When the Wake-on approach is enabled in the configurator / using register PROX_CFG, the following happens.
1. At reset, the device is in look for touch mode, all sensors are scanned at 140 ms (you have configured this parameter to 140 ms in ezclick)
2. If there is a valid touch before state timeout period (which is currently 0 in your configurator, set this to a meaningful value, example 5 seconds), the device enters Active mode. In this mode, the buttons and prox sensor is scanned at the rate of 20 ms (not configurable).
3. If state timeout period expires before a prox event, the device enters look for proximity mode. Here all the buttons are disabled and only the prox sensor scans for every 140 ms (user configurable).
1. Make sure that you are not addressing the slave which causes the device to exit sleep mode and power consumption will still be higher. Use the Host interrupt pin to read the status of the MBR3 device only when there is an interrupt.
2. How are you confirming that the buttons are active during the look for proximity phase. If a proximity event is detected, the device will move to look for touch mode and will start scanning all the buttons
3. I do not see any issues with the ezclick configurator. This could also be do to false triggering of prox sensors due to incorrect tuning. False triggering of prox sensor due to external noise or over-sensitivity can cause the device to enter look for touch mode. One way to test this by making use of the host interrupt pin. Check if you are observing an interrupt in the host / or a low pulse in the HI line even without any human finger near the board.
For more information, read section Low Power Design Considerations from MBR3 CapSense Design Guide.
thanks for the fast response
To 1: I add an logic analyser to i2c and host irq. There I can see that there is no further activity after the keypress which I set as start trigger.
To 2: By the current consumption I can see in which mode the MBR3 is. If I only configure the buttons without proximity sensor, the current consumption is lower.
To 3: I don't mean that there is an issue in ezclik configurator, but I may have an error in my configuration that is causing this phenomenon. What are the settings to make the sensitivity of the proximity sensor as low as possible? So I can check if the MBR3 turns to lower power mode.
1. The proximity sensor always scans with a fixed resolution, therefore the scanning time of the proximity sensor can not be reduced.
2. We recommend to always operate the proximity sensor with 16 bits resolution, setting to lower resolution simply divides the obtained value in software and does not reduce the scanning time.
3. How many buttons are there in your application? Please note that the buttons might be scanning with a reduced resolution (hence reduced scan time) compared to the proximity sensor. This might be seen as hig
4. Please do not change the instantaneous power consumed, only check the average power consumption.
6. You can reduce the average power consumed in the look for proximity mode by increasing the scan period value.
7. Please give us the power numbers for the following cases to understand the issue:
Active mode - Active Current , Sleep Current, Average Current
Look For Proximity Mode - Active Current , Average Current
Also you the CY8CMBR3xxx CapSense Design Toolbox.xlsx attached with the CapSense MBR3 design guide for the expected average power consumption for your configuration.
To 3: in our application there are six buttons plus the proximity
To 4: I compare the average current of our device with diffrent keyboard configurations
To 6: My assumption was: that one proximity sensor consumes significantly less power than six keys with the same scan period. But the power consumption is almost identical.
- If all six buttons enabled and MBR3 is in low power mode avarage current of our device is 1.84mA
- If proximity set as wakeup, only one button is enabled and MBR3 runs in low power mode, avarage current of our device is 1.92mA
If you wisch, I can send you the configuration for both situations.
To 7: I will create a test setup where I can record the times and send you the results.
Thank you in advance
here you get my results:
Unfortunately I have no device with which I can measure the current consumption exactly therefore the values are only a rough direction.
When I run a similar scenario with the MB3R DevKit I also come to the conclusion that I do not get any power savings from the proximity sensor.
Thanks for your help and best regards
This is expected due to the high scan time of proximity sensor. From internal calculations, the hardware scan time of prox sensor is around ~ 5.5 ms. The extra ~0.5 ms could be due to the firmware overhead./ measurement error. If you are very concerned about the power numbers, we highly recommend you to move to low power PSoC 4S devices that offer strict control over power consumption. MBR3 is only a configurable device suited for simple touch applications.