n-AN36 change the Button to PWM

[Inspectron]

I would like to modificate the LED Button application example. The LED characteristic should stay as it is, only the Button characteristic should be changed. I want to use the button characteristic to send the value of a pwm signal. When the device is in connection, it should always send the value of the pwm signal.

Goal of the changes :

1.)

The button_state value should be send all the time and not only when the button is pressed. I`m not sure, but I think that the button will be detected in the button_event_handler. If my presumption is true, how can I change that the value of the button_state will always be send?

2.)

The value of the button_state should have a range from 0-100 and not only 1 or 0. Where in the code the value of the button_state will be set ?

And do I have to change configuration of the value?

EDIT

main.c

[Stefan Birnir Sverrisson]

Hi

1. I guess a timer function is what you are asking for. A timer will generate interrupts periodically to send PWM value periodically. The easiest way to implement a timer is to use the app_timer library which is very low current. You can see an example of app_timer usage in e.g. the ble_app_bps example in the nRF51 SDK v6.1, look at the timers_init() and applicaiton_timers_start() functions in main. For more accurate timer, use a TIMER peripheral, but that consumes substantially more current.

2. The button_event_handler in the main file in ble_app_lbs is called whenever the button is pressed. You can do the same as the button press does when sending the PWM value, i.e. put the code:

       err_code = ble_lbs_on_button_change(&m_lbs, button_action);
       if (err_code != NRF_SUCCESS &&
           err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
           err_code != NRF_ERROR_INVALID_STATE)
       {
           APP_ERROR_CHECK(err_code);
       }
   

into a timer handler instead of the button handler. The ble_lbs_on_button_change function accepts uint8_t value so you can send values 0-255 to this function, so that should great with PWM value range of 0-100.

Update 5.2.2015 I attach a modified ble_app_lbs example that measures the PWM duty cycle on input pin P0.00 and sends the value over BLE. I basically included into the ble_app_lbs the code from the pwm_analyzer example in nRF51 SDK 6.1.0.

nrf51-ble-app-lbs-SDK6.0_with_pwm_analyzer.zip

Update 2 5.2.2015 To test the example, just create a PWM signal on pin P0.00, I did that with a signal generator. Pressing button does not generate a PWM signal like it did in the pwm_analyzer example. Then connect with a central device and enable services, then you should see the measurements appearing on the central device, i.e. on the button characteristic.

[Stefan Birnir Sverrisson]

What are you having problems with exactly? You should be able to use the functionality in the pwm_analyzer example by simply copying the code into the ble_app_lbs example. Instead of writing the PWM value to PORT1 like in the pwm_analyzer exampe, you call the ble_lbs_on_button_change with the pwm value.

One thing to keep in mind is that the NVIC is blocked by the softdevice so you should use the sd_nvic functions instead when enabling the GPIOTE interrupt. An example of setting a peripheral interrupt when using the softdeivce can be found e.g. here, in line 825. Also when you set the ppi channels you must use the the sd_ppi functions, e.g. sd_ppi_channel_enable_set