Difference between revisions of "LPC1768: SPI Programming"

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[[category: LPC1768 Tutorials]]
 
[[category: LPC1768 Tutorials]]
−
----
 
 
=Objective=
 
=Objective=
 +
In this tutorial we are going to discuss the SPI ( Serial Peripheral Interface). <br>
 +
After understating the basics of LPC1768 SPI module, We will discuss how to use the Explore Embedded libraries to communicate with any of the SPI devices.
 +
<br><br><br>
 +
 +
 
=LPC1768 SPI Block=
 
=LPC1768 SPI Block=
 
The below block diagram shows the SPI input pins multiplexed with other GPIO pins.<br>
 
The below block diagram shows the SPI input pins multiplexed with other GPIO pins.<br>
 
The SPI pin can be enabled by configuring the corresponding PINSEL register to select  SPI function.<br>
 
The SPI pin can be enabled by configuring the corresponding PINSEL register to select  SPI function.<br>
 
When the SPI function is selected for that pin in the Pin Select register, other Digital signals are disconnected from the SPI input pins.<br>
 
When the SPI function is selected for that pin in the Pin Select register, other Digital signals are disconnected from the SPI input pins.<br>
−
{| class="wikitable" style="text-align:center; background-color:#ABCDEF;margin: 1em auto 1em auto"
+
{| class="table table-striped table-hover table-condensed table-bordered"
−
!Port Pin|| Pin Number || PINSEL_FUNC_0 || PINSEL_FUNC_1 ||PINSEL_FUNC_2 ||PINSEL_FUNC_3
+
|-class="info"
 +
|Port Pin || PINSEL_FUNC_0 || PINSEL_FUNC_1 ||PINSEL_FUNC_2 ||PINSEL_FUNC_3
 
|-
 
|-
−
|P0.15 || 47 || GPIO || TXD1 || SCK0 || <b>SCK</b>
+
|P0.15 || GPIO || TXD1 || SCK0 || <b>SCK</b>
 +
|-class="active"
 +
|P0.16 || GPIO || RXD1 || SSEL0  || <b>SSEL</b>  
 
|-
 
|-
−
|P0.16 || 48 || GPIO || RXD1 || SSEL0  || <b>SSEL</b>  
+
|P0.17 || GPIO || CTS1 || MISO0|| <b>MISO</b>
 +
|-class="active"
 +
|P0.18 || GPIO || DCD1 || MOSI0 || <b>MOSI</b>
 +
|}
 +
<br><br><br><br>
 +
[[File:spi_diagram.png]]
 +
 
 +
=SPI Registers=
 +
 
 +
{| class="table table-striped table-hover table-condensed table-bordered"
 +
|-class="info"
 +
|Register || Description
 
|-
 
|-
−
|P0.17 || 46 || GPIO || CTS1 || MISO0|| <b>MISO</b>
+
|SPCR|| SPI Control Register : used to configure SPI
 +
|-class="active"
 +
|SPSR|| SPI status Register :
 
|-
 
|-
−
|P0.18 || 45 || GPIO || DCD1 || MOSI0 || <b>MOSI</b>
+
|SPDR|| SPI Data Register : contains received data  or data to be transmitted
 +
|-class="active"
 +
|SPCCR|| SPI Clock Counter Register : used to control master SCK frequency
 
|}
 
|}
 +
<br><br>
  
−
=SPI Registers=
+
{| class="table table-striped table-hover table-condensed table-bordered"
 +
|-class="info"
 +
|SPCR
 +
|-
 +
|31:12 || 11:8|| 7 || 6 ||  5 || 4  || 3 || 2 ||1: 0 
 +
|-
 +
| RESERVED || BITS|| SPIE||  LSBF  || MSTR || CPOL  || CPHA || BIT ENABLE || RESERVED
 +
|}
 +
 
 +
'''Bit 1:0 – RESERVED'''<br>
 +
   
 +
'''Bit 2 – BIT ENABLE:'''<br>
 +
This is used to clear the 16-byte Rx FIFO.<br>
 +
0-- .<br>
 +
1-- .<br>
 +
 
 +
'''Bit 3 – CPHA:'''<br>
 +
0-- .<br>
 +
1-- .<br>
 +
 
 +
'''Bit 4 – CPOL:'''<br>
 +
This is used for controlling clock polarity.<br>
 +
0 -- SCK is active high.<br>
 +
1 -- SCK is active low.<br>
 +
 +
'''Bit 5 – MSTR:'''<br>
 +
This bit is used for Master mode select.<br>
 +
0 -- Slave Mode.<br>
 +
1 -- Master Mode.<br>
 +
 
 +
'''Bit 6 – LSBF:'''<br>
 +
0 -- .<br>
 +
1 -- .<br>
 +
 +
'''Bit 4 – SPIE:'''<br>
 +
This bit is used to enable SPI interrupt.<br>
 +
0 -- .<br>
 +
1 -- .<br>
 +
 +
'''Bit 11:8 – BITS:'''<br>
 +
When bit 2 ( BIT ENABLE ) of this register is 1, this field controls the number of bits per transfer:<br>
 +
1000 -- 8 Bits per transfer<br>
 +
1001 -- 9 Bits per transfer<br>
 +
1010 -- 10 Bits per transfer<br>
 +
1011 -- 11 Bits per transfer<br>
 +
1100 -- 12 Bits per transfer<br>
 +
1101 -- 13 Bits per transfer<br>
 +
1110 -- 14 Bits per transfer<br>
 +
1111 -- 15 Bits per transfer<br>
 +
0000 -- 16 Bits per transfer<br>
 +
 
 +
'''Bit 31:12 – RESERVED'''<br>
 +
<br><br>
  
−
{| class="wikitable" style="text-align:left; background-color:#ABCDEF;"
+
{| class="table table-striped table-hover table-condensed table-bordered"
−
!Register || Description
+
|-class="info"
 +
|SPSR
 
|-
 
|-
−
|SPCR|| SPI Control Register
+
|31:8|| 7 || 6 ||  5 || 4  || 3 || 2 : 0 
 
|-
 
|-
−
|SPSR|| Contains the data to be transmitted : used to configure SPI
+
| RESERVED || SPIF  || WCOL || ROVR  || MODF || ABRT || RESERVED
 +
|}
 +
 
 +
'''Bit 2:0 – RESERVED'''<br>
 +
'''Bit 3 – ABRT:'''<br>
 +
'''Bit 4 – MODF:'''<br>
 +
'''Bit 5 – ROVR:'''<br>
 +
'''Bit 6 – WCOL:'''<br>
 +
'''Bit 7 – SPIF:'''<br>
 +
'''Bit 31:8 – RESERVED:'''<br>
 +
<br><br>
 +
 
 +
{| class="table table-striped table-hover table-condensed table-bordered"
 +
|-class="info"
 +
|SPDR
 
|-
 
|-
−
|SPDR|| SPI Data Register : contains received data or data to be transmitted
+
|31:16 || 15:8 || 7: 0  
 
|-
 
|-
−
|SPCCR|| SPI Clock Counter Register : used to control master SCK frequency
+
| RESERVED || Data High || Data Low
 
|}
 
|}
 +
 +
'''Bit 7:0 –  Data Low : '''<br>   
 +
'''Bit 15:8 – Data High :'''<br>
 +
'''Bit 31:16 – RESERVED'''<br>
 
<br><br>
 
<br><br>
  
−
=SPI Register Configuration=
+
{| class="table table-striped table-hover table-condensed table-bordered"
 +
|-class="info"
 +
|SPCCR
 +
|-
 +
|31:8|| 7 : 0 
 +
|-
 +
| RESERVED || COUNTER
 +
|}
 +
 
 +
'''Bit 7:0 – COUNTER :'''<br>
 +
'''Bit 31:8 – RESERVED'''<br>
 +
 
 
=Steps for using SPI=
 
=Steps for using SPI=
 
===Initialize SPI===
 
===Initialize SPI===

Latest revision as of 20:20, 14 April 2016

Objective

In this tutorial we are going to discuss the SPI ( Serial Peripheral Interface).
After understating the basics of LPC1768 SPI module, We will discuss how to use the Explore Embedded libraries to communicate with any of the SPI devices.



LPC1768 SPI Block

The below block diagram shows the SPI input pins multiplexed with other GPIO pins.
The SPI pin can be enabled by configuring the corresponding PINSEL register to select SPI function.
When the SPI function is selected for that pin in the Pin Select register, other Digital signals are disconnected from the SPI input pins.

Port Pin PINSEL_FUNC_0 PINSEL_FUNC_1 PINSEL_FUNC_2 PINSEL_FUNC_3
P0.15 GPIO TXD1 SCK0 SCK
P0.16 GPIO RXD1 SSEL0 SSEL
P0.17 GPIO CTS1 MISO0 MISO
P0.18 GPIO DCD1 MOSI0 MOSI





Spi diagram.png

SPI Registers

Register Description
SPCR SPI Control Register : used to configure SPI
SPSR SPI status Register :
SPDR SPI Data Register : contains received data or data to be transmitted
SPCCR SPI Clock Counter Register : used to control master SCK frequency



SPCR
31:12 11:8 7 6 5 4 3 2 1: 0
RESERVED BITS SPIE LSBF MSTR CPOL CPHA BIT ENABLE RESERVED

Bit 1:0 – RESERVED

Bit 2 – BIT ENABLE:
This is used to clear the 16-byte Rx FIFO.
0-- .
1-- .

Bit 3 – CPHA:
0-- .
1-- .

Bit 4 – CPOL:
This is used for controlling clock polarity.
0 -- SCK is active high.
1 -- SCK is active low.

Bit 5 – MSTR:
This bit is used for Master mode select.
0 -- Slave Mode.
1 -- Master Mode.

Bit 6 – LSBF:
0 -- .
1 -- .

Bit 4 – SPIE:
This bit is used to enable SPI interrupt.
0 -- .
1 -- .

Bit 11:8 – BITS:
When bit 2 ( BIT ENABLE ) of this register is 1, this field controls the number of bits per transfer:
1000 -- 8 Bits per transfer
1001 -- 9 Bits per transfer
1010 -- 10 Bits per transfer
1011 -- 11 Bits per transfer
1100 -- 12 Bits per transfer
1101 -- 13 Bits per transfer
1110 -- 14 Bits per transfer
1111 -- 15 Bits per transfer
0000 -- 16 Bits per transfer

Bit 31:12 – RESERVED


SPSR
31:8 7 6 5 4 3 2 : 0
RESERVED SPIF WCOL ROVR MODF ABRT RESERVED

Bit 2:0 – RESERVED
Bit 3 – ABRT:
Bit 4 – MODF:
Bit 5 – ROVR:
Bit 6 – WCOL:
Bit 7 – SPIF:
Bit 31:8 – RESERVED:


SPDR
31:16 15:8 7: 0
RESERVED Data High Data Low

Bit 7:0 – Data Low :
Bit 15:8 – Data High :
Bit 31:16 – RESERVED


SPCCR
31:8 7 : 0
RESERVED COUNTER

Bit 7:0 – COUNTER :
Bit 31:8 – RESERVED

Steps for using SPI

Initialize SPI

Send Data

Receive Data

Code

Example 1

Using Explore Embedded Libraries

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