0

I am using the HM-10 as iBeacon and the Tx Power is set to -59 by default. I want to change the Tx Power and the datasheet said that AT+MEAS can be used to set iBeacon measured power. After calibration the RSSI at 1 meter was -23dBm which is E9 in hexadecimals. So I tried using command AT+MEASE9 and AT+MEAS0xE9 but I did not get any response form the BLE. So how can I change the Tx Power of my BLE? Thanks

Here is the datasheet: http://fab.cba.mit.edu/classes/863.15/doc/tutorials/programming/bluetooth/bluetooth40_en.pdf

Mark
  • 9
  • 1
  • 5

1 Answers1

0

The data sheet is clear, AT+MEAS can be used to set iBeacon measured power, but you don't use the correct parameters. The parameter range = 0x0001 to 0xFFFE. To set it you have to send AT+MEASFFE9. This is the default setting(-23dbm). This value is not the transmitted power, but a factory-calibrated, read-only constant which indicates what's the expected RSSI at a distance of 1 meter to the beacon. Combined with RSSI, it allows you to estimate the distance between the device and the beacon. To really change the transmitting power you have to use AT+POWE[parameter]. The possible settings are 0: -23dbm,1: -6dbm, 2: 0dbm, 3: 6dbm. So To set it to 6dbm send AT+POWE3. This will affect battery life and the iBeacon measured power has to be calibrated with a new value.

GrooverFromHolland
  • 971
  • 1
  • 11
  • 18
  • I tried to change the factory-calibration as you mentioned by writing AT+MEASFFE9 to the Arduino Serial Monitor but still did not get any response. What might be the problem? Thanks for your quick response. – Mark Nov 10 '17 at 09:40
  • Even AT+MEAS? does not get any response. – Mark Nov 10 '17 at 10:19
  • If you don't get any response there is a lot that can be wrong. It is too much to discuss every thing here so recommend this tutorial: http://www.martyncurrey.com/hm-10-bluetooth-4ble-modules/ – GrooverFromHolland Nov 10 '17 at 17:31
  • I have read it already. But one more question. If I set the HM-10 up as a beacon and open a BLE Location app then the RSSI is always -45dBm or -46dBm even if I am 5 meters away. Why is that so? – Mark Nov 10 '17 at 18:00
  • It can be the app you are using, but also the position and surrounding objects of the bluetooth antenna. I have multiple hm10 devices. One is build in a half open metal enclosure and has a sort of directional effect, at 1 meter it is at -75 dbm and at 5 meter -80. An other is in open air, free of objects and wires reading -25 at 1 meter , -50 at 5 meters and -75 at 12 meters, using the Nordic nRF Toolbox. – GrooverFromHolland Nov 10 '17 at 18:47
  • So I tried everything right now. When the HM-10 was not in the beacon mode I got an RSSI of -10dBm at 10cm apart and at 5 meters the RSSI was -47dBm. If I the distance between the BLE and phone was 10 meters then it was still -47dBm...weird. I also tried the beacon mode and in the beacon mode I got an RSSI of -47dBm at 10cm apart and the dBm never dropped below that. It is like there is a block on the HM-10 that does not let it give a dBm below -47. Before I updated the firmware I remember it gave out a dBm of -80 atleast but v540 should be an okei firmware as far as I have heard. – Mark Nov 10 '17 at 19:56
  • It can not be the hm10 itself it is just a transmitter. if it is at the default setting(0dbm) The rssi at 1 meter is about -23 at 5 meter it will be about - 50 and the maximum range is 70 meters in ideal conditions(-100). What app are you using? – GrooverFromHolland Nov 10 '17 at 20:21
  • So I tried Beacon Simulator, BLE Scanner, Beacon Scanner, Locate, Dartle.io and I just downloaded nRF Connect. I tried out the nRFConnect (without beacon mode) without connecting and the result was same...the RSSI was -10 nearby and stayed at -47 from 5 meters and onwards. But then I tried connecting the HM-10 to the nRF Connect app and I pushed the "Read remote RSSI" and that actually worked. At 10cm=-15dBm, 1meter=-59dBm, 10meter=-80dBm. So it only worked when connected but beacons should not connect to the app - they should only advertise. So why did a connection make all the difference? – Mark Nov 10 '17 at 22:06
  • No more ideas from me, I read my values not connected. I use my own written apps(uwp and adroid) and nrf Tools on my laptop and phone to maesure RSSI, and have no problems. – GrooverFromHolland Nov 10 '17 at 23:33
  • But what firmware does you HM-10 have? And do you get a response using AT+MEAS command? – Mark Nov 11 '17 at 11:18
  • Did you manage to solve AT+MEAS problem @Mark ? I run into the same problem – Janice Kartika Dec 26 '17 at 11:13
  • Nope. But I got the Beacon working with an Iphone. The Beacon did not work with Android – Mark Mar 07 '18 at 20:39