Libraries

EA Library

The LPC4088 QuickStart Board contains a number of on-board peripherals which doesn't have a corresponding driver implementation in the mbed SDK. Embedded Artists has developed a separate library with drivers for those peripherals as well as other related components.

• SDRAM initialization
• QSPI File System for the 8 MB QSPI flash (see section "File System on QSPI Flash" below for a more detailed description of this file system).
• MCI File System for MMC/SD card interface
• LCD Controller interface for the LPC4088 on-chip LCD controller
• Driver for Embedded Artists 4.3 inch and 7 inch displays (LCD Board)
• Driver for Texas Instruments TSC2046 touch screen controller. This touch screen is mounted on the 4.3 inch and 7 inch displays.
• A light-weight graphical library based on Adafruit's GFX.

USB Device

The mbed official USB device library has been ported to the LPC4088 QuickStart Board. There are several USB device class implementations available. Please visit the USB device page in the handbook for more details.

The micro-B connector used for USB device is shown in the picture below.

USB Host

The mbed SDK contains a USB host library. Currently this library is NOT supported by the LPC4088 QuickStart Board. The reason is that the implementation mix the use of main SRAM (where stack and heap are located) and peripheral SRAM. On the LPC1768 microcontroller this is okay since the USB Host block has access to both these memory regions. On the LPC4088 microcontroller main SRAM is however not accessible by the USB host block.

The USB host implementation must be modified to only use one memory region in order for it to work on the LPC4088 microcontroller. This is currently being investigated, but there is no date when it is planned to be fixed.

emWin GUI Library

Segger's graphical library emWin can be used free of charge with NXP's microcontrollers. More information about how to use this library can be found on the emWin page.

Memory Model

External SDRAM

The LPC4088 has a SDRAM that must be initialized before use:

#include "mbed.h"
#include "sdram.h"

int main() {
    if (sdram_init()) {
        printf("Failed to initialized SDRAM\n");
    }
}

By default the SDRAM is attached to the heap and thus allowing malloc(), realloc() and free() functions to use it, see the example below.

#include "mbed.h"
#include "sdram.h"

int main (void) {
    void* a, b, c, d, e;
    if (sdram_init() == 1) {
        printf("Failed to initialize SDRAM\n");
        return 1;
    }

    a = malloc(        1024); // will be from internal RAM
    b = malloc(   1024*1024); // will be from SDRAM as it is too large
    c = malloc(15*1024*1024); // will be from SDRAM
    d = malloc(15*1024*1024); // will be from SDRAM
    e = malloc(15*1024*1024); // will fail as there is not enough heap left

    // deallocation goes here...
}

QSPI

The LPC4088 has an SPI Flash Interface (SPIFI) allowing external serial flash memories to be connected with low performance penalties. A driver API included in on-chip ROM handles setup, programming and erasure and after initializing the SPIFI driver, the flash content is accessible as normal memory (in the 0x28000000..0x28ffffff memory range) using byte, halfword, and word accesses by the processor and/or DMA.Programming (i.e. writing data to the flash) is supported for up to 256 bytes at a time (which is the size of a "page" in the flash). Programming means that a bit can either be left at 0, or programmed from 1 to 0. Changing bits from 0 to 1 requires an erase operation.While bits can be individually programmed from 1 to 0, erasing bits from 0 to 1 must be done in larger chunks (manufacturer dependant but typically 4Kbyte to 64KByte at a time).

The SPIFI driver handles flash memories connected via standard SPI as well as Dual I/O and Quad I/O with Quad I/O SPI (or QSPI for short) being the fastest. See the User's Manual for LPC4088 for a list of compatible memories.

The LPC4088 Quick Start Board has 8 MByte of QSPI FLASH from Winbond. This particular memory allows programming of up to 256 bytes at a time and erasing is done in 4KByte blocks.

It is possible to execute code directly from the QSPI FLASH and/or put a file system on it (see next section below).

File System on QSPI Flash

One way to utilize the 8MByte of QSPI FLASH on the LPC4088 QuickStart Board is to place a file system on it. The QSPIFileSystem is using mbed's FileSystemLike interface making using it is as simple as:

#include "mbed.h"
#include "QSPIFileSystem.h"
 
QSPIFileSystem qspifs("qspi");
int main() {
    if (!qspifs.isformatted()) {
        qspifs.format();
    }
    
    FILE* fh = fopen("/qspi/hello.txt", "w");
    if (fh != NULL) {
        fwrite("Hello World!", 12, 1, fh);
        fclose(fh);
    }
}

The file system can be formatted to a specific size in increments of 1MByte and will allways be placed at the top of the address range. For the 8 MByte memory on the LPC4088 QuickStart Board this means:

                        0x28000000                                                0x28800000
                            |------|------|------|------|------|------|------|------|
qspifs.format(1)            |   available for program                        |  FS  |
                            |------|------|------|------|------|------|------|------|

                            |------|------|------|------|------|------|------|------|
qspifs.format(2)            |   available for program                 | FileSystem  |
                            |------|------|------|------|------|------|------|------|

                            |------|------|------|------|------|------|------|------|
qspifs.format(7)            | PROG |                 FileSystem                     |
                            |------|------|------|------|------|------|------|------|

                            |------|------|------|------|------|------|------|------|
qspifs.format(8)            |                       FileSystem                      |
                            |------|------|------|------|------|------|------|------|

The file system must be placed at the top of the memory because the linker scripts places your program at the bottom of the memory (if needed).

Tools

The QSPIFileSystem can be manipulated using one of the two sample apps or by directly downloading one of the prepared image files.

By flashing one of these images you will get an empty file system of the desired size in MBytes as indicated by the last number in the file extension, i.e. qspifs_erase.fs3 will create a 3MByte file system leaving the first 5MBytes of the QSPI free for program download.

The *.fsX files can be drag-n-dropped on the MBED drive in the same way as the *.bin files are. A *.fsX file will not overwrite the program stored in internal flash (if any).