How can I set the sampling rate in a Movesense device? - ios
I can subscribe to the acceleration or angular velocity values with the movesense mobile libraries, but is there a way to change the sampling rate of the sensor?
The new movesense-device-lib (released today) has the new sensor API's that make it possible. The API's provide convenient and generic way to access all the "fast" sensors: Accelerometer, Gyroscope and Magnetic field. The paths have also been changed to make them less verbose (saves flash memory).
Here's a small intro on how the new API's work:
For each sensor there is a resource under root /Meas. /Meas/Acc, /Meas/Gyro and /Meas/Magn and they all work the same way.
Under the sensors root there is an Info resource that returns available sample rates as well as ranges. This is the result from GET'ing the /Meas/Acc/Info:
{
"SampleRates" : [13,26,52,104,208],
"Ranges" : [2,4,8,16]
}
Also under the sensors root there is a Config resource when one can GET & PUT the sensors global settings. At the moment the only setting in Accelerometer is GRange.
The data can be only SUBSCRIBED (no more GET in API), and the sample rate wanted is set as URL parameter: /Meas/Acc/{SampleRate} where the {SampleRate} is one of the values from the Info resource.
The sbuscribed data is returned in the object of the form: {timestamp, array of FloatVector3D's}. Different sample rates can return different number of measurements per notification in the array.
Word of caution: We have tested the accelerometer upto 208 Hz (as of today) so even if the API advertises higher rates, we have not yet tested how far we can push the sensor in practice.
Full Disclosure: I work for Movesense team
Related
Writing BLE to Cycling Control Point - Adding Resistance
I have bee working with BLE for a while now, but primarily for reading and notifying characteristics.
The devices specifically are Virtual cycle trainers that support GATTS Cycling Power Service - 0x1818 link
I know that it's possible to increase resistance on this trainer, but I have read the documentation on Cycling Power Control Point - 0x2A66 [link][2] which is the only one with Mandatory write functions, but non of the documentation seem to be make sense.
Trainer: Cycleops Magnus
Reading and writing characteristic
// Reads all characteristics
var characteristics = service.characteristics;
for(BluetoothCharacteristic c in characteristics) {
List<int> value = await device.readCharacteristic(c);
print(value);
}
// Writes to a characteristic
await device.writeCharacteristic(c, [0x12, 0x34])
Reading and writing descriptors
// Reads all descriptors
var descriptors = characteristic.descriptors;
for(BluetoothDescriptor d in descriptors) {
List<int> value = await device.readDescriptor(d);
print(value);
}
// Writes to a descriptor
await device.writeDescriptor(d, [0x12, 0x34])
The closest I can see is setting the crank length, or chain weight but at this stage I am only guessing and am looking for some guidance.
The questions is this..
What characteristic or descriptor should I use to adjust Virtual Power
trainer resistance and what is the best way to do this?
Any coding Language is fine, I can transpose it.
Screenshot of services available for device
[2]: https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.cycling_power_control_point.xml
I think you're using the wrong Bluetooth service for this. The Cycling Power Service is for collecting data from cycling power meters like this one: https://www.cyclist.co.uk/reviews/6705/long-term-review-fsa-powerbox-carbon-power-cranks For your requirements, I believe you should be using the Fitness Machine Service (0x1826) which includes the Indoor Bike Data characteristic (0x2AD2) and most importantly for you, the Fitness Machine Control Point characteristic. Take a look at section 4.16.1 of the Fitness Machine Service specification and you'll see details of operations which the control point supports, including a reference to 4.16.2.5 Set Target Resistance Level Procedure. I think this is what you need.
You cannot use cycling control point(CPP) for adding resistance. CPP can only be used to copy data like wheel Revolution from old peripheral to new one or if you want to reset data on peripheral you can use cpp. If you want to add resistance you need to check for fitness machine i am using elite and elite have Fitness Machine Control point you can write resistance and other things like inclination, elevation etc using FTCP. Few of the vendor support fitness machine and other have given their api or source code you can use that to add resistance and other stuff like that.
Indoor trainers have a few services: Cycling Power Service (ANT+ or BT also have) ANT+FEC (ANT only) BTLE Fitness control (FTMS) TACX ANT+ FEC. over Bluetooth (https://blog.lazerwalker.com/2019/02/15/bike-game-part-2.html) Wahoo's Extension to the Cycling Power Service (to be able to set Target power for instance) To Add Resistance to the trainer to #1, you need to check if it also has the #5 service as well. (this is the UUID used - A026E005-0A7D-4AB3-97FA-F1500F9FEB8B) #4 is actually a protocol which Tacx came up w/ before FTMS was a standard and some trainers still use this.
Lowest value from 2 payloads in Node-Red
I have a IoT system in home and two temperature sensors.
One of the sensors could work in some hours in direct sun.
The real temperature is always the lowest value, so sometimes temp1, sometimes temp2.
What I want to achieve is:
read the temperature from sensors1 (via MQTT)
read the temperature from sensors2 (via MQTT)
compare values
find the lowest one and send in via MQTT
go back to reading in loop
For this example I can simulate readings with injection nodes
How to do that? I am new in Node-Red, have tried but without success.
Here is my flow:
[{"id":"fa6372cc.47f92","type":"tab","label":"Flow 8","disabled":false,"info":""},{"id":"5ac90e03.22da3","type":"join","z":"fa6372cc.47f92","name":"","mode":"custom","build":"object","property":"payload","propertyType":"msg","key":"topic","joiner":"","joinerType":"str","accumulate":true,"timeout":"","count":"2","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"","reduceFixup":"","x":990,"y":340,"wires":[["f09774bf.3c8428","a197b84d.6a7338"]]},{"id":"f09774bf.3c8428","type":"debug","z":"fa6372cc.47f92","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","x":1130,"y":340,"wires":[]},{"id":"43900e79.98cd8","type":"change","z":"fa6372cc.47f92","name":"set payload value","rules":[{"t":"set","p":"payload","pt":"msg","to":"req.params.value","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":790,"y":340,"wires":[["5ac90e03.22da3"]]},{"id":"b71d9143.c03bd","type":"change","z":"fa6372cc.47f92","name":"set topic temp1","rules":[{"t":"set","p":"topic","pt":"msg","to":"temp1","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":560,"y":320,"wires":[["43900e79.98cd8"]]},{"id":"e87114aa.6cd1","type":"change","z":"fa6372cc.47f92","name":"set topic temp2","rules":[{"t":"set","p":"topic","pt":"msg","to":"temp2","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":560,"y":360,"wires":[["43900e79.98cd8"]]},{"id":"783c47fd.8dd58","type":"inject","z":"fa6372cc.47f92","name":"temp source 2","topic":"","payload":"12","payloadType":"num","repeat":"3","crontab":"","once":false,"onceDelay":"1.5","x":380,"y":360,"wires":[["e87114aa.6cd1"]]},{"id":"271dedab.aaa7b2","type":"inject","z":"fa6372cc.47f92","name":"temp source 1","topic":"","payload":"10","payloadType":"num","repeat":"2","crontab":"","once":false,"onceDelay":"1","x":380,"y":320,"wires":[["b71d9143.c03bd"]]},{"id":"a197b84d.6a7338","type":"mqtt out","z":"fa6372cc.47f92","name":"temperature","topic":"domoticz/in","qos":"","retain":"","broker":"7e3561ec.acad","x":1150,"y":280,"wires":[]},{"id":"7e3561ec.acad","type":"mqtt-broker","z":"","name":"Domoticz","broker":"192.168.6.11","port":"8084","clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthRetain":"false","birthPayload":"","closeTopic":"","closeRetain":"false","closePayload":"","willTopic":"","willQos":"0","willRetain":"false","willPayload":""}]
One way to do it would be like this:
This is storing the two temps in flow variables - the first flow initially sets them to a high number so the "min" in "choose lower value" will later work. In this case I've used a change node setting the payload to the JSONata of
$min([$flowContext("temp1"), $flowContext("temp2")])
but there's a few ways you could choose to do it.
Here is the code to try:
[{"id":"6bc2755e.9feb9c","type":"debug","z":"f454a93f.0e89d8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","x":990,"y":340,"wires":[]},{"id":"38bd03eb.f7d06c","type":"change","z":"f454a93f.0e89d8","name":"choose lower value","rules":[{"t":"set","p":"payload","pt":"msg","to":"$min([$flowContext(\"temp1\"), $flowContext(\"temp2\")])\t","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":790,"y":340,"wires":[["6bc2755e.9feb9c"]]},{"id":"9066677f.eb0358","type":"change","z":"f454a93f.0e89d8","name":"store temp1","rules":[{"t":"set","p":"temp1","pt":"flow","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":320,"wires":[["38bd03eb.f7d06c"]]},{"id":"a70c9b2a.e7db58","type":"change","z":"f454a93f.0e89d8","name":"store temp2","rules":[{"t":"set","p":"temp2","pt":"flow","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":360,"wires":[["38bd03eb.f7d06c"]]},{"id":"4bd27616.d022c8","type":"inject","z":"f454a93f.0e89d8","name":"temp source 2","topic":"","payload":"12","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":"1.5","x":370,"y":360,"wires":[["a70c9b2a.e7db58"]]},{"id":"7378dd4f.3825b4","type":"inject","z":"f454a93f.0e89d8","name":"temp source 1","topic":"","payload":"10","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":"1","x":370,"y":320,"wires":[["9066677f.eb0358"]]},{"id":"314eb0ec.85211","type":"inject","z":"f454a93f.0e89d8","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":true,"onceDelay":0.1,"x":370,"y":260,"wires":[["688646b.138a6b8"]]},{"id":"688646b.138a6b8","type":"change","z":"f454a93f.0e89d8","name":"set to high","rules":[{"t":"set","p":"temp1","pt":"flow","to":"999","tot":"num"},{"t":"set","p":"temp2","pt":"flow","to":"999","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":260,"wires":[[]]}]
Timing Advance in GSM
I have a bunch of questions concerning Timing Advance in GSM : When is it defined ? Is it the phone or the BTS who's in charge of defining it's value ? is it dynamic, does it depends on certain situations ? Let's say that I figured out a way to get the exact value of the Timing Advance (GSM Layer 1 Transmission level) from the phone's modem : In order to verify my solution, I'm supposed to put my phone over and over in a situation where he have to use/change the Timing Advance while I log its value... How can I do that ? Thanks
In the GSM cellular mobile phone standard, timing advance value corresponds to the length of time a signal takes to reach the base station from a mobile phone. GSM uses TDMA technology in the radio interface to share a single frequency between several users, assigning sequential timeslots to the individual users sharing a frequency. Each user transmits periodically for less than one-eighth of the time within one of the eight timeslots. Since the users are at various distances from the base station and radio waves travel at the finite speed of light, the precise arrival-time within the slot can be used by the base station to determine the distance to the mobile phone. The time at which the phone is allowed to transmit a burst of traffic within a timeslot must be adjusted accordingly to prevent collisions with adjacent users. Timing Advance (TA) is the variable controlling this adjustment. Technical Specifications 3GPP TS 05.10[1] and TS 45.010[2] describe the TA value adjustment procedures. The TA value is normally between 0 and 63, with each step representing an advance of one bit period (approximately 3.69 microseconds). With radio waves travelling at about 300,000,000 metres per second (that is 300 metres per microsecond), one TA step then represents a change in round-trip distance (twice the propagation range) of about 1,100 metres. This means that the TA value changes for each 550-metre change in the range between a mobile and the base station. This limit of 63 × 550 metres is the maximum 35 kilometres that a device can be from a base station and is the upper bound on cell placement distance. A continually adjusted TA value avoids interference to and from other users in adjacent timeslots, thereby minimizing data loss and maintaining Mobile QoS (call quality-of-service). Timing Advance is significant for privacy and communications security, as its combination with other variables can allow GSM localization to find the device's position and tracking the mobile phone user. TA is also used to adjust transmission power in Space-division multiple access systems. This limited the original range of a GSM cell site to 35km as mandated by the duration of the standard timeslots defined in the GSM specification. The maximum distance is given by the maximum time that the signal from the mobile/BTS needs to reach the receiver of the mobile/BTS on time to be successfully heard. At the air interface the delay between the transmission of the downlink (BTS) and the uplink (mobile) has an offset of 3 timeslots. Until now the mobile station has used a timing advance to compensate for the propagation delay as the distance to the BTS changes. The timing advance values are coded by 6 bits, which gives the theoretical maximum BTS/mobile separation as 35km. By implementing the Extended Range feature, the BTS is able to receive the uplink signal in two adjacent timeslots instead of one. When the mobile station reaches its maximum timing advance, i.e. maximum range, the BTS expands its hearing window with an internal timing advance that gives the necessary time for the mobile to be heard by the BTS even from the extended distance. This extra advance is the duration of a single timeslot, a 156 bit period. This gives roughly 120 km range for a cell.[3] and is implemented in sparsely populated areas and to reach islands for example. Hope this Answer the question:)
It's defined everytime the BTS needs to set the define the phone's transmission power, which happens quite often. It's the core system (BTS in GSM) who totally in charge of defining it's value. It's very dynamic, and change a lot. Globally, the GSM core system is constantly trying to find the exact distance between the BTS and the MS, so it constantly make a kind of "ping" to calculate it. The result of such operations is generally not that accurate since there are a lot of obstacles between the mobile and the BTS (it's not a direct link in an open space). Such operations happens a lot, so use your smartphone. Simply.
Contiki OS CC2538: Reducing current / power consumption
I am trying to drive down the current consumption of the contiki os running on the CC2538 development kit. I would like to operate the device from a CR2032 with a run life of 2 years. To achieve this I would need an average current less than 100uA. However when I run the following at 3V, I get the following results: contiki/examples/hello-world = 0.4mA - 2mA contiki/examples/er-rest-example/er-example-client = 27mA contiki/examples/er-rest-example/er-example-server = 27mA thingsquare websocket example = 4mA I have also designed my own target platform based on the cc2538 and get similar results. I have read the guide at https://github.com/contiki-os/contiki/blob/648d3576a081b84edd33da05a3a973e209835723/platform/cc2538dk/README.md and have ensured that in the contiki-conf.h file: - LPM_CONF_ENABLE 1 - LPM_CONF_MAX_PM 2 Can anyone give me some pointers as to how I can get the current down. It would be most appreciated. Regards, Shane
How did you measure the current?
You have to be aware that using a basic ampere meter to measure the current consumption of contiki-os wouldn't give you relevant results. The system is turning on/off the radio at a relative high rate (8Hz by default) in order to perform the CCA. This might not be very easy to catch for an ampere meter.
To have an idea of the current consumption when the device is in deep sleep (and then make calculation to determine the averaged current consumption), I'd rather put the device in the PM state before the program reach the infinite while loop. I used the following code to do that:
lpm_enter();
REG(SYS_CTRL_PMCTL) = SYS_CTRL_PMCTL_PM2;
do { asm("wfi"::); } while(0);
leds_on(LEDS_RED); // should not reach here
while(1){
...
On the CC2538, the CCA check consumes about 10-15mA and last approximately 2ms. When the radio transmit a packet, it consume 25mA. Have a look at this post: Contiki UDP packet transmission duration with CC2538.
Furthermore, to save a little more current, turn off the serial com:
#define CC2538_CONF_QUIET 1
Are you using the SmartRF board? If you want to make proper current measurement with this board, you have to remove every jumpers: P486, P487, P411 and P408. Keep only the jumpers of BTN_SEL and the RESET signals.
Blackberry cache reverse geocode address info with proximity
Most people are limited to about 5 or 6 locations on a daily basis (work, home, school, store, etc). I want to speed up address display by caching a few of these most visited locations. I've been able to get the address info using both google maps GPS and JSON and Locator.reverseGeocode. What would be the best way to cache this information and to check proximity quickly? I found this GPS distance calculation example and have it working. Is there a faster way to check for proximity?
Please see similar question first: Optimization of a distance calculation function There are several things we can change in distance calculations to improve performance: Measure device speed and decrease or increase period of proximity test accordingly Trigonometric calculations takes most of performence, but it may done much faster. First make bold distance calculations using lookup table method, then if distance is less than proximity limit + uncertainty limit, use CORDIC method for more precise calculation. Use constants for Math.PI/180.0 and 180.0/Math.PI several links that may be helpful: Very useful explanations of CORDIC, especially doc from Parallax for dummies Fast transcendent / trigonometric functions for Java Cordic.java at Trac by Thomas B. Preusser Cordic.java at seng440 proj Sin/Cos look-up table source at processing.org by toxi