Question

我喜欢为我现有的家庭自动化系统创建一种室内跟踪系统。我想过使用BLE。我已经在Raspberry Pi上成功设置了hcitool，我可以毫无问题地连接到我的iPhone。但是如何在不连接它的情况下获得Raspberry Pi和iPhone之间的信号强度。我已经尝试使用sudo hcitool cc [BTADDRESS]连接到我的iPhone而无需身份验证，但看起来iPhone不允许这些连接保持打开状态。我认为这必须是一种在不连接两个设备的情况下获得信号强度的方法。我想用它来确定从我的Raspberry Pi到我的iPhone的距离。我可以计算一下我需要发现iPhone的距离吗？

Answer 1

有两种方法可以实现，到目前为止，我只能在Android设备上可靠地工作。

利用智能手机的蓝牙友好名称并设置discoverability to infinite。我写了一个简单的应用程序。由于保留了可发现性设置，因此在应用程序被杀死之后也可以在后台运行。据我所知，这在iOS中是不可能的。
在手机的BLE数据包中宣传UUID。这可以通过Android和iOS设备完成。但是，在后台，iPhone会将广告切换到缩小模式，使数据包无法识别。在后台识别广告iOS设备的问题仍然是open。

在树莓上，我使用PyBluez扫描并寻找运行（1）或（2）的智能手机的存在。我举报代码示例：

import bluetooth
import bluetooth._bluetooth as bluez
import struct, socket, sys, select
def hci_enable_le_scan(sock):
    hci_toggle_le_scan(sock, 0x01)

#Discover name and RSS of enabled BLE devices
class MyDiscoverer(bluetooth.DeviceDiscoverer):

    def pre_inquiry(self):
        self.done = False

    def device_discovered(self, address, device_class, rssi, name):
        discovery_logger.info("Discovered %s" % (address, ))
        if name == "YOUR-DEVICE-FRIENDLY_NAME":
            #Use the RSS for your detection / localization system

    def inquiry_complete(self):
        self.done = True

#Performs inquiry for name request
def async_inquiry():
    d = MyDiscoverer()
    while True:
        d.find_devices(lookup_names = True)
        readfiles = [ d, ]
        while True:
            rfds = select.select( readfiles, [], [] )[0]
            if d in rfds:
                d.process_event()
            if d.done:
                break
        time.sleep(DISCOVERY_INTERVAL)

#Parse received advertising packets
def parse_events(sock):
# save current filter
old_filter = sock.getsockopt( bluez.SOL_HCI, bluez.HCI_FILTER, 14)

flt = bluez.hci_filter_new()
bluez.hci_filter_all_events(flt)
bluez.hci_filter_set_ptype(flt, bluez.HCI_EVENT_PKT)
sock.setsockopt( bluez.SOL_HCI, bluez.HCI_FILTER, flt )
while True:
    pkt = sock.recv(255)
    ptype, event, plen = struct.unpack("BBB", pkt[:3])
    if event == LE_META_EVENT:
        subevent, = struct.unpack("B", pkt[3])
        pkt = pkt[4:]
        if subevent == EVT_LE_CONN_COMPLETE:
            le_handle_connection_complete(pkt)
        elif subevent == EVT_LE_ADVERTISING_REPORT:
            #Check if the advertisement is the one we are searching for
            if getASCII(pkt[start:end]) == "YOUR-UUID"
                report_pkt_offset = 0
                report_data_length, = struct.unpack("B", pkt[report_pkt_offset + 9])
                # each report is 2 (event type, bdaddr type) + 6 (the address)
                #    + 1 (data length field) + report_data length + 1 (rssi)
                report_pkt_offset = report_pkt_offset +  10 + report_data_length + 1
                rssi, = struct.unpack("b", pkt[report_pkt_offset -1])
                #Now you have the RSS indicator, use it for monitoring / localization

sock.setsockopt( bluez.SOL_HCI, bluez.HCI_FILTER, old_filter )
dev_id = 0
try:
    sock = bluez.hci_open_dev(dev_id)
except:
    print "error accessing bluetooth device..."
    sys.exit(1)

p = threading.Thread(group=None, target=parse_events, name='parsing', args=(sock, ))
d = threading.Thread(group=None, target=async_inquiry, name='async_inquiry', args=())
try:
    p.start()
except:
    print "Error: unable to start parsing thread"

try:
    d.start()
except:
    print "Error: unable to start asynchronous discovery thread"

在没有配对的情况下，在BT设备的Raspberry Pi上获得蓝牙信号强度

1 个答案: