NXP Semiconductors LPC1114 Manuale utente

Getting Started with NXP's LPC11XX Cortex-M0 ARM 
Microcontrollers
Introduction
Hardware
Software
Code Example 0:  Toggle a GPIO Pin
Code Example 1:  Read a GPIO Pin
Code Example 2:  Setting Up the Oscillator
Code Example 3:  Transmitting Data Using the UART
Code Example 4:  Receiving Data Using the UART
Code Example 5:  Using the Analog to Digital Converter (ADC)
Code Example 6:  Transmitting with Synchronous Serial Port (SSP/SPI)
Code Example 7:  Setting Up the 16bit Timer for PWM
Code Example 8:  Transmitting with I2C
Author's Note:   
 
Introduction
Many engineers use 8 bit microcontrollers because of their low cost and ease of use.  32 bit microcontrollers generally offer higher performance 
than 8 bit parts, but many believe their cost is significantly higher than bit uCs and that they are more difficult to use than 8 bit parts.  While 32 bit 
parts are generally a little more complicated than 8 bit parts, the cost of 8 and 32 bit parts aren’t that far apart in many cases.  Additionally, the 32 
bit parts offer significantly higher performance.  In other words, give 32 bit parts a chance!
NXP has introduced a very low cost (i.e. often less than $1 in production volumes) line of 32 bit microcontrollers, the LPC111X family.  There are 
several other companies also offering some type of ARM Cortex M0 microcontroller.  NXP was one of the earliest, but Freescale (Kinetis L), ST 
Micro (STM32 F0), and Nuvoton (M051,M058,Mini51,NUC100,NUC122) also have Cortex M0 offerings.  This document will give a brief 
introduction on how to get up and running using NXP's .  The code will work on several other members of the LPC11xx family as well. LPC1114
The assumption inherent in this document is that most engineers follow a fairly similar method of learning when presented with a new 
microcontroller family.  They start by getting a development kit and trying to toggle a pin, transmit/receive with a serial port, read an ADC pin 
etc.  This document will show some very simple examples of how to enable and operate these peripherals.  This will not be exhaustive of every 
operating mode and every peripheral but, it is hoped that it will cover the basics in sufficient detail to allow an engineer to get up and running 
quickly.  Also included are some tips regarding custom design of PCBs using these parts (see example schematic and BOM below in the 
"Hardware" section.
This document is primarily targeted at those who are familiar with 8 bit microcontrollers, but are interested in learning to use a 32 bit part.  It is 
hoped that this document can make getting started with a 32 bit part as painless as possible.  It is realized that this code is very simplistic, and if 
one were going to write production code, there would certainly be other features, such as error checking, that would be needed.  This code is 
provided purely to provide a simplistic “working” example.

Hardware
The examples described in this document will be run on Embedded Artists’ (shown at the top of this wiki page).  It should be notedEA-XPR-002
that from Embedded Artists is identical to from NXP.  So the two part numbers can be used interchangeably.  ThisEA-XPR-002 OM11049,598 
document generally refers to  , but that is just for convenience.  Any example given in this document should work on both boardsEA-XPR-002
using the Code Red Software (discussed below).  This PCB can be used standalone, plugged into a solderless , or it can be pluggedbreadboard
into a dedicated base board such as (shown in Figure 1 below).  The or the  plugs in on top of thisEA-XPR-021 EA-XPR-002  OM11049,598 
baseboard and allows you to use the peripherals of the in an easily measurable/observable way.  Since this page was first built NXPLPC1114
purchased Embedded Artists and has obsoleted the .  So just use the OM11049,598.  All the examples should work exactly theEA-XPR-002
same.
  NXP'sFigure 1: EA-XPR-021
If the (or any other LPC111X device) is being designed into a custom board here are a couple examples of how to connect the part toLPC1114
the programming header (plus part numbers).  This circuit was built and successfully tested with the parts indicated.

 
Ref Des Part Number Digi-Key Part Number Other Options 
U1 LPC1114FBD48/302,1 (NXP) 568-5150-ND  
J1 534237-6 (TE Connectivity) A26420-ND S5444-ND, A35047-ND
Y1 ABM7-12.000MHZ-D-2-Y-T (Abracon) 535-9836-1-ND  
39pF GRM1885C1H390JA01D (Murata) 490-1417-1-ND  
1uF EMK107B7105KA-T (Taiyo Yuden) 587-1241-1-ND  
Figure 2:  Here here are some examples of basic circuits that can be used to get the up and running on a custom board.  It should beLC1114
noted that the connector, J1, has the pins on the left and right side shorted together so 1 and 2 are shorted together as are 3 and 4 etc.  The 
connector, , has the advantage of being very securely attached to the PCB.  Other connector options are shown as well.  A possible5535676-7

mating connector for the three connectors given/shown above is from 3M961108-5604-AR

Figure 3: (TE Connectivity), (TE Connectivity), (Sullins), and (3M) respectively5535676-7 534237-6 PPTC081LGBN-RC 961108-5604-AR

Figure 4

Above (figure 3) is a pictorial example of how the can be used as an inexpensive programmer/debugger. TheOM11049,598 OM11049,598

board can be carefully split in two using a “Dremel” tool, at least that’s how separation was accomplished in this case. Wear safety

glasses! Alternatively, I was told by an NXP applications engineer that some customers have found that an old style paper cutter (see Figure 4)

works very well too. If you don't like the idea of cutting the board, the can be used without physically splitting the PCB in two. ToOM11049,598

prepare for use without sawing it in half, use an “exacto” knife to cut the traces between the two rows of vias that compose J4. Then solder a

vertical connector into the vias on the programmer/debugger side.

Figure 5: Here a split is used as a programmer/debugger with a custom PCB. In this case, is the connector onOM11049,598 961108-5604-AR

the programmer/debugger and is the mating connector on the custom PCB.PPTC081LGBN-RC

Software

All software examples were written in the C programming language using LPCXpresso v4.1.5 [12/12/2011] development system. This

development environment is available free of charge at ; The comments in the codehttp://www.support.code-red-tech.com/CodeRedWiki

examples that have a parenthetical note such as (sec 3.5.14) refer to the NXP's "UM10398 LPC11x/LPC11Cxx User Manual" Rev. 12 - 24

September 2012

Important Note: Many of the software examples below write to a register with a name that begins with "LPC_IOCON...". All of these code

samples have been tested and run on real hardware. However on another custom circuit board the author found that in order to successfully

modify these registers the following piece of code had to be included:

LPC_SYSCON->SYSAHBCLKCTRL |= (1<<16); //enable the clock to the

IOCON block (section 3.5.14)

So if one of the code examples shown here doesn't function correctly. Check and see if one of the "LPC_IOCON..." registers are being

modified. If so, add the line of code above before trying to write to an "LPC_IOCON..." register and see if that fixes the problem. The author

found this to be the solution to a problem experienced when using pin PIO1_1 (pin 34 on the 48 pin QFP part). The pin wouldn't toggle until the

line above was added enabling the clock to the IOCON register. So keep this in mind when using the examples here.

Code Example 0: Toggle a GPIO Pin

This code snippet shows a simple program that was compiled and run on the LPCXpresso board successfully. The program toggles pin 23 on

and off within the infinite while loop. Pin 23 will turn the boards lone LED on and off. For more examples of this type click or (for a plainhere here

text file).

#include "LPC11xx.h"

int main(void) { //Toggle a GPIO (FBD48 pin 23, PIO0_7, controls the

LED on the LPC Expresso PCB)

LPC_SYSCON->SYSAHBCLKCTRL |= (1<<6); //enable clock GPIO (sec

3.5.14)

LPC_IOCON->PIO0_7 &= ~(0x10); //NOT REQUIRED, turn off

pull up (sec 7.4.19)

LPC_GPIO0->DIR |= (1<<7); //set pin direction to

output (sec 12.3.2)

unsigned int i = 0;

while(1){ //infinite loop

LPC_GPIO0->DATA |= (1<<7); //set pin high (sec

12.3.1)

for(i=0; i<0xFFFFF; ++i); //arbitrary delay

LPC_GPIO0->DATA &= ~(1<<7); //set pin low (sec

12.3.1)

for(i=0; i<0xFFFFF; ++i); //arbitrary delay

}

return 0 ;

}

Important Note: The LPC1114 toggles pins rather slowly. If you set the oscillator to a frequency of 48MHz and comment out the two "for" loops

you’ll find that this program will only toggle a pin at around 1MHz. It’s something to be aware of if you are planning to toggle pins in a timing

critical application. Some other NXP chips such the LPC13xx, LPC17xx, LPC23xx, LPC8xx, and some members of the LPC21xx family have

“fast GPIO” that will toggle much faster than the LPC111X parts.

Code Example 1: Read a GPIO Pin

This program reads pin 40 (PIO1_4/AD5) and toggles pin 23 in response to pin 40s state. If pin 40 is high, the pin 23 is set high and vice

versa. Recall that on the board pin 23 is attached to an LED. This LED turns on when pin 23 is high. For more examples ofOM11049,598

reading pins as general purpose inputs click . Note that pin 40 is labelled as "AD5" on the PCB since it serves dual functionhere OM11049,598

as an analog to digital converter input if configured differently.

\#include "LPC11xx.h"

int main(void) {

//Toggle a pin 23 in response to digital voltage change on pin 40

LPC_SYSCON->SYSAHBCLKCTRL |= (1<<6); //enable clock GPIO (sec 3.5.14)

LPC_IOCON->PIO0_7 &= ~(0x10); //NOT NECESSARY, turn off pull up

(sec 7.4.19)

LPC_GPIO0->DIR |= (1<<7); //set pin 23/PIO0_7 direction to

output (sec 12.3.2)

LPC_GPIO1->DIR &= ~(1<<4); //set pin 1_4 (pin 40 of QFP) to

input

//unsigned int i = 0;

while(1){ //infinite loop

if(LPC_GPIO1->DATA & (1<<4)) //check state of pin 40, PIO1_4

(sec 12.3.1)

LPC_GPIO0->DATA |= (1<<7); //set pin high (sec 12.3.1)

else

LPC_GPIO0->DATA &= ~(1<<7); //set pin low (sec 12.3.1)

}

return 0 ;

}

In order to change the state of pin 40 on the board a switch such as may be used in conjunction with the pull up (orOM11049,598 450-1467-ND

pull down) functions of PIO1_4 itself. The default state of the pin is to be pulled up.

Code Example 2: Setting Up the Oscillator

Here is a bit of code that will set the clock generation unit to produce a 48MHz clock from the 12MHz system oscillator and connects this clock to

the ARM Cortex-M0 core. This operation is discussed in the user’s manual primarily in Chapter 3, section 3.4. The block diagram shown in

Figure 8 is particularly useful in understanding the function of the code.

#include "LPC11xx.h"

int main(void) {

//USE EXTERNAL CRYSTAL TO GENERATE INTERNAL SYSTEM CLOCK

LPC_SYSCON->SYSAHBCLKDIV = 0x1; //set clock

divider for core to 1

LPC_SYSCON->MAINCLKSEL &= ~(0x03); //set "main

clock" to IRC oscillator, if not system will lock up when PLL turns off!

(sec. 3.5.11)

LPC_SYSCON->MAINCLKUEN &= ~(1); //write a zero

to the MAINCLKUEN register (sec. 3.5.12), necessary for MAINCLKSEL to

update

LPC_SYSCON->MAINCLKUEN |= 1; //write a one to

the MAINCLKUEN register (sec. 3.5.12), necessary for MAINCLKSEL to update

LPC_SYSCON->SYSPLLCLKSEL = 0x01; //connect system

oscillator to SYSTEM PLL (sec. 3.5.9)

LPC_SYSCON->SYSPLLCLKUEN &= ~(1); //write a zero

to SYSPLLUEN register (sec. 3.5.10), necessary for SYSPLLCLKSEL to update

LPC_SYSCON->SYSPLLCLKUEN |= 1; //write a one to

SYSPLLUEN register (sec. 3.5.10), necessary for SYSPLLCLKSEL to update

LPC_SYSCON->PDRUNCFG |= (1<<7); //power down the

PLL before changing divider values (sec 3.5.35)

LPC_SYSCON->SYSPLLCTRL = 0x23; //set MSEL =

0x00011 and PSEL = 0x01 (sec 3.5.3 and table 46 of sec. 3.11.4.1)

LPC_SYSCON->PDRUNCFG &= ~(1<<7); //power up PLL

after divider values changed (sec. 3.5.35)

while((LPC_SYSCON->SYSPLLSTAT & 1) == 0); //wait for PLL

to lock

LPC_SYSCON->MAINCLKSEL = 0x03; //set system

oscillator to the output of the PLL (sec. 3.5.11)

LPC_SYSCON->MAINCLKUEN &= ~(1); //write a zero

to the MAINCLKUEN register (sec. 3.5.12), necessary for MAINCLKSEL to

update

LPC_SYSCON->MAINCLKUEN |= 1; //write a one to

the MAINCLKUEN register (sec. 3.5.12)

for(;;){ //infinite loop

//your application code here

}

return 0 ;

}

The critical bit of code to keep in mind is this line:

LPC_SYSCON->SYSPLLCTRL = 0x42; //set MSEL = 0x00011 and PSEL = 0x01

(table 46 of sec. 3.11.4.1)

This is where the frequency is actually set. If you look at section 3.5.3 you can see how this value is constructed. In this case, it is 0x23. A value

of 0x23 means that MSEL has a binary value of 0_0011, and PSEL has a binary value of 01. Combined as shown in section 3.5.3 they give a

binary value of 010_0011, or a hex value of 0x23. Table 46 in section 3.11.4.2 gives MSEL and PSEL values for two other frequencies as

well: 0x42 for 36MHz and 0x41 for 24MHz.

If you want to look at the output of the clock directly and you aren’t using pin PIO0_7 (pin 23 on the LQFP48 package), you can port the internal

clock directly to the outside world on this pin. Here’s how one would do it. If this code is inserted at the beginning of main() then you can use

your oscilloscope to look at the clock signal directly.

//CONNECT SYSTEM OSCILLATOR TO CLKOUT PIN: This allows measurement

with o-scope.

LPC_IOCON->PIO0_1 &= 0xFFFFFFF8; //clear FUNC bits

(sec. 7.4.4)

LPC_IOCON->PIO0_1 |= 0x01; //set FUNC bits to

CLKOUT function (sec. 7.4.4)

LPC_GPIO0->DIR |= 0x01; //set CLKOUT pin to

output (sec. 12.3.2)

LPC_SYSCON->CLKOUTCLKSEL = 0x3; //sec. 3.5.21

LPC_SYSCON->CLKOUTUEN = 0; //"CLKOUTUEN" has to

be toggled for "CLKOTUCLKSEL" to accept the value written to it

LPC_SYSCON->CLKOUTUEN = 1; //"CLKOUTUEN" has to

be toggled for "CLKOTUCLKSEL" to accept the value written to it

LPC_SYSCON->CLKOUTDIV = 1; //set divider to 1

(sec. 3.5.23)

Code Example 3: Transmitting Data Using the UART

The program below will transmit a single value, in this case 0x55, over the UART. This is a very simple program that doesn’t use interrupts or

check any of the possible error flags, but it gives an idea of how to set up the device. For different baud rates you can adjust the UARTCLKDIV

value. The “UART Fractional Divider Register” can be used to generate the proper baud rate as well (see section 13.5.15 of the LPC11xx User

Manual).

#include "LPC11xx.h"

int main(void) {

//SET UP UART (sec. 13.2 in datasheet "BASIC CONFIGURATION")

LPC_IOCON->PIO1_7 |= 0x01; //configure UART TXD pin

(sec. 7.4.41)

LPC_SYSCON->SYSAHBCLKCTRL |= (1<<12); //enable clock to UART

(sec. 3.5.14)

LPC_SYSCON->UARTCLKDIV |= 0x9B; //0x9B will give approx.

19.2K baud signal (sec. 3.5.16)

LPC_UART->FCR |= 0x01; //enable UART FIFOs

(necessary for operation) (sec. 13.5.6)

LPC_UART->LCR |= 0x03; //set for 8 bit data

width (sec. 13.5.7)

LPC_UART->TER |= 0x80; //transmit enable (sec.

13.5.16)

unsigned int i = 0;

while(1){ //infinite loop

LPC_UART->THR |= 0x55; //transmit data (sec.

13.5.2)

for(i=0; i < 0xFFFFF; ++i); //simple delay to make

scope readings easier to read

}

return 0 ;

}

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