adafruit_ble.cpp

#include "adafruit_ble.h"
#include <stdio.h>
#include <stdlib.h>
#include <alloca.h>
#include <util/delay.h>
#include <util/atomic.h>
#include "debug.h"
#include "pincontrol.h"
#include "timer.h"
#include "action_util.h"
#include "ringbuffer.hpp"
#include <string.h>

// These are the pin assignments for the 32u4 boards.
// You may define them to something else in your config.h
// if yours is wired up differently.
#ifndef AdafruitBleResetPin
#define AdafruitBleResetPin D4
#endif

#ifndef AdafruitBleCSPin
#define AdafruitBleCSPin    B4
#endif

#ifndef AdafruitBleIRQPin
#define AdafruitBleIRQPin   E6
#endif


#define SAMPLE_BATTERY
#define ConnectionUpdateInterval 1000 /* milliseconds */

static struct {
  bool is_connected;
  bool initialized;
  bool configured;

#define ProbedEvents 1
#define UsingEvents 2
  bool event_flags;

#ifdef SAMPLE_BATTERY
  uint16_t last_battery_update;
  uint32_t vbat;
#endif
  uint16_t last_connection_update;
} state;

// Commands are encoded using SDEP and sent via SPI
// https://github.com/adafruit/Adafruit_BluefruitLE_nRF51/blob/master/SDEP.md

#define SdepMaxPayload 16
struct sdep_msg {
  uint8_t type;
  uint8_t cmd_low;
  uint8_t cmd_high;
  struct __attribute__((packed)) {
    uint8_t len:7;
    uint8_t more:1;
  };
  uint8_t payload[SdepMaxPayload];
} __attribute__((packed));

// The recv latency is relatively high, so when we're hammering keys quickly,
// we want to avoid waiting for the responses in the matrix loop.  We maintain
// a short queue for that.  Since there is quite a lot of space overhead for
// the AT command representation wrapped up in SDEP, we queue the minimal
// information here.

enum queue_type {
  QTKeyReport, // 1-byte modifier + 6-byte key report
  QTConsumer,  // 16-bit key code
#ifdef MOUSE_ENABLE
  QTMouseMove, // 4-byte mouse report
#endif
};

struct queue_item {
  enum queue_type queue_type;
  uint16_t added;
  union __attribute__((packed)) {
    struct __attribute__((packed)) {
      uint8_t modifier;
      uint8_t keys[6];
    } key;

    uint16_t consumer;
    struct __attribute__((packed)) {
      int8_t x, y, scroll, pan;
      uint8_t buttons;
    } mousemove;
  };
};

// Items that we wish to send
static RingBuffer<queue_item, 40> send_buf;
// Pending response; while pending, we can't send any more requests.
// This records the time at which we sent the command for which we
// are expecting a response.
static RingBuffer<uint16_t, 2> resp_buf;

static bool process_queue_item(struct queue_item *item, uint16_t timeout);

enum sdep_type {
  SdepCommand = 0x10,
  SdepResponse = 0x20,
  SdepAlert = 0x40,
  SdepError = 0x80,
  SdepSlaveNotReady = 0xfe, // Try again later
  SdepSlaveOverflow = 0xff, // You read more data than is available
};

enum ble_cmd {
  BleInitialize = 0xbeef,
  BleAtWrapper = 0x0a00,
  BleUartTx = 0x0a01,
  BleUartRx = 0x0a02,
};

enum ble_system_event_bits {
  BleSystemConnected = 0,
  BleSystemDisconnected = 1,
  BleSystemUartRx = 8,
  BleSystemMidiRx = 10,
};

// The SDEP.md file says 2MHz but the web page and the sample driver
// both use 4MHz
#define SpiBusSpeed 4000000

#define SdepTimeout 150 /* milliseconds */
#define SdepShortTimeout 10 /* milliseconds */
#define SdepBackOff 25 /* microseconds */
#define BatteryUpdateInterval 10000 /* milliseconds */

static bool at_command(const char *cmd, char *resp, uint16_t resplen,
                       bool verbose, uint16_t timeout = SdepTimeout);
static bool at_command_P(const char *cmd, char *resp, uint16_t resplen,
                         bool verbose = false);

struct SPI_Settings {
  uint8_t spcr, spsr;
};

static struct SPI_Settings spi;

// Initialize 4Mhz MSBFIRST MODE0
void SPI_init(struct SPI_Settings *spi) {
  spi->spcr = _BV(SPE) | _BV(MSTR);
  spi->spsr = _BV(SPI2X);

  static_assert(SpiBusSpeed == F_CPU / 2, "hard coded at 4Mhz");

  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
    // Ensure that SS is OUTPUT High
    digitalWrite(B0, PinLevelHigh);
    pinMode(B0, PinDirectionOutput);

    SPCR |= _BV(MSTR);
    SPCR |= _BV(SPE);
    pinMode(B1 /* SCK */, PinDirectionOutput);
    pinMode(B2 /* MOSI */, PinDirectionOutput);
  }
}

static inline void SPI_begin(struct SPI_Settings*spi) {
  SPCR = spi->spcr;
  SPSR = spi->spsr;
}

static inline uint8_t SPI_TransferByte(uint8_t data) {
  SPDR = data;
  asm volatile("nop");
  while (!(SPSR & _BV(SPIF))) {
    ; // wait
  }
  return SPDR;
}

static inline void spi_send_bytes(const uint8_t *buf, uint8_t len) {
  if (len == 0) return;
  const uint8_t *end = buf + len;
  while (buf < end) {
    SPDR = *buf;
    while (!(SPSR & _BV(SPIF))) {
      ; // wait
    }
    ++buf;
  }
}

static inline uint16_t spi_read_byte(void) {
  return SPI_TransferByte(0x00 /* dummy */);
}

static inline void spi_recv_bytes(uint8_t *buf, uint8_t len) {
  const uint8_t *end = buf + len;
  if (len == 0) return;
  while (buf < end) {
    SPDR = 0; // write a dummy to initiate read
    while (!(SPSR & _BV(SPIF))) {
      ; // wait
    }
    *buf = SPDR;
    ++buf;
  }
}

#if 0
static void dump_pkt(const struct sdep_msg *msg) {
  print("pkt: type=");
  print_hex8(msg->type);
  print(" cmd=");
  print_hex8(msg->cmd_high);
  print_hex8(msg->cmd_low);
  print(" len=");
  print_hex8(msg->len);
  print(" more=");
  print_hex8(msg->more);
  print("\n");
}
#endif

// Send a single SDEP packet
static bool sdep_send_pkt(const struct sdep_msg *msg, uint16_t timeout) {
  SPI_begin(&spi);

  digitalWrite(AdafruitBleCSPin, PinLevelLow);
  uint16_t timerStart = timer_read();
  bool success = false;
  bool ready = false;

  do {
    ready = SPI_TransferByte(msg->type) != SdepSlaveNotReady;
    if (ready) {
      break;
    }

    // Release it and let it initialize
    digitalWrite(AdafruitBleCSPin, PinLevelHigh);
    _delay_us(SdepBackOff);
    digitalWrite(AdafruitBleCSPin, PinLevelLow);
  } while (timer_elapsed(timerStart) < timeout);

  if (ready) {
    // Slave is ready; send the rest of the packet
    spi_send_bytes(&msg->cmd_low,
                   sizeof(*msg) - (1 + sizeof(msg->payload)) + msg->len);
    success = true;
  }

  digitalWrite(AdafruitBleCSPin, PinLevelHigh);

  return success;
}

static inline void sdep_build_pkt(struct sdep_msg *msg, uint16_t command,
                                  const uint8_t *payload, uint8_t len,
                                  bool moredata) {
  msg->type = SdepCommand;
  msg->cmd_low = command & 0xff;
  msg->cmd_high = command >> 8;
  msg->len = len;
  msg->more = (moredata && len == SdepMaxPayload) ? 1 : 0;

  static_assert(sizeof(*msg) == 20, "msg is correctly packed");

  memcpy(msg->payload, payload, len);
}

// Read a single SDEP packet
static bool sdep_recv_pkt(struct sdep_msg *msg, uint16_t timeout) {
  bool success = false;
  uint16_t timerStart = timer_read();
  bool ready = false;

  do {
    ready = digitalRead(AdafruitBleIRQPin);
    if (ready) {
      break;
    }
    _delay_us(1);
  } while (timer_elapsed(timerStart) < timeout);

  if (ready) {
    SPI_begin(&spi);

    digitalWrite(AdafruitBleCSPin, PinLevelLow);

    do {
      // Read the command type, waiting for the data to be ready
      msg->type = spi_read_byte();
      if (msg->type == SdepSlaveNotReady || msg->type == SdepSlaveOverflow) {
        // Release it and let it initialize
        digitalWrite(AdafruitBleCSPin, PinLevelHigh);
        _delay_us(SdepBackOff);
        digitalWrite(AdafruitBleCSPin, PinLevelLow);
        continue;
      }

      // Read the rest of the header
      spi_recv_bytes(&msg->cmd_low, sizeof(*msg) - (1 + sizeof(msg->payload)));

      // and get the payload if there is any
      if (msg->len <= SdepMaxPayload) {
        spi_recv_bytes(msg->payload, msg->len);
      }
      success = true;
      break;
    } while (timer_elapsed(timerStart) < timeout);

    digitalWrite(AdafruitBleCSPin, PinLevelHigh);
  }
  return success;
}

static void resp_buf_read_one(bool greedy) {
  uint16_t last_send;
  if (!resp_buf.peek(last_send)) {
    return;
  }

  if (digitalRead(AdafruitBleIRQPin)) {
    struct sdep_msg msg;

again:
    if (sdep_recv_pkt(&msg, SdepTimeout)) {
      if (!msg.more) {
        // We got it; consume this entry
        resp_buf.get(last_send);
        dprintf("recv latency %dms\n", TIMER_DIFF_16(timer_read(), last_send));
      }

      if (greedy && resp_buf.peek(last_send) && digitalRead(AdafruitBleIRQPin)) {
        goto again;
      }
    }

  } else if (timer_elapsed(last_send) > SdepTimeout * 2) {
    dprintf("waiting_for_result: timeout, resp_buf size %d\n",
            (int)resp_buf.size());

    // Timed out: consume this entry
    resp_buf.get(last_send);
  }
}

static void send_buf_send_one(uint16_t timeout = SdepTimeout) {
  struct queue_item item;

  // Don't send anything more until we get an ACK
  if (!resp_buf.empty()) {
    return;
  }

  if (!send_buf.peek(item)) {
    return;
  }
  if (process_queue_item(&item, timeout)) {
    // commit that peek
    send_buf.get(item);
    dprintf("send_buf_send_one: have %d remaining\n", (int)send_buf.size());
  } else {
    dprint("failed to send, will retry\n");
    _delay_ms(SdepTimeout);
    resp_buf_read_one(true);
  }
}

static void resp_buf_wait(const char *cmd) {
  bool didPrint = false;
  while (!resp_buf.empty()) {
    if (!didPrint) {
      dprintf("wait on buf for %s\n", cmd);
      didPrint = true;
    }
    resp_buf_read_one(true);
  }
}

static bool ble_init(void) {
  state.initialized = false;
  state.configured = false;
  state.is_connected = false;

  pinMode(AdafruitBleIRQPin, PinDirectionInput);
  pinMode(AdafruitBleCSPin, PinDirectionOutput);
  digitalWrite(AdafruitBleCSPin, PinLevelHigh);

  SPI_init(&spi);

  // Perform a hardware reset
  pinMode(AdafruitBleResetPin, PinDirectionOutput);
  digitalWrite(AdafruitBleResetPin, PinLevelHigh);
  digitalWrite(AdafruitBleResetPin, PinLevelLow);
  _delay_ms(10);
  digitalWrite(AdafruitBleResetPin, PinLevelHigh);

  _delay_ms(1000); // Give it a second to initialize

  state.initialized = true;
  return state.initialized;
}

static inline uint8_t min(uint8_t a, uint8_t b) {
  return a < b ? a : b;
}

static bool read_response(char *resp, uint16_t resplen, bool verbose) {
  char *dest = resp;
  char *end = dest + resplen;

  while (true) {
    struct sdep_msg msg;

    if (!sdep_recv_pkt(&msg, 2 * SdepTimeout)) {
      dprint("sdep_recv_pkt failed\n");
      return false;
    }

    if (msg.type != SdepResponse) {
      *resp = 0;
      return false;
    }

    uint8_t len = min(msg.len, end - dest);
    if (len > 0) {
      memcpy(dest, msg.payload, len);
      dest += len;
    }

    if (!msg.more) {
      // No more data is expected!
      break;
    }
  }

  // Ensure the response is NUL terminated
  *dest = 0;

  // "Parse" the result text; we want to snip off the trailing OK or ERROR line
  // Rewind past the possible trailing CRLF so that we can strip it
  --dest;
  while (dest > resp && (dest[0] == '\n' || dest[0] == '\r')) {
    *dest = 0;
    --dest;
  }

  // Look back for start of preceeding line
  char *last_line = strrchr(resp, '\n');
  if (last_line) {
    ++last_line;
  } else {
    last_line = resp;
  }

  bool success = false;
  static const char kOK[] PROGMEM = "OK";

  success = !strcmp_P(last_line, kOK );

  if (verbose || !success) {
    dprintf("result: %s\n", resp);
  }
  return success;
}

static bool at_command(const char *cmd, char *resp, uint16_t resplen,
                       bool verbose, uint16_t timeout) {
  const char *end = cmd + strlen(cmd);
  struct sdep_msg msg;

  if (verbose) {
    dprintf("ble send: %s\n", cmd);
  }

  if (resp) {
    // They want to decode the response, so we need to flush and wait
    // for all pending I/O to finish before we start this one, so
    // that we don't confuse the results
    resp_buf_wait(cmd);
    *resp = 0;
  }

  // Fragment the command into a series of SDEP packets
  while (end - cmd > SdepMaxPayload) {
    sdep_build_pkt(&msg, BleAtWrapper, (uint8_t *)cmd, SdepMaxPayload, true);
    if (!sdep_send_pkt(&msg, timeout)) {
      return false;
    }
    cmd += SdepMaxPayload;
  }

  sdep_build_pkt(&msg, BleAtWrapper, (uint8_t *)cmd, end - cmd, false);
  if (!sdep_send_pkt(&msg, timeout)) {
    return false;
  }

  if (resp == NULL) {
    auto now = timer_read();
    while (!resp_buf.enqueue(now)) {
      resp_buf_read_one(false);
    }
    auto later = timer_read();
    if (TIMER_DIFF_16(later, now) > 0) {
      dprintf("waited %dms for resp_buf\n", TIMER_DIFF_16(later, now));
    }
    return true;
  }

  return read_response(resp, resplen, verbose);
}

bool at_command_P(const char *cmd, char *resp, uint16_t resplen, bool verbose) {
  auto cmdbuf = (char *)alloca(strlen_P(cmd) + 1);
  strcpy_P(cmdbuf, cmd);
  return at_command(cmdbuf, resp, resplen, verbose);
}

bool adafruit_ble_is_connected(void) {
  return state.is_connected;
}

bool adafruit_ble_enable_keyboard(void) {
  char resbuf[128];

  if (!state.initialized && !ble_init()) {
    return false;
  }

  state.configured = false;

  // Disable command echo
  static const char kEcho[] PROGMEM = "ATE=0";
  // Make the advertised name match the keyboard
  static const char kGapDevName[] PROGMEM =
      "AT+GAPDEVNAME=" STR(PRODUCT) " " STR(DESCRIPTION);
  // Turn on keyboard support
  static const char kHidEnOn[] PROGMEM = "AT+BLEHIDEN=1";

  // Adjust intervals to improve latency.  This causes the "central"
  // system (computer/tablet) to poll us every 10-30 ms.  We can't
  // set a smaller value than 10ms, and 30ms seems to be the natural
  // processing time on my macbook.  Keeping it constrained to that
  // feels reasonable to type to.
  static const char kGapIntervals[] PROGMEM = "AT+GAPINTERVALS=10,30,,";

  // Reset the device so that it picks up the above changes
  static const char kATZ[] PROGMEM = "ATZ";

  // Turn down the power level a bit
  static const char kPower[] PROGMEM = "AT+BLEPOWERLEVEL=-12";
  static PGM_P const configure_commands[] PROGMEM = {
    kEcho,
    kGapIntervals,
    kGapDevName,
    kHidEnOn,
    kPower,
    kATZ,
  };

  uint8_t i;
  for (i = 0; i < sizeof(configure_commands) / sizeof(configure_commands[0]);
       ++i) {
    PGM_P cmd;
    memcpy_P(&cmd, configure_commands + i, sizeof(cmd));

    if (!at_command_P(cmd, resbuf, sizeof(resbuf))) {
      dprintf("failed BLE command: %S: %s\n", cmd, resbuf);
      goto fail;
    }
  }

  state.configured = true;

  // Check connection status in a little while; allow the ATZ time
  // to kick in.
  state.last_connection_update = timer_read();
fail:
  return state.configured;
}

static void set_connected(bool connected) {
  if (connected != state.is_connected) {
    if (connected) {
      print("****** BLE CONNECT!!!!\n");
    } else {
      print("****** BLE DISCONNECT!!!!\n");
    }
    state.is_connected = connected;

    // TODO: if modifiers are down on the USB interface and
    // we cut over to BLE or vice versa, they will remain stuck.
    // This feels like a good point to do something like clearing
    // the keyboard and/or generating a fake all keys up message.
    // However, I've noticed that it takes a couple of seconds
    // for macOS to to start recognizing key presses after BLE
    // is in the connected state, so I worry that doing that
    // here may not be good enough.
  }
}

void adafruit_ble_task(void) {
  char resbuf[48];

  if (!state.configured && !adafruit_ble_enable_keyboard()) {
    return;
  }
  resp_buf_read_one(true);
  send_buf_send_one(SdepShortTimeout);

  if (resp_buf.empty() && (state.event_flags & UsingEvents) &&
      digitalRead(AdafruitBleIRQPin)) {
    // Must be an event update
    if (at_command_P(PSTR("AT+EVENTSTATUS"), resbuf, sizeof(resbuf))) {
      uint32_t mask = strtoul(resbuf, NULL, 16);

      if (mask & BleSystemConnected) {
        set_connected(true);
      } else if (mask & BleSystemDisconnected) {
        set_connected(false);
      }
    }
  }

  if (timer_elapsed(state.last_connection_update) > ConnectionUpdateInterval) {
    bool shouldPoll = true;
    if (!(state.event_flags & ProbedEvents)) {
      // Request notifications about connection status changes.
      // This only works in SPIFRIEND firmware > 0.6.7, which is why
      // we check for this conditionally here.
      // Note that at the time of writing, HID reports only work correctly
      // with Apple products on firmware version 0.6.7!
      // https://forums.adafruit.com/viewtopic.php?f=8&t=104052
      if (at_command_P(PSTR("AT+EVENTENABLE=0x1"), resbuf, sizeof(resbuf))) {
        at_command_P(PSTR("AT+EVENTENABLE=0x2"), resbuf, sizeof(resbuf));
        state.event_flags |= UsingEvents;
      }
      state.event_flags |= ProbedEvents;

      // leave shouldPoll == true so that we check at least once
      // before relying solely on events
    } else {
      shouldPoll = false;
    }

    static const char kGetConn[] PROGMEM = "AT+GAPGETCONN";
    state.last_connection_update = timer_read();

    if (at_command_P(kGetConn, resbuf, sizeof(resbuf))) {
      set_connected(atoi(resbuf));
    }
  }

#ifdef SAMPLE_BATTERY
  // I don't know if this really does anything useful yet; the reported
  // voltage level always seems to be around 3200mV.  We may want to just rip
  // this code out.
  if (timer_elapsed(state.last_battery_update) > BatteryUpdateInterval &&
      resp_buf.empty()) {
    state.last_battery_update = timer_read();

    if (at_command_P(PSTR("AT+HWVBAT"), resbuf, sizeof(resbuf))) {
      state.vbat = atoi(resbuf);
    }
  }
#endif
}

static bool process_queue_item(struct queue_item *item, uint16_t timeout) {
  char cmdbuf[48];
  char fmtbuf[64];

  // Arrange to re-check connection after keys have settled
  state.last_connection_update = timer_read();

#if 1
  if (TIMER_DIFF_16(state.last_connection_update, item->added) > 0) {
    dprintf("send latency %dms\n",
            TIMER_DIFF_16(state.last_connection_update, item->added));
  }
#endif

  switch (item->queue_type) {
    case QTKeyReport:
      strcpy_P(fmtbuf,
          PSTR("AT+BLEKEYBOARDCODE=%02x-00-%02x-%02x-%02x-%02x-%02x-%02x"));
      snprintf(cmdbuf, sizeof(cmdbuf), fmtbuf, item->key.modifier,
               item->key.keys[0], item->key.keys[1], item->key.keys[2],
               item->key.keys[3], item->key.keys[4], item->key.keys[5]);
      return at_command(cmdbuf, NULL, 0, true, timeout);

    case QTConsumer:
      strcpy_P(fmtbuf, PSTR("AT+BLEHIDCONTROLKEY=0x%04x"));
      snprintf(cmdbuf, sizeof(cmdbuf), fmtbuf, item->consumer);
      return at_command(cmdbuf, NULL, 0, true, timeout);

#ifdef MOUSE_ENABLE
    case QTMouseMove:
      strcpy_P(fmtbuf, PSTR("AT+BLEHIDMOUSEMOVE=%d,%d,%d,%d"));
      snprintf(cmdbuf, sizeof(cmdbuf), fmtbuf, item->mousemove.x,
          item->mousemove.y, item->mousemove.scroll, item->mousemove.pan);
      if (!at_command(cmdbuf, NULL, 0, true, timeout)) {
        return false;
      }
      strcpy_P(cmdbuf, PSTR("AT+BLEHIDMOUSEBUTTON="));
      if (item->mousemove.buttons & MOUSE_BTN1) {
        strcat(cmdbuf, "L");
      }
      if (item->mousemove.buttons & MOUSE_BTN2) {
        strcat(cmdbuf, "R");
      }
      if (item->mousemove.buttons & MOUSE_BTN3) {
        strcat(cmdbuf, "M");
      }
      if (item->mousemove.buttons == 0) {
        strcat(cmdbuf, "0");
      }
      return at_command(cmdbuf, NULL, 0, true, timeout);
#endif
    default:
      return true;
  }
}

bool adafruit_ble_send_keys(uint8_t hid_modifier_mask, uint8_t *keys,
                            uint8_t nkeys) {
  struct queue_item item;
  bool didWait = false;

  item.queue_type = QTKeyReport;
  item.key.modifier = hid_modifier_mask;
  item.added = timer_read();

  while (nkeys >= 0) {
    item.key.keys[0] = keys[0];
    item.key.keys[1] = nkeys >= 1 ? keys[1] : 0;
    item.key.keys[2] = nkeys >= 2 ? keys[2] : 0;
    item.key.keys[3] = nkeys >= 3 ? keys[3] : 0;
    item.key.keys[4] = nkeys >= 4 ? keys[4] : 0;
    item.key.keys[5] = nkeys >= 5 ? keys[5] : 0;

    if (!send_buf.enqueue(item)) {
      if (!didWait) {
        dprint("wait for buf space\n");
        didWait = true;
      }
      send_buf_send_one();
      continue;
    }

    if (nkeys <= 6) {
      return true;
    }

    nkeys -= 6;
    keys += 6;
  }

  return true;
}

bool adafruit_ble_send_consumer_key(uint16_t keycode, int hold_duration) {
  struct queue_item item;

  item.queue_type = QTConsumer;
  item.consumer = keycode;

  while (!send_buf.enqueue(item)) {
    send_buf_send_one();
  }
  return true;
}

#ifdef MOUSE_ENABLE
bool adafruit_ble_send_mouse_move(int8_t x, int8_t y, int8_t scroll,
                                  int8_t pan, uint8_t buttons) {
  struct queue_item item;

  item.queue_type = QTMouseMove;
  item.mousemove.x = x;
  item.mousemove.y = y;
  item.mousemove.scroll = scroll;
  item.mousemove.pan = pan;
  item.mousemove.buttons = buttons;

  while (!send_buf.enqueue(item)) {
    send_buf_send_one();
  }
  return true;
}
#endif

uint32_t adafruit_ble_read_battery_voltage(void) {
  return state.vbat;
}

bool adafruit_ble_set_mode_leds(bool on) {
  if (!state.configured) {
    return false;
  }

  // The "mode" led is the red blinky one
  at_command_P(on ? PSTR("AT+HWMODELED=1") : PSTR("AT+HWMODELED=0"), NULL, 0);

  // Pin 19 is the blue "connected" LED; turn that off too.
  // When turning LEDs back on, don't turn that LED on if we're
  // not connected, as that would be confusing.
  at_command_P(on && state.is_connected ? PSTR("AT+HWGPIO=19,1")
                                        : PSTR("AT+HWGPIO=19,0"),
               NULL, 0);
  return true;
}

// https://learn.adafruit.com/adafruit-feather-32u4-bluefruit-le/ble-generic#at-plus-blepowerlevel
bool adafruit_ble_set_power_level(int8_t level) {
  char cmd[46];
  if (!state.configured) {
    return false;
  }
  snprintf(cmd, sizeof(cmd), "AT+BLEPOWERLEVEL=%d", level);
  return at_command(cmd, NULL, 0, false);
}