rcvd/rcvd.js

// RCVD.js: a small library for syncing time on BLE-enabled Casio watches
// Tested on: GW-B5600BC, GMW-B5000D, OCW-T200S, GM-B2100BD
// Compatible with both KaiOS 2.5.x and in-progress Web Bluetooth API spec
// Created by Luxferre in 2022, released into public domain

RCVD = (function(nav) {
  var readerChar, writerChar, outputQueue, wt,
    isKai = 'mozBluetooth' in nav && !('bluetooth' in nav), //whether or not we're interacting using non-standard KaiOS 2.5.x API
    btx = isKai ? nav.mozBluetooth : nav.bluetooth,
    waitForOutput = _ => new Promise((res, rej) => {
      (wt = function() {
        if(outputQueue.length)
          res(outputQueue.pop())
        else setTimeout(wt, 1)
      })()
    }),
    watchModel = '',
    localgatt = null, //local GATT reference for disconnection
    TD = new TextDecoder(),
    ids = s => `26eb00${s}-b012-49a8-b1f8-394fb2032b0f`,
    scanids = ['00001804-0000-1000-8000-00805f9b34fb', ids('0d')],
    connectWatch = disconnectCb => new Promise((res, rej) => {
      if(!disconnectCb) disconnectCb = ()=>{}
      if(isKai) {
        var adp = btx.defaultAdapter
        adp.startLeScan(scanids).then(dHandle => {
          dHandle.ondevicefound = e => {
            adp.stopLeScan(dHandle)
            localgatt = e.device.gatt
            localgatt.connect(false).then(_ => {
              outputQueue = []
              localgatt.oncharacteristicchanged = e => {
                outputQueue.push(new Uint8Array(e.characteristic.value))
              }
              localgatt.discoverServices().then(_ => {
                for(let srv of localgatt.services) {
                  for(var chr of srv.characteristics) {
                    if(chr.uuid === ids('2c')) {
                      readerChar = chr
                      readerChar.writeValueWithoutResponse = readerChar.writeValue
                    }
                    else if(chr.uuid === ids('2d')) {
                      writerChar = chr
                      writerChar.writeValueWithResponse = writerChar.writeValue
                    }
                  }
                }
                writerChar.startNotifications().then(res).catch(rej)
              })
            }).catch(rej)
          }
        }).catch(rej)
      }
      else btx.requestDevice({filters:[{services:[scanids[0]]},{services:[scanids[1]]}]})
        .then(dev => {
          dev.addEventListener('gattserverdisconnected', disconnectCb)
          localgatt = dev.gatt
          return localgatt.connect()
        })
        .then(conn => conn.getPrimaryService(ids('0d')))
        .then(srv => srv.getCharacteristics())
        .then(arr => {
          for(let chr of arr) {
            if(chr.uuid === ids('2c'))
              readerChar = chr
            else if(chr.uuid === ids('2d'))
              writerChar = chr
          }
          outputQueue = []
          writerChar.startNotifications().then(chr => {
            chr.addEventListener('characteristicvaluechanged', e => {
              outputQueue.push(new Uint8Array(e.target.value.buffer))
            })
            res()
          }).catch(rej)
        }).catch(rej)
    }),
    execReadCmd = (...args) => readerChar.writeValueWithoutResponse(Uint8Array.from(args).buffer).then(waitForOutput),
    execWriteCmd = cmddata => writerChar.writeValueWithResponse(cmddata.buffer),

    //some logic needed to init the time sync process
    //these parameters need to be read from the watch and then written back

    plgen = k => [...Array(6)].map((a,i)=>[k,i]), //property list generator
    cyclePresyncProperties = _ => new Promise((res, rej) => {
      var slist = [...plgen(30),...plgen(31)]
      if(watchModel.indexOf('OCW') > 5)
        slist = [[30,0],[30,1]]
      else if(watchModel.indexOf('B2100') > 5)
        slist = [[30,0],[30,1],[31,0],[31,1]]
      var plist = [[29,0], [29,2], [29,4]].concat(slist); //populate the props list
      (function cycle() {
        var p = plist.shift()
        if(p) //we still have properties
          execReadCmd.apply(null, p)
            .then(execWriteCmd)
            .then(cycle).catch(rej)
        else //properties over
          res()
      })()
    })

  return {
    connect: dcb => new Promise((res, rej) => { //resolve to true if full setting mode, or false if just sync
      connectWatch(dcb)
        .then(_ => execReadCmd(0x23).then(v => watchModel = TD.decode(v).slice(1).replace(/\x00/g,''))) 
        .then(_ => execReadCmd(0x10))
        .then(features => {
          if(features[8]<2) { //we entered full setting mode, sync application info first
            execReadCmd(0x22).then(info => //set the correct initialization after BLE reset on the watch
              (info[11] || Math.min(...info.slice(1,11))^255) ? info :
                execWriteCmd(Uint8Array.from([0x22, 0x34, 0x88, 0xF4, 0xE5, 0xD5, 0xAF, 0xC8, 0x29, 0xE0, 0x6D, 0x02]))
            ).then(info => {
              if(info instanceof Promise)
                info.then(_=>res(true)).catch(rej)
              else res(true)
            }).catch(rej)
          }
          else res(false)
        }).catch(rej)
    }),
    getModel: _ => watchModel,
    rawRead: execReadCmd,
    rawWrite: execWriteCmd,
    sync: dObj => new Promise((res, rej) => {
      cyclePresyncProperties().then(_ => {
        //set to the next second to make up for latency
        var d = dObj || new Date(Date.now() + 1000), year = d.getFullYear()
        execWriteCmd(Uint8Array.from([
          9,
          year&255, year>>>8,
          d.getMonth()+1, d.getDate(),
          d.getHours(), d.getMinutes(), d.getSeconds(), 
          d.getDay(), 0, 0, 1
        ])).then(res).catch(res) //not a mistake!
      }).catch(rej)
    }),
    disconnect: _ => {
      if(localgatt) {
        localgatt.disconnect()
        localgatt = null
      }
    }
  }
})(navigator)