drivers/radio/nrf24l01: Increase startup delay.

According to the datasheet of the NRF240L1 chip, 150 μs startup time
is only acceptable when the chip is clocked externally. Most modules
use crystal, which require 1.5 ms to settle. I think it's okay to
wait more in both cases, for a reliable startup.

Signed-off-by: Marcell Pünkösd <punkosdmarcell@rocketmail.com>

Author: marcsello

Diff for: micropython/drivers/radio/nrf24l01/nrf24l01.py

@@ -227,7 +227,7 @@ def send(self, buf, timeout=500):
     def send_start(self, buf):
         # power up
         self.reg_write(CONFIG, (self.reg_read(CONFIG) | PWR_UP) & ~PRIM_RX)
-        utime.sleep_us(150)
+        utime.sleep_us(1500)  # needs to be 1.5ms
         # send the data
         self.cs(0)
         self.spi.readinto(self.buf, W_TX_PAYLOAD)