103 lines
3.2 KiB
C
103 lines
3.2 KiB
C
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// spiram.h
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//
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// Header for a Little Library for accessing SPI RAM chips such as 23K256-I/P
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// using bcm2835 library on Raspberry Pi
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//
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// Author: Mike McCauley
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// Copyright (C) 2018 Mike McCauley
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// This software is part of the bcm2835 library and is licensed under the same conditions
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// $Id: $
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#include <stdbool.h> // bool, true, false
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#ifndef SPIRAM_h
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#define SPIRAM_h
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#define SPIRAM_HOLD_DISABLE 0x1
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#define SPIRAM_MODE_BYTE (0x00 | SPIRAM_HOLD_DISABLE)
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#define SPIRAM_MODE_PAGE (0x80 | SPIRAM_HOLD_DISABLE)
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#define SPIRAM_MODE_STREAM (0x40 | SPIRAM_HOLD_DISABLE)
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#define SPIRAM_MODE_INVALID 0xff
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#define SPIRAM_OPCODE_READ_SR 0x05
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#define SPIRAM_OPCODE_WRITE_SR 0x01
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#define SPIRAM_OPCODE_READ 0x03
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#define SPIRAM_OPCODE_WRITE 0x02
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/* Size of a page in 23K256 */
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#define SPIRAM_PAGE_SIZE 32
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/*
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* This library allows you to read and write data from an external SPI interfaced static ram (SRAM)
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* such as 23K256 (256kbit = 32kByte)
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* Byte and POage modes are supported.
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* Valid addresses are from 0x0000 to 0x7fff
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* Tested on RPI 3 Model B, Raspbian Jessie
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*/
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/*
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* Initialise the spiram library, enables SPI with default divider of
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* BCM2835_SPI_CLOCK_DIVIDER_65536 = 6.1035156kHz on RPI3.
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* You can change the SPI speed after calling this by calling bcm2835_spi_setClockDivider()
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* Returns true on success, false otherwise
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*/
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bool spiram_begin();
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/*
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* Stops using the RPI SPI functions and returns the GPIO pins to their default behaviour.
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* Call this when you have finished using SPI forever, or at the end of your program
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* Returns true on success, false otherwise
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*/
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bool spiram_end();
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/*
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* Read and returns the current value of the SRAM status register
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*/
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uint8_t spiram_read_sr();
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/*
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* Write a new value to the SRAM status register,
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* usually one of SPIRAM_MODE_*
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* You should never need to call this directly. Used internally.
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* Returns true on success, false otherwise
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*/
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bool spiram_write_sr(uint8_t value);
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/*
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* Set the operating mode of the SRAM.
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* Mode is one of SPIRAM_MODE_*. THis is done automatically
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* by the spiram_write_* and spiram_read_* functions, so you would not normally
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* need to call this directly.
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* Returns true on success, false otherwise
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*/
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bool spiram_set_mode(uint8_t mode);
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/*
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* Reads a single byte from the given address and returns it.
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*/
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uint8_t spiram_read_byte(uint16_t address);
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/*
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* Writes a single byte to the given address.
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* Returns true on success, false otherwise
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*/
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bool spiram_write_byte(uint16_t address, uint8_t value);
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/*
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* Reads a whole page of data (32 bytes) from the page starting at the given address.
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* The read data is placed in buf. Be sure that there is enough rom there for it.
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* Caution: if the starting address is not on a page boundary,
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* it will wrap back to the beginning of the page.
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* Returns true on success, false otherwise
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*/
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bool spiram_read_page(uint16_t address, uint8_t *buf);
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/*
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* Writes a whole page of data (32 bytes) to the page starting at the given address.
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* Caution: if the starting address is not on a page boundary,
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* it will wrap back to the beginning of the page.
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* Returns true on success, false otherwise
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*/
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bool spiram_write_page(uint16_t address, uint8_t *buf);
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#endif
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