The NXP LPC845-BRK board is a sub-$6 breadboard friendly development board with an ARM Cortex-M0+ on it. This tutorial is about developing a ‘blinky’ on it using MCUXpresso.

Outline

This tutorial goes through the tool installation and basics of implementing a blinky with MCUXpresso. It should give you a starting point to for your own application on that board.

Installation

For this tutorial we need:

• NXP LPC845-BRK board (see Unboxing the NXP LPC845-BRK Board)
• NXP MCUXpresso IDE (now V10.3.0, see New NXP MCUXpresso IDE V10.3.0 Release)
• NXP MCUXpresso SDK for the LPC845

Download the NXP MCUXpresso IDE from http://www.nxp.com/mcuxpresso/ide and install it with the default options.

Got to http://mcuxpresso.nxp.com/ and select the LPC845 SDK (there is no SDK for the board available yet). I recommend that you configure the SDK with all available software components.

Start the IDE (you can use the default workspace) and import the SDK (zip file) with drag&drop into the ‘Installed SDKs’ view:

New Project

Create a new project:

Select the LPC845 and press Next:

Select the LPC845M301JBD48 for the Device package. Because we are going to use GPIO for the LEDs on the board, make sure that this driver is included. Then press Finish:

With this, we have a blinky project:

LED Pins

Next we configure the pins for the LED on the board. From the schematics we get this information:

• Green on PIO1_0
• Blue on PIO1_1
• Red on PIO1_2

The pins need to be muxed as GPIO output pins. Select the project and open the Pins tool:

Configure PIO1_0, PIO1_1 and PIO1_2 as GPIO pins. The easiest way is to double-click on the GPIO cell entries:

Add Identifiers to the pins, for example LEDG, LEDB and LEDR. We will use #defines created for the pins later in our code:

That’s it. Update the project sources with our changes:

It asks to confirm the changes. Press OK.

Switch back to the Develop Perspective (if not done automatically).

All the settings are stored in a .mex file. I can double-click on that file later to open the settings again:

Ungating Clocks

For the LEDs we are using the GPIO port 1 for which we have to ungate the clocks first, otherwise the GPIO pins won’t work.

Add the following to the includes:

#include "fsl_gpio.h" 

Add the following line to ungate the clocks:

GPIO_PortInit(GPIO, 1); /* ungate the clocks for GPIO_1 */ 

Configuring GPIO Pins

Next we have to configure the GPIO pins as output pins with an initial HIGH (1) value. Add the following configuration to your code:

/* configuration for LOW active GPIO output pin */
static const gpio_pin_config_t configOutput = {
 kGPIO_DigitalOutput,  /* use as output pin */
 1,  /* initial value */
};

And initialize all the pins with that configuration:

/* initialize pins as output pins */
GPIO_PinInit(BOARD_INITPINS_LEDR_GPIO, BOARD_INITPINS_LEDR_PORT, BOARD_INITPINS_LEDR_PIN, &configOutput);
GPIO_PinInit(BOARD_INITPINS_LEDG_GPIO, BOARD_INITPINS_LEDG_PORT, BOARD_INITPINS_LEDG_PIN, &configOutput);
GPIO_PinInit(BOARD_INITPINS_LEDB_GPIO, BOARD_INITPINS_LEDB_PORT, BOARD_INITPINS_LEDB_PIN, &configOutput);

Notice that I’m using the Identifier (LEDG, LEDB and LEDR) in the macros I defined previously in the Pins tool.

Delay

To slow down the LED blinky, add a delay function to the code:

static void delay(void) {
  for(int i=0;i<100000;i++) {
    __asm("nop");
  }
}

Blinky Code

Finally, add some blinky code to the application. The code below will turn on and off each led with a delay in between:

for(;;) { /* blinky, blinky, blinky! */
  /* red */
  GPIO_PortClear(BOARD_INITPINS_LEDR_GPIO, BOARD_INITPINS_LEDR_PORT, 1<<BOARD_INITPINS_LEDR_PIN); /* turn on */
  delay();
  GPIO_PortSet(BOARD_INITPINS_LEDR_GPIO, BOARD_INITPINS_LEDR_PORT, 1<<BOARD_INITPINS_LEDR_PIN);  /* turn off */

  /* green */
  GPIO_PortClear(BOARD_INITPINS_LEDG_GPIO, BOARD_INITPINS_LEDG_PORT, 1<<BOARD_INITPINS_LEDG_PIN); /* turn on */
  delay();
  GPIO_PortSet(BOARD_INITPINS_LEDG_GPIO, BOARD_INITPINS_LEDG_PORT, 1<<BOARD_INITPINS_LEDG_PIN);  /* turn off */

  /* blue */
  GPIO_PortClear(BOARD_INITPINS_LEDB_GPIO, BOARD_INITPINS_LEDB_PORT, 1<<BOARD_INITPINS_LEDB_PIN); /* turn on */
  delay();
  GPIO_PortSet(BOARD_INITPINS_LEDB_GPIO, BOARD_INITPINS_LEDB_PORT, 1<<BOARD_INITPINS_LEDB_PIN);  /* turn off */
} 

Build and Debug

Time to build and then debug it with the board connected:

With the board connected to the host, the IDE automatically recognized the board:

Press OK and the debugger is loading the code:

Run it, and enjoy the blinky-blinky-blinky 🙂

Summary

Although there is no dedicated SDK for the LPC845-BRK board yet, it is very simple and easy to create a blinky application for it. Using the NXP MCUXpresso SDK, IDE and Configuration tools it only needs a few lines in the application code to use the LEDs or any GPIO pins on the board.

List of articles about the LPC845-BRK board:

• Unboxing the NXP LPC845-BRK Board
• Tutorial: Using external Debug Probes with NXP LPC845-BRK Board
• Tutorial: Transforming the NXP LPC845-BRK into a CMSIS-DAP Debug Probe
• Tutorial: Blinky with the NXP LPC845-BRK Board

Happy Transforming 🙂

Links

• LPC845-BRK Board web page: https://www.nxp.com/LPC845Breakout
• User Guide for LPC845-BRK Board: https://www.nxp.com/docs/en/user-guide/UM11181.pdf
• NXP LPC845 web page: https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/lpc-cortex-m-mcus/lpc800-series-cortex-m0-plus-mcus/low-cost-microcontrollers-mcus-based-on-arm-cortex-m0-plus-cores:LPC84X?
• MCUXpresso SDK: http://mcuxpresso.nxp.com/
• MCUXpresso IDE: http://www.nxp.com/mcuxpresso/ide
• MCUXpresso IDE 10.3.0: New NXP MCUXpresso IDE V10.3.0 Release
• List of community projects: https://community.nxp.com/community/lpc/blog/2019/02/02/lpc845-brk-board-projects