Hello Paulo,
thanks for your patch.
On Mon, Jan 03, 2022 at 09:11:35PM +1300, Paulo Miguel Almeida wrote:
> rf69 datasheet states that frequency deviation must exceed 600 Hz but
> also that frequency deviation + (bitrate / 2) should be less than equal
> to 500 kHz to ensure proper modulation.
>
> This patch validates that both conditions are met so RF intersymbol
> interference is "avoided" where possible.
>
> Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@xxxxxxxxx>
> ---
> drivers/staging/pi433/rf69.c | 20 ++++++++++++++++----
> 1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/pi433/rf69.c b/drivers/staging/pi433/rf69.c
> index e62e61ef4d27..cc22915fd489 100644
> --- a/drivers/staging/pi433/rf69.c
> +++ b/drivers/staging/pi433/rf69.c
> @@ -255,17 +255,29 @@ int rf69_set_deviation(struct spi_device *spi, u32 deviation)
> int retval;
> u64 f_reg;
> u64 f_step;
> + u32 bit_rate_reg;
> + u32 bit_rate;
> u8 msb;
> u8 lsb;
> u64 factor = 1000000; // to improve precision of calculation
>
> - // TODO: Dependency to bitrate
> - if (deviation < 600 || deviation > 500000) {
> - dev_dbg(&spi->dev, "set_deviation: illegal input param");
> + // calculate bit rate
> + bit_rate_reg = rf69_read_reg(spi, REG_BITRATE_MSB) << 8;
> + bit_rate_reg |= rf69_read_reg(spi, REG_BITRATE_LSB);
> + bit_rate = F_OSC / bit_rate_reg;
> +
> + /*
> + * frequency deviation must exceed 600 Hz and but not exceed
> + * 500kHz when taking bitrate dependency into consideration
> + * to ensure proper modulation
> + */
> + if (deviation < 600 || (deviation + (bit_rate / 2)) > 500000) {
> + dev_dbg(&spi->dev,
> + "set_deviation: illegal input param: %u", deviation);
> return -EINVAL;
> }
this should go in a separate patch IMO
>
> - // calculat f step
> + // calculate f step
> f_step = F_OSC * factor;
> do_div(f_step, 524288); // 524288 = 2^19
>
> --
> 2.25.4
>
>
thank you,
fabio
