Update readme of nrf examples

And also fix `flash` target for nrf51

PUBLISHED_FROM=decc6242380eb7070bfbcb26c57780e756588cc3

examples/nRF51/README.md

@@ -3,8 +3,19 @@
 This is a Mongoose "Hello, world" that can be compiled under nRF51 IoT SDK.
 
 To make it work, you should download [nRF51 IoT SDK](http://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF51-IoT-SDK)
-and unpack it in the current directory as `nrf51_iot_sdk`.
+and unpack it in the current directory as `nrf51_iot_sdk` (so that
+`nrf51_iot_sdk` contains `components`, `external`, etc).
+
+In order to build it with the provided Makefile and ARM GCC, you also need to
+edit the file `nrf51_iot_sdk/components/toolchain/gcc/Makefile.posix` (or
+`Makefile.windows` if you use Windows) : adjust arm-none-eabi path and version
+accordingly to your installation.
 
 The project structure replicates that of the examples provided with the SDK:
 Keil uVision project is located at `boards/pca10028/arm5_no_packs`, ARM-GCC
 Makefile is located in `boards/pca10028/armgcc`..
+
+E.g. in order to build it with ARM GCC, navigate to
+`http/boards/pca10028/armgcc` and type `make`. In order to flash: `make flash`.
+
+For details, refer to an [article on Hackster](https://www.hackster.io/dfrank/mongoose-embedded-networking-library-on-nrf51-and-nrf52-547b15).

examples/nRF51/http/boards/pca10028/armgcc/Makefile

@@ -266,8 +266,8 @@ clean:
 cleanobj:
 	$(RM) $(BUILD_DIRECTORIES)/*.o
 
-flash: $(MAKECMDGOALS)
+flash: nrf51422_xxac_s1xx_iot
 	@echo Flashing: $(OUTPUT_BINARY_DIRECTORY)/$<.hex
-	nrfjprog --reset --program $(OUTPUT_BINARY_DIRECTORY)/$<.hex
+	nrfjprog --reset --program $(OUTPUT_BINARY_DIRECTORY)/$<.hex -f nrf51 --sectorerase
 
 ## Flash softdevice

examples/nRF51/nrf51_iot_sdk/README.md

-Please download the [nRF51 IoT SDK](http://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF51-IoT-SDK) and unpack it into this directory.
+Please download the [nRF51 IoT SDK](http://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF51-IoT-SDK)
+and unpack it into this directory, so that it contains `components`, `external`, etc.

examples/nRF52/README.md

@@ -3,8 +3,19 @@
 This is a Mongoose "Hello, world" that can be compiled under nRF IoT SDK.
 
 To make it work, you should download [nRF5 IoT SDK](http://developer.nordicsemi.com/nRF5_IoT_SDK/)
-and unpack it in the current directory as `nrf5_iot_sdk`.
+and unpack it in the current directory as `nrf5_iot_sdk` (so that
+`nrf5_iot_sdk` contains `components`, `external`, etc).
+
+In order to build it with the provided Makefile and ARM GCC, you also need to
+edit the file `nrf5_iot_sdk/components/toolchain/gcc/Makefile.posix` (or
+`Makefile.windows` if you use Windows) : adjust arm-none-eabi path and version
+accordingly to your installation.
 
 The project structure replicates that of the examples provided with the SDK:
 Keil uVision project is located at `boards/pca10040/arm5_no_packs`; ARM-GCC
 Makefile is located in `boards/pca10040/armgcc`.
+
+E.g. in order to build it with ARM GCC, navigate to
+`http/boards/pca10040/armgcc` and type `make`. In order to flash: `make flash`.
+
+For details, refer to an [article on Hackster](https://www.hackster.io/dfrank/mongoose-embedded-networking-library-on-nrf51-and-nrf52-547b15).

examples/nRF52/nrf5_iot_sdk/README.md

-Please download the [nRF5 IoT SDK](http://developer.nordicsemi.com/nRF5_IoT_SDK/) and unpack it into this directory.
+Please download the [nRF5 IoT SDK](http://developer.nordicsemi.com/nRF5_IoT_SDK/)
+and unpack it into this directory, so that it contains `components`,
+`external`, etc.