nRF24LE1 PWM frequency setting

[Kevin]

Hi,

I'm asking this becase it is not very clear about the PWM in Product Specification v1.6 for nRF24LE1
in the nRF24LE1_PS_v1.6.pdf mentioned the pwm Frequency-range from 4 kHz to 254 kHz (when MCU is clocked at 16 MHz), First, may i know what the pre-scale value we chose to get the 4 kHz and 254kHz?

second, what is the available value for PWMCON bit5-2: PWM frequency pre-scale factor , is it from 0~15 ? all the 16 values can be chose ?

Please kindly advise, thank you ~

[Håkon Alseth]

Hi,

 

First, may i know what the pre-scale value we chose to get the 4 kHz and 254kHz?

4kHz: PWMCON (7:6) = 0b'11, and PWMCON[5:2]  = 15

This gives 16M clk * 1 / (255 * (15+1) = ~4 kHz (generating an effective 2kHz pulse)

 

254 kHz: 4kHz: PWMCON (7:6) = 0b'00, and PWMCON[5:2]  = 0

16M * 1 / (31 * (0 + 1) = ~516 kHz (generating an effective ~258 kHz pulse)

 

Quick test in firmware:

    // Fast
    #if 1
    PWMCON = 0x03;
    PWMDC0 = 15;
    // Slow
    #else
    PWMCON = 0xff;
    PWMDC0 = 127;
    #endif

 

So, the documentation is incorrect, as the PWM peripheral itself will be between 4 kHz and 516 kHz, with an effective output frequency of between 2 kHz and 258 kHz.

second, what is the available value for PWMCON bit5-2: PWM frequency pre-scale factor , is it from 0~15 ? all the 16 values can be chose ?

As per the first picture you attached, you can set the prescaler from 0 to 15. You are free to choose any value between.

 

Kind regards,

Håkon

[Kevin]

Hi Hakon,

Very appreciate your answer, that solved my confusion for few days !

please kindly update this in next version PS Doc,  and another errata in my previous post, thanks.

Best Regards,
Kevin.