README.md added.

rpi directory has been renamed to rpi_pico

Author: suikan4github

README.md

@@ -1,2 +1,47 @@
 # duplex-i2s-pico
 An experimental Duplex I2S implementation on PIO and its example applications. 
+
+## Details
+This is an experimental project for the Raspberry Pi Pico I2S implementation. This project targets : 
+- Supports Duplex I2S in Slave mode. 
+- Only 32bit data on I2S is supported. 
+- Supports both RP2040 and RP2350.
+- Unit test by [GoogleTest](https://google.github.io/googletest/) and [fff](https://github.com/meekrosoft/fff).
+- Possible to build on Ubuntu Desktop or WSL. 
+
+## How to obtain this project
+
+The newest copy of this project is found in the [GitHub repository](https://github.com/suikan4github/duplex-i2s-pico). 
+
+
+## Building sample
+All the sample and I2S driver code are under rpi directory. 
+
+See the [rpi/BUILD.md](rpi/BUILD.md)
+## Installing tool
+To build the samples or test, you need to install the build tools on Ubuntu : 
+
+```sh
+apt-get -y update
+apt-get -y install build-essential cmake ninja-build git doxygen
+apt-get -y install gcc-arm-none-eabi libnewlib-arm-none-eabi
+```
+
+## Building test
+The sample program and I2S drivers are tested by GoogleTest and fff. Follow the procedure to build the test. 
+
+From the repository root ( where this README.md stays), run the following commands. 
+```sh
+mkdir build
+cmake -DCMAKE_BUILD_TYPE:STRING=Debug \
+    -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE \
+    -DCMAKE_C_COMPILER:FILEPATH=/usr/bin/gcc \
+    -DCMAKE_CXX_COMPILER:FILEPATH=/usr/bin/g++ \
+    --no-warn-unused-cli \
+    -S . \
+    -B build \
+    -G Ninja
+cmake --build build --config Debug --target all --
+```
+## License.
+This project is provided under [MIT License](LICENSE). 

rpi_pico/BUILD.md

@@ -0,0 +1,45 @@
+# Building the sample for RP2040
+The sample program and I2S drivers are stored in the rpi directory. Follow the procedure to build the test. 
+
+From the repository root ( where this README.md stays), run the following commands. 
+
+```sh
+cd rpi_pico
+
+# Configure the project for Rpi Pico(RP2040)
+cmake -DCMAKE_BUILD_TYPE:STRING=Debug \
+-DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE \
+-DCMAKE_C_COMPILER:FILEPATH=/usr/bin/arm-none-eabi-gcc \
+-DCMAKE_CXX_COMPILER:FILEPATH=/usr/bin/arm-none-eabi-g++ \
+--no-warn-unused-cli \
+-S . \
+-B build \
+-G Ninja
+
+# Build
+cmake --build build --config Debug --target all
+```
+
+# Building the sample for RP2350
+In the case of RP2035, the build procedure should be changed to the followings : 
+
+```sh
+cd rpi_pico
+
+# Configure the project for Rpi Pico(RP2040)
+cmake -DCMAKE_BUILD_TYPE:STRING=Debug \
+-DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE \
+-DCMAKE_C_COMPILER:FILEPATH=/usr/bin/arm-none-eabi-gcc \
+-DCMAKE_CXX_COMPILER:FILEPATH=/usr/bin/arm-none-eabi-g++ \
+--no-warn-unused-cli \
+-DPICO_PLATFORM=rp2350 \
+-DPICO_BOARD=pico2 \
+-S . \
+-B build \
+-G Ninja
+
+# Build
+cmake --build build --config Debug --target all
+```
+
+The PICO_PLATFORM macro and PICO_BOARD macro are added in the configuration phase.