Clarify README regarding CPU choice
Currently TARGET_CPU should be used to set CPU+features, if
using core_platform provided toolchain files.
Change-Id: I053cc25de12501a2773238820daa150f9ea20fa7
diff --git a/README.md b/README.md
index 5338e8f..d5e68bb 100644
--- a/README.md
+++ b/README.md
@@ -8,8 +8,16 @@
be cross compiled for any of the supported Arm Cortex(R)-M CPUs, which requires
the user to configure the build to match their system configuration.
-One such requirement is to define `CMAKE_SYSTEM_PROCESSOR` for the target CPU,
-for example "cortex-m55+nodsp+nofp". Similarly the target NPU configuration is
+
+One such requirement is to define the target CPU, normally by setting
+`CMAKE_SYSTEM_PROCESSOR`. **Note** that when using the toolchain files provided
+in [core_platform](https://git.mlplatform.org/ml/ethos-u/ethos-u-core-platform.git),
+the variable `TARGET_CPU` must be used instead of `CMAKE_SYSTEM_PROCESSOR`.
+
+Target CPU is specified on the form "cortex-m<nr><features>", for example:
+"cortex-m55+nodsp+nofp".
+
+Similarly the target NPU configuration is
controlled by setting `ETHOSU_TARGET_NPU_CONFIG`, for example "ethos-u55-128".
The build configuration can be defined either in the toolchain file or
@@ -23,6 +31,16 @@
$ cmake --build build
```
+or when using toolchain files from [core_platform](https://git.mlplatform.org/ml/ethos-u/ethos-u-core-platform.git)
+
+```[bash]
+$ cmake -B build \
+ -DCMAKE_TOOLCHAIN_FILE=<core_platform_toolchain> \
+ -DTARGET_CPU=cortex-m<nr><features> \
+ -DETHOSU_TARGET_NPU_CONFIG=ethos-u<nr>-<macs>
+$ cmake --build build
+```
+
## Driver APIs
The driver APIs are defined in `include/ethosu_driver.h` and the related types