 
+
+Both ESP8266 and ATTINY(2/4/8)5 modules can be had for around \$1 each, and
+there are retail programming jigs available. I have a kid now and don't want to
+spend my time making a programming board.
+
+The ESP8266 alone cannot really wake from multiple sources and know trap the
+source of the interrupt- there is only one pin that can wake up the micro from
+deep sleep, and that same pin needs to be used if you want to use the RTC as a
+wake source. Sure, you could use an OR-gate and also wire each source to a GPIO,
+but you might miss the source by the time the ESP wakes up to check the pins.
+
+Hence, the ATTINY is used to capture the wakeup and inform the ESP8266, who does
+the heavy lifting.
+
+## What about ESP32?
+
+The cheapest modules I can find at the time of writing are around \$3.50 apiece,
+and they can be power hungry (spikes up to 750mA compared to 400mA, from what I
+read).
+
+## What about ESP32-S2?
+
+They appear promising and are only \$2 per module on Digikey at the time of
+writing, however they are not supported by platformio yet.
+
+## What about ...?
+
+I probably wasn't aware that it exists.

ecad/IotButtonV0/IotButtonV0-cache.lib

@@ -0,0 +1,292 @@
+EESchema-LIBRARY Version 2.4
+#encoding utf-8
+#
+# Connector_Generic_MountingPin_Conn_01x05_MountingPin
+#
+DEF Connector_Generic_MountingPin_Conn_01x05_MountingPin J 0 40 Y N 1 F N
+F0 "J" 0 300 50 H V C CNN
+F1 "Connector_Generic_MountingPin_Conn_01x05_MountingPin" 50 -300 50 H V L CNN
+F2 "" 0 0 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+$FPLIST
+ Connector*:*_1x??-1MP*
+$ENDFPLIST
+DRAW
+T 0 0 -265 15 0 1 1 Mounting Normal 0 C C
+S -50 -195 0 -205 1 1 6 N
+S -50 -95 0 -105 1 1 6 N
+S -50 5 0 -5 1 1 6 N
+S -50 105 0 95 1 1 6 N
+S -50 205 0 195 1 1 6 N
+S -50 250 50 -250 1 1 10 f
+P 2 1 1 6 -40 -280 40 -280 N
+X Pin_1 1 -200 200 150 R 50 50 1 1 P
+X Pin_2 2 -200 100 150 R 50 50 1 1 P
+X Pin_3 3 -200 0 150 R 50 50 1 1 P
+X Pin_4 4 -200 -100 150 R 50 50 1 1 P
+X Pin_5 5 -200 -200 150 R 50 50 1 1 P
+X MountPin MP 0 -400 120 U 50 50 1 1 P
+ENDDRAW
+ENDDEF
+#
+# Device_Battery_Cell
+#
+DEF Device_Battery_Cell BT 0 0 N N 1 F N
+F0 "BT" 100 100 50 H V L CNN
+F1 "Device_Battery_Cell" 100 0 50 H V L CNN
+F2 "" 0 60 50 V I C CNN
+F3 "" 0 60 50 V I C CNN
+DRAW
+S -90 70 90 60 0 1 0 F
+S -62 47 58 27 0 1 0 F
+P 2 0 1 0 0 30 0 0 N
+P 2 0 1 0 0 70 0 100 N
+P 2 0 1 10 20 135 60 135 N
+P 2 0 1 10 40 155 40 115 N
+X + 1 0 200 100 D 50 50 1 1 P
+X - 2 0 -100 100 U 50 50 1 1 P
+ENDDRAW
+ENDDEF
+#
+# Device_C_Small
+#
+DEF Device_C_Small C 0 10 N N 1 F N
+F0 "C" 10 70 50 H V L CNN
+F1 "Device_C_Small" 10 -80 50 H V L CNN
+F2 "" 0 0 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+$FPLIST
+ C_*
+$ENDFPLIST
+DRAW
+P 2 0 1 13 -60 -20 60 -20 N
+P 2 0 1 12 -60 20 60 20 N
+X ~ 1 0 100 80 D 50 50 1 1 P
+X ~ 2 0 -100 80 U 50 50 1 1 P
+ENDDRAW
+ENDDEF
+#
+# Device_LED_ARGB
+#
+DEF Device_LED_ARGB D 0 0 Y N 1 F N
+F0 "D" 0 370 50 H V C CNN
+F1 "Device_LED_ARGB" 0 -350 50 H V C CNN
+F2 "" 0 -50 50 H I C CNN
+F3 "" 0 -50 50 H I C CNN
+$FPLIST
+ LED*
+ LED_SMD:*
+ LED_THT:*
+$ENDFPLIST
+DRAW
+C 80 0 10 0 1 0 F
+T 0 -75 -250 50 0 0 0 B Normal 0 C C
+T 0 -75 -50 50 0 0 0 G Normal 0 C C
+T 0 -75 150 50 0 0 0 R Normal 0 C C
+S 50 250 50 250 0 1 0 N
+S 110 330 -110 -300 0 1 10 f
+P 2 0 1 0 -100 -200 50 -200 N
+P 2 0 1 8 -50 -150 -50 -250 N
+P 2 0 1 8 -50 50 -50 -50 N
+P 2 0 1 8 -50 250 -50 150 N
+P 2 0 1 0 50 200 -100 200 N
+P 2 0 1 0 100 0 -100 0 N
+P 4 0 1 0 50 -200 80 -200 80 200 50 200 N
+P 4 0 1 8 50 -150 50 -250 -50 -200 50 -150 N
+P 4 0 1 8 50 50 50 -50 -50 0 50 50 N
+P 4 0 1 8 50 250 50 150 -50 200 50 250 N
+P 5 0 1 0 -40 -150 20 -90 -10 -90 20 -90 20 -120 N
+P 5 0 1 0 -40 50 20 110 -10 110 20 110 20 80 N
+P 5 0 1 0 -40 250 20 310 -10 310 20 310 20 280 N
+P 5 0 1 0 0 -150 60 -90 30 -90 60 -90 60 -120 N
+P 5 0 1 0 0 50 60 110 30 110 60 110 60 80 N
+P 5 0 1 0 0 250 60 310 30 310 60 310 60 280 N
+X A 1 200 0 100 L 50 50 1 1 P
+X RK 2 -200 200 100 R 50 50 1 1 P
+X GK 3 -200 0 100 R 50 50 1 1 P
+X BK 4 -200 -200 100 R 50 50 1 1 P
+ENDDRAW
+ENDDEF
+#
+# Device_R_Small_US
+#
+DEF Device_R_Small_US R 0 10 N N 1 F N
+F0 "R" 30 20 50 H V L CNN
+F1 "Device_R_Small_US" 30 -40 50 H V L CNN
+F2 "" 0 0 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+$FPLIST
+ R_*
+$ENDFPLIST
+DRAW
+P 5 1 1 0 0 0 40 -15 0 -30 -40 -45 0 -60 N
+P 5 1 1 0 0 60 40 45 0 30 -40 15 0 0 N
+X ~ 1 0 100 40 D 50 50 1 1 P
+X ~ 2 0 -100 40 U 50 50 1 1 P
+ENDDRAW
+ENDDEF
+#
+# Device_R_US
+#
+DEF Device_R_US R 0 0 N Y 1 F N
+F0 "R" 100 0 50 V V C CNN
+F1 "Device_R_US" -100 0 50 V V C CNN
+F2 "" 40 -10 50 V I C CNN
+F3 "" 0 0 50 H I C CNN
+$FPLIST
+ R_*
+$ENDFPLIST
+DRAW
+P 2 0 1 0 0 -90 0 -100 N
+P 2 0 1 0 0 90 0 100 N
+P 5 0 1 0 0 -30 40 -45 0 -60 -40 -75 0 -90 N
+P 5 0 1 0 0 30 40 15 0 0 -40 -15 0 -30 N
+P 5 0 1 0 0 90 40 75 0 60 -40 45 0 30 N
+X ~ 1 0 150 50 D 50 50 1 1 P
+X ~ 2 0 -150 50 U 50 50 1 1 P
+ENDDRAW
+ENDDEF
+#
+# MCU_Microchip_ATtiny_ATtiny85-20SU
+#
+DEF MCU_Microchip_ATtiny_ATtiny85-20SU U 0 20 Y Y 1 F N
+F0 "U" -500 550 50 H V L BNN
+F1 "MCU_Microchip_ATtiny_ATtiny85-20SU" 100 -550 50 H V L TNN
+F2 "Package_SO:SOIJ-8_5.3x5.3mm_P1.27mm" 0 0 50 H I C CIN
+F3 "" 0 0 50 H I C CNN
+ALIAS ATtiny25-20SU ATtiny45V-10SU ATtiny45-20SU ATtiny85V-10SU ATtiny85-20SU
+$FPLIST
+ SOIJ*5.3x5.3mm*P1.27mm*
+$ENDFPLIST
+DRAW
+S -500 -500 500 500 0 1 10 f
+X ~RESET~/PB5 1 600 -200 100 L 50 50 1 1 T
+X XTAL1/PB3 2 600 0 100 L 50 50 1 1 T
+X XTAL2/PB4 3 600 -100 100 L 50 50 1 1 T
+X GND 4 0 -600 100 U 50 50 1 1 W
+X AREF/PB0 5 600 300 100 L 50 50 1 1 T
+X PB1 6 600 200 100 L 50 50 1 1 T
+X PB2 7 600 100 100 L 50 50 1 1 T
+X VCC 8 0 600 100 D 50 50 1 1 W
+ENDDRAW
+ENDDEF
+#
+# RF_Module_ESP-12F
+#
+DEF RF_Module_ESP-12F U 0 20 Y Y 1 F N
+F0 "U" -500 750 50 H V L CNN
+F1 "RF_Module_ESP-12F" 500 750 50 H V R CNN
+F2 "RF_Module:ESP-12E" 0 0 50 H I C CNN
+F3 "" -350 100 50 H I C CNN
+ALIAS ESP-12F
+$FPLIST
+ ESP?12*
+$ENDFPLIST
+DRAW
+S -500 700 500 -600 0 1 10 f
+X ~RST 1 -600 600 100 R 50 50 1 1 I
+X MISO 10 -600 -100 100 R 50 50 1 1 B
+X GPIO9 11 -600 -200 100 R 50 50 1 1 B
+X GPIO10 12 -600 -300 100 R 50 50 1 1 B
+X MOSI 13 -600 -400 100 R 50 50 1 1 B
+X SCLK 14 -600 -500 100 R 50 50 1 1 B
+X GND 15 0 -700 100 U 50 50 1 1 W
+X GPIO15 16 600 -300 100 L 50 50 1 1 B
+X GPIO2 17 600 400 100 L 50 50 1 1 B
+X GPIO0 18 600 600 100 L 50 50 1 1 B
+X GPIO4 19 600 200 100 L 50 50 1 1 B
+X ADC 2 -600 200 100 R 50 50 1 1 I
+X GPIO5 20 600 100 100 L 50 50 1 1 B
+X GPIO3/RXD 21 600 300 100 L 50 50 1 1 B
+X GPIO1/TXD 22 600 500 100 L 50 50 1 1 B
+X EN 3 -600 400 100 R 50 50 1 1 I
+X GPIO16 4 600 -400 100 L 50 50 1 1 B
+X GPIO14 5 600 -200 100 L 50 50 1 1 B
+X GPIO12 6 600 0 100 L 50 50 1 1 B
+X GPIO13 7 600 -100 100 L 50 50 1 1 B
+X VCC 8 0 800 100 D 50 50 1 1 W
+X CS0 9 -600 0 100 R 50 50 1 1 I
+ENDDRAW
+ENDDEF
+#
+# Regulator_Linear_MCP1804x-3302xOT
+#
+DEF Regulator_Linear_MCP1804x-3302xOT U 0 10 Y Y 1 F N
+F0 "U" -250 225 50 H V C CNN
+F1 "Regulator_Linear_MCP1804x-3302xOT" 0 225 50 H V L CNN
+F2 "Package_TO_SOT_SMD:SOT-23-5" 0 300 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+ALIAS MCP1804x-2502xOT MCP1804x-3002xOT MCP1804x-3302xOT MCP1804x-5002xOT MCP1804x-A002xOT MCP1804x-C002xOT
+$FPLIST
+ SOT?23*
+$ENDFPLIST
+DRAW
+S -300 -200 300 175 0 1 10 f
+X VIN 1 -400 100 100 R 50 50 1 1 W
+X GND 2 0 -300 100 U 50 50 1 1 W
+X NC 3 300 0 100 L 50 50 1 1 N N
+X ~SHDN 4 -400 0 100 R 50 50 1 1 I
+X VOUT 5 400 100 100 L 50 50 1 1 w
+ENDDRAW
+ENDDEF
+#
+# Switch_SW_Push
+#
+DEF Switch_SW_Push SW 0 40 N N 1 F N
+F0 "SW" 50 100 50 H V L CNN
+F1 "Switch_SW_Push" 0 -60 50 H V C CNN
+F2 "" 0 200 50 H I C CNN
+F3 "" 0 200 50 H I C CNN
+DRAW
+C -80 0 20 0 1 0 N
+C 80 0 20 0 1 0 N
+P 2 0 1 0 0 50 0 120 N
+P 2 0 1 0 100 50 -100 50 N
+X 1 1 -200 0 100 R 50 50 0 1 P
+X 2 2 200 0 100 L 50 50 0 1 P
+ENDDRAW
+ENDDEF
+#
+# power_+BATT
+#
+DEF power_+BATT #PWR 0 0 Y Y 1 F P
+F0 "#PWR" 0 -150 50 H I C CNN
+F1 "power_+BATT" 0 140 50 H V C CNN
+F2 "" 0 0 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+DRAW
+P 2 0 1 0 -30 50 0 100 N
+P 2 0 1 0 0 0 0 100 N
+P 2 0 1 0 0 100 30 50 N
+X +BATT 1 0 0 0 U 50 50 1 1 W N
+ENDDRAW
+ENDDEF
+#
+# power_GND
+#
+DEF power_GND #PWR 0 0 Y Y 1 F P
+F0 "#PWR" 0 -250 50 H I C CNN
+F1 "power_GND" 0 -150 50 H V C CNN
+F2 "" 0 0 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+DRAW
+P 6 0 1 0 0 0 0 -50 50 -50 0 -100 -50 -50 0 -50 N
+X GND 1 0 0 0 D 50 50 1 1 W N
+ENDDRAW
+ENDDEF
+#
+# power_VCC
+#
+DEF power_VCC #PWR 0 0 Y Y 1 F P
+F0 "#PWR" 0 -150 50 H I C CNN
+F1 "power_VCC" 0 150 50 H V C CNN
+F2 "" 0 0 50 H I C CNN
+F3 "" 0 0 50 H I C CNN
+DRAW
+C 0 75 25 0 1 0 N
+P 2 0 1 0 0 0 0 50 N
+X VCC 1 0 0 0 U 50 50 1 1 W N
+ENDDRAW
+ENDDEF
+#
+#End Library

ecad/IotButtonV0/IotButtonV0.kicad_pcb

@@ -0,0 +1 @@
+(kicad_pcb (version 4) (host kicad "dummy file") )

ecad/IotButtonV0/IotButtonV0.pro

@@ -0,0 +1,33 @@
+update=22/05/2015 07:44:53
+version=1
+last_client=kicad
+[general]
+version=1
+RootSch=
+BoardNm=
+[pcbnew]
+version=1
+LastNetListRead=
+UseCmpFile=1
+PadDrill=0.600000000000
+PadDrillOvalY=0.600000000000
+PadSizeH=1.500000000000
+PadSizeV=1.500000000000
+PcbTextSizeV=1.500000000000
+PcbTextSizeH=1.500000000000
+PcbTextThickness=0.300000000000
+ModuleTextSizeV=1.000000000000
+ModuleTextSizeH=1.000000000000
+ModuleTextSizeThickness=0.150000000000
+SolderMaskClearance=0.000000000000
+SolderMaskMinWidth=0.000000000000
+DrawSegmentWidth=0.200000000000
+BoardOutlineThickness=0.100000000000
+ModuleOutlineThickness=0.150000000000
+[cvpcb]
+version=1
+NetIExt=net
+[eeschema]
+version=1
+LibDir=
+[eeschema/libraries]

ecad/IotButtonV0/_saved_IotButtonV0.pro

@@ -0,0 +1,33 @@
+update=22/05/2015 07:44:53
+version=1
+last_client=kicad
+[general]
+version=1
+RootSch=
+BoardNm=
+[pcbnew]
+version=1
+LastNetListRead=
+UseCmpFile=1
+PadDrill=0.600000000000
+PadDrillOvalY=0.600000000000
+PadSizeH=1.500000000000
+PadSizeV=1.500000000000
+PcbTextSizeV=1.500000000000
+PcbTextSizeH=1.500000000000
+PcbTextThickness=0.300000000000
+ModuleTextSizeV=1.000000000000
+ModuleTextSizeH=1.000000000000
+ModuleTextSizeThickness=0.150000000000
+SolderMaskClearance=0.000000000000
+SolderMaskMinWidth=0.000000000000
+DrawSegmentWidth=0.200000000000
+BoardOutlineThickness=0.100000000000
+ModuleOutlineThickness=0.150000000000
+[cvpcb]
+version=1
+NetIExt=net
+[eeschema]
+version=1
+LibDir=
+[eeschema/libraries]

firmware/lowpower_mcu/platformio.ini

@@ -16,7 +16,7 @@ platform = atmelavr
 framework = arduino
 board = attiny85
 upload_protocol = custom
-upload_port = /dev/ttyACM1
+upload_port = /dev/ttyACM0
 upload_speed = 19200
 upload_flags =
     -C

firmware/lowpower_mcu/src/AttinyDebounce.cpp

@@ -36,7 +36,6 @@ void AttinyDebounce::update(unsigned long millisNow) {
 
             break;
         case TRIGGERED:
-            // TODO: Debounce this part too
             if (!assertedNow) {
                 state = IDLE;
             }

firmware/lowpower_mcu/src/main.cpp

@@ -29,13 +29,14 @@ constexpr uint8_t BUTTON_PIN = 1; // Button press
 constexpr uint8_t RTC_PIN = 4; // RTC alarm (currently, from the ESP8266 RTC)
 constexpr uint8_t AUX_PIN = 5; // Another wakeup source. May be used for other sensors in the future.
 
-constexpr uint8_t DEBUG_LED = RTC_PIN;
+// constexpr uint8_t DEBUG_LED = RTC_PIN;
 
 constexpr unsigned long CMD_TIMEOUT_MILLIS = 1000; // After this period of with no commands, the device will sleep
 constexpr unsigned long WAKE_PULSE_MILLIS = 100; // Length of pulse sent to wake the main MCU
 constexpr unsigned long LONG_PRESS_MILLIS = 5000;
-constexpr unsigned long I2C_WATCHDOG_PERIOD_MILLIS = 2000; // If we don't get a request from the Main MCU in this time, just go to sleep.
+constexpr unsigned long I2C_WATCHDOG_PERIOD_MILLIS = 1000; // If we don't get a request from the Main MCU in this time, just go to sleep.
-constexpr unsigned long DEBOUNCE_MILLIS = 100;
+constexpr unsigned long DEBOUNCE_MILLIS = 1;
+constexpr unsigned long NO_WAKEUP_SRC_TIMEOUT_MILLIS = DEBOUNCE_MILLIS + 5;
 
 constexpr uint8_t I2C_DEVICE_ADDR = 0x4F; // Chosen arbitrarily
 
@@ -78,6 +79,7 @@ static unsigned long startWakeMillis, i2cWatchDogTime;
 static I2cReq i2c_cmd_byte;
 static volatile WakeSource wakeSource;
 static volatile unsigned long endButtonMillis;
+static unsigned long wakeupMillis = 0;
 
 static void i2cReceiveHook(int numBytes) {
     while (numBytes > 0) {
@@ -96,8 +98,6 @@ static void i2cRequestHook() {
     }
 }
 
-
-
 static void enablePinChangeInterrupt() {
     GIMSK |= _BV(PCIE);
     PCMSK |= _BV(BUTTON_PIN);
@@ -123,15 +123,15 @@ static void resetState() {
 void setup() {
     // Init pin states
     pinMode(MAIN_MCU_NRESET_PIN, OUTPUT);
-    pinMode(BUTTON_PIN, INPUT);
+    pinMode(BUTTON_PIN, INPUT_PULLUP);
-    pinMode(RTC_PIN, INPUT);
+    pinMode(RTC_PIN, INPUT_PULLUP);
-    pinMode(AUX_PIN, INPUT);
+    pinMode(AUX_PIN, INPUT_PULLUP);
-    pinMode(DEBUG_LED, OUTPUT);
+    // pinMode(DEBUG_LED, OUTPUT);
 
     // On first run, reset the main MCU to get in sync.
-    digitalWrite(MAIN_MCU_NRESET_PIN, HIGH);
-    delay(WAKE_PULSE_MILLIS);
     digitalWrite(MAIN_MCU_NRESET_PIN, LOW);
+    delay(WAKE_PULSE_MILLIS);
+    digitalWrite(MAIN_MCU_NRESET_PIN, HIGH);
 
     appState = AppState::SLEEP;
 
@@ -151,21 +151,19 @@ static void buttonCallback(int index) {
 }
 
 ISR(PCINT0_vect) {
-    unsigned long millisNow = millis();
+    ButtonDebounce.update(millis());
-    ButtonDebounce.update(millisNow);
 }
 
-
 void loop() {
-    unsigned long millisNow = millis();
+    ButtonDebounce.update(millis());
-    ButtonDebounce.update(millisNow);
 
     switch (appState) {
         case AppState::SLEEP:
             resetState();
-            //digitalWrite(DEBUG_LED, HIGH);
-            sleepUntilPinChange();
             // digitalWrite(DEBUG_LED, LOW);
+            sleepUntilPinChange();
+            wakeupMillis = millis();
+            // digitalWrite(DEBUG_LED, HIGH);
             appState = AppState::WATCHING_INPUT;
             break;
         case AppState::WATCHING_INPUT:
@@ -173,21 +171,24 @@ void loop() {
                 // Keep waiting. For example, waiting to see if long or short button press.
                 // TODO: Not yet implemented
             } else if (wakeSource == WakeSource::NONE) {
-                // appState = AppState::SLEEP;
+                if (millis() > wakeupMillis + NO_WAKEUP_SRC_TIMEOUT_MILLIS) {
+                    appState = AppState::SLEEP;
+                    break;
+                }
             } else {
                 // We know the wakeup source. Time to inform the main MCU.
                 appState = AppState::START_WAKE_MAIN_MCU;
             }
             break;
         case AppState::START_WAKE_MAIN_MCU:
-            digitalWrite(MAIN_MCU_NRESET_PIN, HIGH);
+            digitalWrite(MAIN_MCU_NRESET_PIN, LOW);
             startWakeMillis = millis();
             appState = AppState::WAKING_MAIN_MCU;
             break;
         case AppState::WAKING_MAIN_MCU:
             if (millis() > startWakeMillis + WAKE_PULSE_MILLIS) {
                 appState = AppState::WAITING_FOR_I2C;
-                digitalWrite(MAIN_MCU_NRESET_PIN, LOW);
+                digitalWrite(MAIN_MCU_NRESET_PIN, HIGH);
             }
             break;
         case AppState::WAITING_FOR_I2C:

firmware/main_mcu/.gitignore

@@ -0,0 +1,2 @@
+.pio
+src/config.h

firmware/main_mcu/include/README

@@ -0,0 +1,39 @@
+
+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

firmware/main_mcu/lib/README

@@ -0,0 +1,46 @@
+
+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

firmware/main_mcu/platformio.ini

@@ -0,0 +1,26 @@
+; 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]
+platform = espressif8266
+framework = arduino
+board = esp12e
+lib_deps = 
+	knolleary/PubSubClient@^2.8.0
+	bblanchon/ArduinoJson@^6.17.2
+upload_speed = 115200
+
+[env:button-release]
+
+[env:button-timing]
+build_flags = -D DEBUG_SKETCH_TIMING
+
+[env:button-debug]
+build_flags = -D DEBUG_SKETCH

firmware/main_mcu/src/main.cpp

@@ -0,0 +1,114 @@
+#include <Arduino.h>
+#include <ESP8266WiFi.h>
+#include <PubSubClient.h>
+#include <Wire.h>
+
+#include "config.h"
+#include "mqtt.h"
+#include "util.h"
+
+#define BTN_PIN D0
+#define RED_LED_PIN 4
+#define GREEN_LED_PIN 5
+#define BLUE_LED_PIN 12
+
+#define LONG_PRESS_MILLIS 1000
+
+static WiFiClient wifiClient;
+static PubSubClient mqttClient;
+
+void blink(int pin, int times, int onMillis, int offMillis) {
+    // for (int i = 0; i < times; i++) {
+    //     digitalWrite(pin, HIGH);
+    //     delay(onMillis);
+    //     digitalWrite(pin, LOW);
+    //     delay(offMillis);
+    // }
+}
+
+void fail(const char *message) {
+    PRINT(message);
+    blink(RED_LED_PIN, 3, 50, 50);
+    // TODO: go back to sleep
+}
+
+void success() {
+    blink(GREEN_LED_PIN, 1, 50, 0);
+}
+
+static void initConnection() {
+    initWifi(wifiClient);
+    initMqtt(mqttClient, wifiClient);
+}
+
+void handleShortButtonWakeup() {
+    initConnection();
+
+    if (!publishTriggerMessage(mqttClient, String("short_press"))) {
+        fail("failed to publish trigger message\n");
+    }
+
+    if (!publishBatteryMessage(mqttClient, 100)) {
+        fail("Failed to publish battery message\n");
+    }
+}
+
+void handleLongButtonWakeup() {
+    initConnection();
+    if (!publishHABatteryDiscoveryConfig(mqttClient)) {
+        fail("Failed to publish battery config\n");
+    }
+    if (!publishHATriggerDiscoveryConfig(mqttClient)) {
+        fail("Failed to publish trigger config\n");
+    }
+    if (!publishBatteryMessage(mqttClient, 100)) {
+        fail("Failed to publish trigger message\n");
+    }
+
+    success();
+}
+
+void setup() {
+    // Sample the input button ASAP.
+    // pinMode(BTN_PIN, INPUT);
+    // bool btn_value = digitalRead(BTN_PIN);
+
+    unsigned long startTimingMillis = millis();
+
+    pinMode(RED_LED_PIN, OUTPUT);
+    pinMode(BLUE_LED_PIN, OUTPUT);
+    pinMode(GREEN_LED_PIN, OUTPUT);
+
+#if defined(DEBUG_SKETCH) || defined(DEBUG_SKETCH_TIMING)
+    Serial.begin(9600);
+#endif
+
+    PRINTLN("\nBeginning setup\n");
+    PRINT("Device name:");
+    PRINTLN(getDeviceHumanName());
+
+    handleShortButtonWakeup();
+
+    digitalWrite(RED_LED_PIN, LOW);
+    digitalWrite(GREEN_LED_PIN, LOW);
+    digitalWrite(BLUE_LED_PIN, LOW);
+
+    // We've done our work- back to sleep.
+    PRINT("Going to sleep...\n");
+#if defined(DEBUG_SKETCH_TIMING)
+    unsigned long endTimeMillis = millis();
+    Serial.print("Ran for " + String(endTimeMillis - startTimingMillis) + " milliseconds\n");
+#endif
+
+    // Drain all of our pending requests
+    mqttClient.disconnect();
+    wifiClient.flush();
+    while (mqttClient.state() != -1) {
+        yield();
+    }
+    ESP.deepSleep(0, RFMode::RF_NO_CAL);
+}
+
+void loop() {
+
+}

firmware/main_mcu/src/mqtt.cpp

@@ -0,0 +1,146 @@
+#include "mqtt.h"
+
+#include <ArduinoJson.h>
+
+#include "config.h"
+#include "util.h"
+
+#define MAX_PACKET_SIZE    1024
+#define TIMEOUT_MILLIS     1000
+#define TRIGGER_KEY        "event"
+
+#define VALUE_TEMPLATE(key) ("{{ value_json." key " }}")
+
+// TODO: This should really be a class, this is kinda busted
+static bool isDone = true;
+
+void initMqtt(PubSubClient &mqttClient, WiFiClient &wifiClient) {
+    mqttClient.setServer(CONFIG_MQTT_SERVER, CONFIG_MQTT_SERVER_PORT);
+    mqttClient.setClient(wifiClient);
+    mqttClient.setBufferSize(MAX_PACKET_SIZE);
+    mqttClient.setCallback([](char *, unsigned char*, unsigned int){
+      PRINTLN("Message sent!");
+      isDone = true;
+    });
+
+    PRINT("Connecting to MQTT broker...");
+    while (!mqttClient.connected()) {
+        PRINT(".");
+        mqttClient.connect(getDeviceMachineName().c_str());
+    }
+    PRINTLN("\nConnected!");
+}
+
+static bool waitTilDone(PubSubClient &mqttClient) {
+    mqttClient.loop();
+    return true;
+    // unsigned long startTime = millis();
+
+    // do {
+    //     mqttClient.loop();
+    // } while (!isDone && startTime + TIMEOUT_MILLIS > millis());
+
+    // return isDone;
+}
+
+static String getHATriggerConfigTopic() {
+    return String(CONFIG_HOMEASSISTANT_MQTT_PREFIX "device_automation/") + getDeviceMachineName() + "/config";
+}
+
+static String getHASensorConfigTopic() {
+    return String(CONFIG_HOMEASSISTANT_MQTT_PREFIX "sensor/") + getDeviceMachineName() + "/config";
+}
+
+
+static String getButtonTopicBase(bool abbrev) {
+    if (abbrev) {
+        return String("~");
+    } else {
+        return String(CONFIG_BUTTON_EVENT_TOPIC_PREFIX) + getDeviceMachineName();
+    }
+}
+
+static String getButtonStateTopic(bool abbrev) {
+    return getButtonTopicBase(abbrev) + "/" CONFIG_BUTTON_STATE_TOPIC_NAME;
+}
+
+static String getButtonTriggerTopic(bool abbrev) {
+    return getButtonTopicBase(abbrev) + "/" CONFIG_BUTTON_TRIGGER_TOPIC_NAME;
+}
+
+static bool publishJsonDocument(PubSubClient &mqttClient, String topic, JsonDocument &message, bool retain) {
+    char str[MAX_PACKET_SIZE];
+    size_t len = serializeJson(message, str, MAX_PACKET_SIZE);
+    PRINT(topic);
+    PRINT(":");
+    PRINTLN(str);
+    isDone = false;
+    if (!mqttClient.publish(topic.c_str(), (uint8_t *) str, len, retain)) {
+        return false;
+    }
+    return waitTilDone(mqttClient);
+}
+
+static void addDeviceJson(JsonDocument &doc) {
+    JsonObject device = doc.createNestedObject("device");
+    device["name"] = getDeviceHumanName();
+    device["mf"] = "DIY"; // manufacturer
+    device["mdl"] = "IoT Button - ESP8266"; // model
+    device["sw"] = "1.0"; // sw_version
+
+    JsonArray ids = device.createNestedArray("ids");
+    ids.add(getDeviceId());
+}
+
+bool publishBatteryMessage(PubSubClient &mqttClient, int percentage) {
+    StaticJsonDocument<MAX_PACKET_SIZE> json;
+    json["battery"] = percentage;
+
+    isDone = false;
+    PRINTLN("Publishing battery message");
+    return publishJsonDocument(mqttClient, getButtonStateTopic(false), json, true);
+}
+
+bool publishTriggerMessage(PubSubClient &mqttClient, String message) {
+    isDone = false;
+    PRINTLN("Publishing trigger message");
+    if (!mqttClient.publish(getButtonTriggerTopic(false).c_str(), message.c_str(), false)) {
+        return false;
+    }
+    return waitTilDone(mqttClient);
+}
+
+bool publishHABatteryDiscoveryConfig(PubSubClient &mqttClient) {
+    StaticJsonDocument<MAX_PACKET_SIZE> json;
+    bool abbrev = true;
+
+    json["~"] = getButtonTopicBase(false);
+    json["stat_t"] = getButtonStateTopic(abbrev); // state_topic
+    json["val_tpl"] = VALUE_TEMPLATE("battery"); // state_value_template
+    json["uniq_id"] = getDeviceMachineName() + "-battery"; // unique_id
+    json["dev_cla"] = "battery"; // device_class
+    json["name"] = getDeviceHumanName() + ": Battery";
+
+    addDeviceJson(json);
+
+    PRINTLN("Publishing device sensor config");
+    return publishJsonDocument(mqttClient, getHASensorConfigTopic(), json, true);
+}
+
+bool publishHATriggerDiscoveryConfig(PubSubClient &mqttClient) {
+    StaticJsonDocument<MAX_PACKET_SIZE> json;
+    bool abbrev = true;
+
+    // json["name"] = getDeviceHumanName();
+    json["atype"] = "trigger"; // automation_type
+    json["type"] = "button_short_press";
+    json["stype"] = "button_1"; // subtype
+
+    json["~"] = getButtonTopicBase(false);
+    json["t"] = getButtonTriggerTopic(abbrev); // topic
+
+    addDeviceJson(json);
+
+    PRINTLN("Publishing device trigger discovery");
+    return publishJsonDocument(mqttClient, getHATriggerConfigTopic(), json, true);
+}

firmware/main_mcu/src/mqtt.h

@@ -0,0 +1,16 @@
+#ifndef __MQTT_H_
+#define __MQTT_H_
+
+#include <Arduino.h>
+#include <ESP8266WiFi.h>
+#include <PubSubClient.h>
+
+void initMqtt(PubSubClient& client, WiFiClient &wifiClient);
+
+bool publishHABatteryDiscoveryConfig(PubSubClient &client);
+bool publishHATriggerDiscoveryConfig(PubSubClient &client);
+
+bool publishTriggerMessage(PubSubClient &client, String message);
+bool publishBatteryMessage(PubSubClient &client, int percent);
+
+#endif // __MQTT_H_

firmware/main_mcu/src/util.cpp

@@ -0,0 +1,41 @@
+#include "util.h"
+
+#include "config.h"
+
+#define DEVICE_NAME_PREFIX "button-"
+
+#define PRINT_DELAY_MILLIS 500
+
+String getDeviceId() {
+    return String(ESP.getChipId(), HEX);
+}
+
+String getDeviceMachineName() {
+    return String(DEVICE_NAME_PREFIX) + getDeviceId();
+}
+
+String getDeviceHumanName() {
+    return "IoT Button (" + getDeviceId() + ")";
+}
+
+void initWifi(WiFiClient &wifi) {
+    PRINT("Connecting to WiFi using MAC: ");
+    PRINTLN(WiFi.macAddress());
+
+    WiFi.hostname(getDeviceMachineName().c_str());
+    WiFi.begin(CONFIG_SSID, CONFIG_PSK);
+    long last_time = millis();
+    while (WiFi.status() != WL_CONNECTED) {
+        yield();
+        long time = millis();
+        if (time >= last_time + PRINT_DELAY_MILLIS) {
+            PRINT(".");
+            last_time = time;
+        }
+    }
+
+    PRINTLN("\nConnected!");
+    PRINT("IP Address: ");
+    PRINTLN(WiFi.localIP());
+
+}

firmware/main_mcu/src/util.h

@@ -0,0 +1,21 @@
+#ifndef __UTIL_H_
+#define __UTIL_H_
+
+#include <Arduino.h>
+#include <ESP8266WiFi.h>
+
+#ifdef DEBUG_SKETCH
+#define PRINT(x) { Serial.print(x); } while (0)
+#define PRINTLN(x) { Serial.println(x); } while (0)
+#else
+#define PRINT(x)
+#define PRINTLN(x)
+#endif
+
+String getDeviceHumanName();
+String getDeviceMachineName();
+String getDeviceId();
+void initWifi(WiFiClient &wifi);
+
+
+#endif // __UTIL_H_

firmware/main_mcu/test/README

@@ -0,0 +1,11 @@
+
+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