Overview:

This project uses and ESP32 and 16 buttons to create a tiny stenographic keyboard that outputs words efficiently based on most used English words stored in an external flash.

Description:

We store hundreds of common english words in the I2C EEPROM, and program ESP32 to handle switch debouncing.

Features:

• 18 switches, 3 LED indicators, and common switch layout

• ESP32S2 for good interrupt support and large GPIO pin count

• Extreme Responsiveness / Soft Realtime through FreeRTOS

• Arduino Core for Compatibility

• Supports over 400 possible words!

Featured Code Snippets:

void ARDUINO_ISR_ATTR ButtonsBase::buttonInterrupt(void *pinMetadata) {

   auto &pinMetadataRef = *static_cast<PinMetadata *>(pinMetadata);

   detachInterrupt(pinMetadataRef.pin);

   auto &self = *pinMetadataRef.buttons;

   if (pinMetadataRef.falling) {

       self.pressedPins->set(pinMetadataRef.pos);

   } else {

       self.toDelete->set(pinMetadataRef.pos);

       if (*self.pressedPins == *self.toDelete) {

           timerStop(self.timer);

           self.alarmed = false;

           self.sendBitset(&self);

           self.pressedPins->reset();

           self.toDelete->reset();

       } else {

           timerRestart(self.timer);

           if (!self.alarmed) {

               self.alarmed = true;

               timerStart(self.timer);

           }

       }

   }

   pinMetadataRef.falling = !pinMetadataRef.falling;

   esp_timer_start_once(pinMetadataRef.timer, BOUNCE_DELAY);

}

template <size_t size>

void ARDUINO_ISR_ATTR Bitset<size>::set_impl(volatile void *num, std::size_t pos, bool value) {

   auto &numRef = *static_cast<volatile num_t *>(num);

   using oneType = std::remove_extent_t<num_t>;

   auto const state = taskENTER_CRITICAL_FROM_ISR();

   if constexpr (words == 0) {

       if (value) {

           numRef |= oneType{1U} << pos;

       } else {

           numRef &= ~(oneType{1U} << pos);

       }

   } else {

       auto const arrPos = pos / wordSize;

       auto const bitPos = pos % wordSize;

       auto &elemRef = numRef[arrPos];

       if (value) {

           elemRef |= oneType{1U} << bitPos;

       } else {

           elemRef &= ~(oneType{1U} << bitPos);

       }

   }

   taskEXIT_CRITICAL_FROM_ISR(state);

}

template <std::ranges::sized_range Range, std::size_t size>

requires PinDataType<size>

void ARDUINO_ISR_ATTR Buttons<Range, size>::sendBitset(void *selfPtr) {

   auto &self = *static_cast<Buttons<Range, size>*>(selfPtr);

   auto xHigherPriorityTaskWoken = pdFALSE;

   xQueueSendFromISR(self.xButtonsQueue, self.pressedPins, &xHigherPriorityTaskWoken);

   portYIELD_FROM_ISR(xHigherPriorityTaskWoken);

}

template <std::ranges::sized_range Range, std::size_t size>

requires PinDataType<size>

void Keyboard<Range, size>::vTaskConsumer(void *pvParameters) {

   auto &self = *static_cast<Keyboard<Range, size>*>(pvParameters);

   auto recievedBitset = Bitset<size>{};

   for (;;) {

       if (xQueueReceive(self.xBitsetQueue, &recievedBitset, portMAX_DELAY) == pdPASS) {

           auto const retrievedString = self.getStringFromBitset(recievedBitset.getSTDBitset());

           if (retrievedString) {

               self.keyboard.print(retrievedString);

           }

       }

   }

}

Completed Schematic with USB-C, 18 Switches, 3 LEDs, 3.3V LDO, EEPROM, and ESP32