Revision 0:d049f6422506, committed 2011-03-04

Comitter:

marcelvandekamp

Date:

Fri Mar 04 15:22:24 2011 +0000

Commit message:

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Ser23K256.cpp	Fri Mar 04 15:22:24 2011 +0000
@@ -0,0 +1,84 @@
+/* Ser23K256 - drive the Microchip 23K256 SRAM using SPI
+* Copyright (c) 2010 Romilly Cocking
+* Released under the MIT License: http://mbed.org/license/mit
+*/
+
+#include "mbed.h"
+#include "Ser23K256.h"
+
+Ser23K256::Ser23K256(SPI& spi, PinName ncs) : _spi(spi), _ncs(ncs)  {
+    deselect();
+}
+
+void Ser23K256::select() {
+    _ncs = 0;
+}
+
+void Ser23K256::deselect() {
+    _ncs = 1;
+}
+
+void Ser23K256::writeStatus(char status) {
+    select();
+    _spi.write(WRITE_STATUS);
+    _spi.write(status);
+    deselect();
+}
+
+char Ser23K256::readStatus() {
+    select();
+    _spi.write(READ_STATUS);
+    char result = (char) _spi.write(0);
+    deselect();
+    return result;
+}
+
+void Ser23K256::prepareCommand(char command, int address) {
+    select();
+    _spi.write(command);
+    _spi.write(address >> 8);
+    _spi.write(address & 0xFF);
+}
+
+// write or read a single byte
+
+void Ser23K256::write(int address, char byte) {
+    prepareCommand(WRITE, address);
+    _spi.write(byte);
+    deselect();
+}
+
+char Ser23K256::read(int address) {
+    prepareCommand(READ, address);
+    int result = _spi.write(0);
+    deselect();
+    return (char) result;
+}
+
+// buffered write and read
+
+/*
+* the single-byte read and write assume the 23K256 is in its default byte-mode
+* so sequential-model commands must switch the chip into sequential mode
+* at the start and return it to byte mode at the end.
+*/
+
+void Ser23K256::write(int address, char * buffer, int count) {
+    writeStatus(SEQUENTIAL_MODE);
+    prepareCommand(WRITE, address);
+    for (int i = 0; i < count; i++) {
+        _spi.write(buffer[i]);
+    }
+    deselect();
+    writeStatus(BYTE_MODE);
+}
+
+void Ser23K256::read(int address, char * buffer, int count) {
+    writeStatus(SEQUENTIAL_MODE);
+    prepareCommand(READ, address);
+    for (int i = 0; i < count; i++) {
+        buffer[i] = _spi.write(0);
+    }
+    deselect();
+    writeStatus(BYTE_MODE);
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Ser23K256.h	Fri Mar 04 15:22:24 2011 +0000
@@ -0,0 +1,108 @@
+/** Ser23K256 - drive the Microchip 23K256 SRAM using SPI
+* Copyright (c) 2010 Romilly Cocking
+* Released under the MIT License: http://mbed.org/license/mit
+*
+* 23K256 data sheet at http://ww1.microchip.com/downloads/en/DeviceDoc/22100B.pdf
+*
+* Page-mode commands have not been implemented; I have found no need for them yet.
+*
+* Assumes spi mode is default (8,0).
+*
+* You can clock the 23K256 at up to 20MHz, so it supports the mbed's maximum SPI frequency of 12MHz.
+*/
+
+#include "mbed.h"
+
+#ifndef  SER23K256_H
+#define  SER23K256_H
+
+// mode codes for 23K256
+#define BYTE_MODE       0x00
+#define SEQUENTIAL_MODE 0x40
+
+// command codes for 23K256
+#define READ            0x03
+#define WRITE           0x02
+#define READ_STATUS     0x05 // called RDSR in datasheet
+#define WRITE_STATUS    0x01 // called WRSR in datasheet
+
+/** An interface for the Microchip 32k byte 23K256 SRAM over SPI
+*
+* 
+*
+* @code
+* #include "mbed.h"
+* #include "Ser23K256.h"
+*
+*
+* SPI spi(p5,p6,p7);
+* Ser23K256 sram(spi,p14);
+*
+* int main() {
+*   char buff[50];
+*   sram.write(0, 'h');
+*   sram.write(1, 'i');
+*   sram.write(2, '!');
+*   sram.write(3, '\0');
+*   for (int address = 0; address < 4; address++) {
+*       buff[address] = sram.read(address);
+*   }
+*   printf("sram = %s\r\n", buff);
+*   sram.write(0, "Hello world!",12);
+*   sram.read(0, buff, 12);
+*   buff[12]='\0';
+*   printf("now = %s\r\n", buff);
+*}
+* @endcode
+* connections:
+* chip pin 1 to mbed ncs (see below)
+* chip pin 2 SO to mbed MISO
+* chip pin 3 - no connection
+* chip pin 4 to mbed Gnd
+* chip pin 5 SI pin to mbed MOSI
+* chip pin 6 SCK to mbed sck 
+* chip pin 7 (notHOLD) to mbed Vout
+* chip pin 8 to mbed Vout
+*/
+class Ser23K256 {
+public:
+/** Create an interface
+*
+*
+* @param spi   An SPI object
+* @param ncs   Not chip select pin - any free Digital pin will do
+*/
+    Ser23K256(SPI& spi, PinName ncs);
+/** read a byte from SRAM
+* @param address    The address to read from
+* @return the character at that address
+*/
+    char read(int address);
+/** read multiple bytes from SRAM into a buffer
+* @param address    The SRAM address to read from
+* @param buffer     The buffer to read into (must be big enough!)
+* @param count      The number of bytes to read
+*/
+    void read(int address, char * buffer, int count);
+/** write a byte to SRAM
+* @param address    The address SRAM to write to
+* @param byte       The byte to write there
+*/
+    void write(int address, char byte);
+    /** write multiple bytes to SRAM from a buffer
+* @param address    The SRAM address write to
+* @param buffer     The buffer to write from
+* @param count      The number of bytes to write
+*/
+    void write(int address, char * buffer, int count);
+private:
+    SPI& _spi;
+    DigitalOut _ncs;
+    char readStatus();
+    void writeStatus(char status);
+    void prepareCommand(char command, int address);
+    void select();
+    void deselect();
+};
+
+#endif