Add support for Adafruit BLE modules

This implements some helper functions that allow sending key reports
to an SPI based Bluetooth Low Energy module, such as the Adafruit
Feather 32u4 Bluefruit LE.

There is some plumbing required in lufa.c to enable this; that
is in a follow-on commit.

3 files changed, 931 insertions, 0 deletions

diff --git a/tmk_core/protocol/lufa/adafruit_ble.cpp b/tmk_core/protocol/lufa/adafruit_ble.cpp
new file mode 100644
index 0000000000..37194e77a9
--- /dev/null
+++ b/tmk_core/protocol/lufa/adafruit_ble.cpp
@@ -0,0 +1,805 @@
+#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)) {
+      uint8_t x, y, scroll, pan;
+    } 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);
+      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) {
+  struct queue_item item;
+
+  item.queue_type = QTMouseMove;
+  item.mousemove.x = x;
+  item.mousemove.y = y;
+  item.mousemove.scroll = scroll;
+  item.mousemove.pan = pan;
+
+  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);
+}
diff --git a/tmk_core/protocol/lufa/adafruit_ble.h b/tmk_core/protocol/lufa/adafruit_ble.h
new file mode 100644
index 0000000000..351fd55ae9
--- /dev/null
+++ b/tmk_core/protocol/lufa/adafruit_ble.h
@@ -0,0 +1,60 @@
+/* Bluetooth Low Energy Protocol for QMK.
+ * Author: Wez Furlong, 2016
+ * Supports the Adafruit BLE board built around the nRF51822 chip.
+ */
+#pragma once
+#ifdef ADAFRUIT_BLE_ENABLE
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Instruct the module to enable HID keyboard support and reset */
+extern bool adafruit_ble_enable_keyboard(void);
+
+/* Query to see if the BLE module is connected */
+extern bool adafruit_ble_query_is_connected(void);
+
+/* Returns true if we believe that the BLE module is connected.
+ * This uses our cached understanding that is maintained by
+ * calling ble_task() periodically. */
+extern bool adafruit_ble_is_connected(void);
+
+/* Call this periodically to process BLE-originated things */
+extern void adafruit_ble_task(void);
+
+/* Generates keypress events for a set of keys.
+ * The hid modifier mask specifies the state of the modifier keys for
+ * this set of keys.
+ * Also sends a key release indicator, so that the keys do not remain
+ * held down. */
+extern bool adafruit_ble_send_keys(uint8_t hid_modifier_mask, uint8_t *keys,
+                                   uint8_t nkeys);
+
+/* Send a consumer keycode, holding it down for the specified duration
+ * (milliseconds) */
+extern bool adafruit_ble_send_consumer_key(uint16_t keycode, int hold_duration);
+
+#ifdef MOUSE_ENABLE
+/* Send a mouse/wheel movement report.
+ * The parameters are signed and indicate positive of negative direction
+ * change. */
+extern bool adafruit_ble_send_mouse_move(int8_t x, int8_t y, int8_t scroll,
+                                         int8_t pan);
+#endif
+
+/* Compute battery voltage by reading an analog pin.
+ * Returns the integer number of millivolts */
+extern uint32_t adafruit_ble_read_battery_voltage(void);
+
+extern bool adafruit_ble_set_mode_leds(bool on);
+extern bool adafruit_ble_set_power_level(int8_t level);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // ADAFRUIT_BLE_ENABLE
diff --git a/tmk_core/protocol/lufa/ringbuffer.hpp b/tmk_core/protocol/lufa/ringbuffer.hpp
new file mode 100644
index 0000000000..70a3c4881d
--- /dev/null
+++ b/tmk_core/protocol/lufa/ringbuffer.hpp
@@ -0,0 +1,66 @@
+#pragma once
+// A simple ringbuffer holding Size elements of type T
+template <typename T, uint8_t Size>
+class RingBuffer {
+ protected:
+  T buf_[Size];
+  uint8_t head_{0}, tail_{0};
+ public:
+  inline uint8_t nextPosition(uint8_t position) {
+    return (position + 1) % Size;
+  }
+
+  inline uint8_t prevPosition(uint8_t position) {
+    if (position == 0) {
+      return Size - 1;
+    }
+    return position - 1;
+  }
+
+  inline bool enqueue(const T &item) {
+    static_assert(Size > 1, "RingBuffer size must be > 1");
+    uint8_t next = nextPosition(head_);
+    if (next == tail_) {
+      // Full
+      return false;
+    }
+
+    buf_[head_] = item;
+    head_ = next;
+    return true;
+  }
+
+  inline bool get(T &dest, bool commit = true) {
+    auto tail = tail_;
+    if (tail == head_) {
+      // No more data
+      return false;
+    }
+
+    dest = buf_[tail];
+    tail = nextPosition(tail);
+
+    if (commit) {
+      tail_ = tail;
+    }
+    return true;
+  }
+
+  inline bool empty() const { return head_ == tail_; }
+
+  inline uint8_t size() const {
+    int diff = head_ - tail_;
+    if (diff >= 0) {
+      return diff;
+    }
+    return Size + diff;
+  }
+
+  inline T& front() {
+    return buf_[tail_];
+  }
+
+  inline bool peek(T &item) {
+    return get(item, false);
+  }
+};