We create a new #NuttX SPI Device Driver ... By copying "dat-31r5-sp.c" to "spi_test_driver.c"

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/drivers/rf/spi_test_driver.c

In our SPI Test Driver: Change all "dat31r5sp" to "spi_test_driver" ... Remember to Preserve Case!

https://github.com/lupyuen/incubator-nuttx/commit/8fee69215163180b77dc9d5b9e7449ebe00ac1cc

Do the same to create the Header File for our #NuttX Driver: spi_test_driver.h

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/include/nuttx/rf/spi_test_driver.h

At #NuttX Startup, register our SPI Test Driver as "/dev/spitest0"

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/boards/risc-v/bl602/bl602evb/src/bl602_bringup.c#L599-L617

Add our SPI Test Driver to #NuttX Kconfig

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/drivers/rf/Kconfig#L22-L27

Our SPI Test Driver for #NuttX appears in "make menuconfig"!

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/drivers/rf/Kconfig#L22-L27

Remember to enable "SPI0" and "SPI Character Driver" in #NuttX ... Or our SPI Test Driver won't start

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/drivers/rf/spi_test_driver.c

Here's what happens when we make a boo-boo and #NuttX won't start

https://gist.github.com/lupyuen/ccfd90125f9a180b4cfb459e8a57b323

Update the Makefile "Make.defs" ... So that #NuttX will build our SPI Test Driver

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/drivers/rf/Make.defs#L33-L37

Build, flash and run #NuttX ... Our SPI Test Driver appears as "/dev/spitest0"! 🎉

https://github.com/lupyuen/incubator-nuttx/blob/newdriver/drivers/rf/spi_test_driver.c

Back to our #NuttX SPI Test App ... Here's how we open the SPI Test Driver and write data

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test/spi_test_main.c

This appears when we run our #NuttX SPI Test App ... Let's study our SPI Test Driver

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test/spi_test_main.c

Every #NuttX Device Driver defines the File Operations for the device ... Here are the open(), close(), read(), write() and ioctl() operations for our SPI Test Driver

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/drivers/rf/spi_test_driver.c#L80-L89

In the write() operation for our #NuttX SPI Test Driver, we 1️⃣ Lock the SPI Bus 2️⃣ Config the SPI Interface 3️⃣ Select the SPI Device 4️⃣ Transfer SPI Data 5️⃣ Deselect and Unlock

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/drivers/rf/spi_test_driver.c#L182-L239

Here's how we configure the #NuttX SPI Interface

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/drivers/rf/spi_test_driver.c#L95-L117

To watch what happens inside #NuttX's SPI Driver for #BL602 ... Turn on SPI Debug Logging

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/arch/risc-v/src/bl602/bl602_spi.c

Now we see every byte transferred by #NuttX's SPI Driver for #BL602!

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/drivers/rf/spi_test_driver.c

How to verify the #NuttX SPI Output? We sniff the #BL602 SPI Bus with a Logic Analyser

https://lupyuen.github.io/articles/spi#appendix-troubleshoot-bl602-spi-with-logic-analyser

In #NuttX the SPI Pins for #BL602 are defined in "board.h" ... MOSI is GPIO 1, MISO is GPIO 0

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/boards/risc-v/bl602/bl602evb/include/board.h#L87-L92

#NuttX's SPI Pins match the #BL602 Reference Manual: MOSI = GPIO 1, MISO = GPIO 0 ... But we're about to witness a BL602 SPI Quirk

https://github.com/bouffalolab/bl_docs/tree/main/BL602_RM/en

Logic Analyser connected to #BL602 shows that MISO and MOSI are swapped! This happens in BL602 IoT SDK ... Also in #NuttX!

https://lupyuen.github.io/articles/spi#spi-data-pins-are-flipped

We can swap MISO and MOSI on #BL602 by setting a Hardware Register ... Let's do this on #NuttX

https://lupyuen.github.io/articles/pinedio#spi-pins-are-swapped

Here's how we swap #BL602 MOSI and MISO on #NuttX ... So that the SPI Pins are consistent with the BL602 Reference Manual

https://github.com/lupyuen/incubator-nuttx/blob/swap_miso_mosi/arch/risc-v/src/bl602/bl602_spi.c#L1080-L1140

After swapping #BL602 MISO and MOSI at #NuttX startup ... Logic Analyser shows that the SPI Pins are now consistent with BL602 Reference Manual! 🎉

https://github.com/lupyuen/incubator-nuttx/blob/swap_miso_mosi/arch/risc-v/src/bl602/bl602_spi.c#L1080-L1140

Let's test #NuttX SPI with #BL602 and Semtech SX1262 LoRa Transceiver

https://www.semtech.com/products/wireless-rf/lora-core/sx1262

We implement the Read Operation for our #NuttX SPI Driver ... So that we can fetch the SPI Response from SX1262

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/drivers/rf/spi_test_driver.c#L210-L233

Our #NuttX App transmits an SPI Command to SX1262 ... And reads the SPI Response from SX1262

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c#L54-L84

#BL602 SPI Chip Select has a problem ... It goes High after EVERY byte ... Which is no-no for SX1262 ... Solution: We control Chip Select via GPIO

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c#L42-L74

Here's our #NuttX App controlling SPI Chip Select via GPIO

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c#L42-L74

Now our #NuttX App is ready to read an SX1262 Register over SPI!

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c#L90-L119

Our #NuttX App reads an SX1262 Register ... But it returns garbage! There's a workaround for this #BL602 SPI Quirk

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c#L90-L119

#BL602 has an SPI Quirk ... We must use SPI Mode 1 instead of Mode 0 ... Let's fix this in #NuttX

https://lupyuen.github.io/articles/spi#spi-phase-looks-sus

For #NuttX on #BL602, we use SPI Mode 1 instead of Mode 0 ... To work around the SPI Mode Quirk

https://github.com/lupyuen/incubator-nuttx/blob/spi_test/drivers/rf/spi_test_driver.c#L51-L57

Our #NuttX App now reads the SX1262 Register correctly! 🎉

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c

Will #NuttX run on #Pine64's PineDio Stack BL604 with onboard Semtech SX1262? Let's find out!

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

Here's how Semtech SX1262 is wired onboard #PineDio Stack #BL604 ... Let's update the Pin Definitions in NuttX

Here are the #NuttX Pin Definitions for PineDio Stack BL604 with onboard SX1262 ... As derived from the schematic

https://github.com/lupyuen/incubator-nuttx/blob/pinedio/boards/risc-v/bl602/bl602evb/include/board.h#L42-L95

Our #NuttX App runs OK on PineDio Stack BL604 with onboard SX1262! 🎉

https://github.com/lupyuen/incubator-nuttx-apps/blob/spi_test/examples/spi_test2/spi_test2_main.c