BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

Sigurd — Fri, 17 Feb 2017 11:13:08 GMT

The period = 1/frequency, so for 500 hz, period = 1/500 = 0.002 s = 2000 us

APP_PWM_DEFAULT_CONFIG_1CH(2000L,pin number)

For 300 Hz you need to set the period to 3333L. I think you should be able to drive the buzzer with 3.3V/5V, but you may not get the maximum volume possible. You could also consider using a transistor, see this thread.

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

tyler — Thu, 16 Feb 2017 17:20:04 GMT

@sigurd Alright I couldn't find the data sheet, but on the website I found the following info: "This 75dB Piezo electric buzzer operates on 6VDC, carrying a maximum 45mA current with a tame buzzer tone rating of 300-500Hz.". I assume that means that the frequency is between 300 and 500 hz. What values would I pass to APP_PWM_DEFAULT_CONFIG_1CH() to set this frequency? Also is it a problem if I am using a 6v buzzer with a 5v micro controller?

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

Sigurd — Wed, 15 Feb 2017 14:47:13 GMT

You can set the duty cycle with the app_pwm_channel_duty_set() function, and the period/frequency with the APP_PWM_DEFAULT_CONFIG_1CH()/APP_PWM_DEFAULT_CONFIG_2CH() function. You can vary the volume of the sound by modifying the duty cycle. 0% will produce no sounds, 50% will be the max volume. Between 50% and 100% is the same as between 0% and 50%. Different frequencies will give you different tones.

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

tyler — Wed, 15 Feb 2017 14:01:35 GMT

@sigurd Yes I was looking at the example in \examples\peripheral\pwm. It doesn't do a good job of explaining what each variable does though. Like it doesn't have a variable set for the duty cycle or frequency which I need to know how to set. ..... The peripheral\pwm is actually the example I was previously using when I was having problems..... I think I may have used a pin without PWM but I'm not sure (how do I check if the pin has PWM ability). All I know is that I went in and changed the 'value' variable and the tone and volume of the buzzer was not impacted. How can I go about fixing this?

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

Sigurd — Wed, 15 Feb 2017 13:11:38 GMT

The advantage of using the PWM library is that you get more precise timing on the period the signal is high/low, and therefore get a more stable frequency. The PWM library takes care of all the timing in order to produce a stable frequency. I suspected that this is the reason you get that “awful screeching sound” when not using PWM, and that you are using a frequency that is not resonating well with your buzzer. If you take a look in the buzzer datasheet, the resonance frequency should be listed. If you change the PWM frequency, the tone will change. There is a PWM example in the SDK, have you looked at that?: SDK_folder\examples\peripheral\pwm

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

tyler — Tue, 14 Feb 2017 20:32:55 GMT

@sigurd What is the advantage to using PWM? I tried using it but was unable to get it to work. What was happening was I would change the variables for the PWM and the tone wouldn't be effected at all. Since the behavior was the same as just using a normal write to the gpio and just setting the gpio to high or low was easier I removed the pwm. Do you have a good guide or explanation for how I can get PWM working?

RE: BLE Nano/Nordic SDK: making a quick buzz from a piezo speaker

Sigurd — Tue, 14 Feb 2017 14:13:38 GMT

I would strongly recommend to use the PWM. I see that you have tried this earlier in this post, what is the reason you are not using PWM anymore?