Electronic – Installing a bootloader on an ARM Microcontroller

armbootloadermicrocontroller

I have purchased this LPC1788FBD144,551 MCU and this LPC1313FBD48/01,15 MCU and I want to install a bootloader in assembly on them which can call a function in C. How can I install the bootloader on the ARM MCU? Would I install it directly on the MCU or on a separate component (if so can you show me which part on the newark website)?

Best Answer

Both devices have on-chip bootloaders that will always be executed. With the LPC17xx, you can write a secondary bootloader to execute custom code that will run directly after. You simply need to direct your IDE to place the code at location 0x00.

On the documentation page, have a look at AN11257 and AN11258. These discuss creating secondary bootloaders (SBL) to load code from SPI or I2C respectively. This could retrieve code from a PC or an external memory device.

From AN11257:

In these MCUs, the primary boot loader resides in the boot block. The boot loader is executed every time the part is powered on or reset. It can execute the ISP command handler or the user application code, which is stored in sector 0 of internal flash memory.

The SBL in this project refers to a user-defined application that provides the user with an option to update the User Application Firmware or execute the previously programmed User Application Firmware. It is placed from the address 0x00 so that when the primary boot loader runs user application, it executes first.

I couldn't find similar documentation on the LPC13xx. But it's primary bootloader has a bit more functionality built-in. Specifically the ability to load new programs via UART. Your version lacks the USB functionality they talk about in the User Guide:

The bootloader code is executed every time the part is powered on or reset (see Figure 63). The loader can either execute the ISP command handler or the user application code, or it can obtain the boot image as an attached MSC device through USB. A LOW level during reset at the PIO0_1 pin is considered an external hardware request to start the ISP command handler or the USB device enumeration without checking for a valid user code first. The state of PIO0_3 determines whether the UART or USB interface will be used:

• If PIO0_3 is sampled HIGH, the bootloader connects the LPC134x as a MSC USB device to a PC host. The LPC134x flash memory space is represented as a drive in the host’s Windows operating system.

• If PIO0_3 is sampled LOW, the bootloader configures the UART serial port and calls the ISP command handler.

Remark: On the LPC131x parts (no USB), the state of pin PIO0_3 does not matter.

You can still make the first instructions executed after the primary bootloader act as a custom secondary bootloader. You just need to locate that code at the proper address. How this is done is heavily dependent on your IDE. Refer to your IDE's documentation on how to properly control code placement into the desired sectors.

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