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;
}
- // calculat f step
+ // calculate f step
f_step = F_OSC * factor;
do_div(f_step, 524288); // 524288 = 2^19
--
2.25.4
