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Library to drive the Microchip 23K256 SRAM over SPI.
Diff: Ser23K256.cpp
- Revision:
- 2:f96c3c85aa3b
- Child:
- 3:d2314b1ac797
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Ser23K256.cpp Sun Aug 15 13:06:52 2010 +0000 @@ -0,0 +1,91 @@ +// 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" +#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