Article: SPI on BL602 and ESP32

[Lee, Lup Yuen]

Here's my new article about NuttX SPI on BL602 and ESP32...

https://lupyuen.github.io/articles/spi2

Now that NuttX is talking OK to Semtech SX1262 (LoRa Transceiver), I'll
start porting the LoRaWAN Stack to NuttX. Thanks :-)