Description

Class definition header for the MicrochipSRAM class. This library allows reading from and writing to any of the Microchip family of Serial SRAM and Serial NVSRAM memory chips. The list can be found at Microchip's page at http://www.microchip.com/design-centers/memory/serial-sram-serial-nvsram/overview.

The most recent version of the library is at https://github.com/Zanduino/MicrochipSRAM/archive/master.zip, the library and sample program descriptions can be found at https://github.com/Zanduino/MicrochipSRAM

At the time of coding this library, the following memories can be used: 23x640 (64Kbit), 23x256 (256Kbit), 23x512 (512Kbit), 23xx1024 (1Mbit), 23LCV512 (512Kbit) and 23LCV1024 (1Mbit).

The memory has 3 operating modes: byte, (32-byte) Page and sequential. All read or write command are started by pulling the SPI CS/SS pin low and sending 2 or 3 address bytes (depending upon which memory is being used) and then either the data is sent to the memory or read from it starting at that address. The default power-on mode is the byte mode, where only one byte is transmitted. The next mode, page, will transmit data within the 32-Byte page, wrapping around to the beginning of the page when the end is reached. The last mode, sequential, ignores page boundaries and reads/writes sequentially until the last memory position is reached, whereupon it wraps around to the beginning again.

This library switches the memory to use sequential mode in order to simplify and speed up data transfer

Instantiating the class involves turning on SPI for the CS/SS pin passed in, and then performing some read and write operations to determine which memory is actually being used. First, a test to see whether 2 or 3 address bytes are used. Only the 1Mbit chips use 3 address bytes, but if 2 address bytes are in use then two bytes are written to the last address, and if the first byte of the chip has a changed value then we know we've gotten a wraparound and have determined the memory size. If the first byte hasn't changed, then the actual memory has to be a larger one, and the next possible size is tested.

configuration

This library is built with the standard "Doxyfile", which is located at https://github.com/Zanduino/Common/blob/main/Doxygen. As described on that page, there are only 5 environment variables used, and these are set in the project's actions file, located at https://github.com/Zanduino/MicrochipSRAM/blob/master/.github/workflows/ci-doxygen.yml Edit this file and set the 5 variables: PRETTYNAME, PROJECT_NAME, PROJECT_NUMBER, PROJECT_BRIEF and PROJECT_LOGO so that these values are used in the doxygen documentation. The local copy of the doxyfile should be in the project's root directory in order to do local doxygen testing, but the file is ignored on upload to GitHub.

clang-format

Part of the GitHub actions for CI is running every source file through "clang-format" to ensure that coding formatting is done the same for all files. The configuration file ".clang-format" is located at https://github.com/Zanduino/Common/tree/main/clang-format and this is used for CI tests when pushing to GitHub. The local file, if present in the root directory, is ignored when committing and uploading.

GNU General Public License v3.0

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Author

Written by Arnd Arnd@.nosp@m.Zand.nosp@m.uino..nosp@m.Com at https://www.github.com/SV-Zanshin

Changelog

Version	Date	Developer	Comments
1.0.6	2020-12-28	SV-Zanshin	Reformatted again
1.0.6	2020-12-02	SV-Zanshin	Reformatted for clang-format
1.0.5	2019-05-28	SV-Zanshin	Issue #2 - corrected misleading comments
1.0.5	2019-01-26	SV-Zanshin	Issue #1 - converted documentation to doxygen
1.0.4	2018-06-25	SV-Zanshin	Minor changes
1.0.3	2017-07-31	SV-Zanshin	Only function prototypes may contain default values / optional parameter declarations, functions may not as this can cause compiler errors
1.0.2	2016-11-20	SV-Zanshin	Constructor uses CS/SS pin, made "SRAMBytes" public
1.0.1	2016-11-19	SV-Zanshin	Added method "clearMemory"
1.0.0	2016-11-19	SV-Zanshin	Cleaned up, https://github.com/Zanduino/MicrochipSRAM
1.0.b1	2016-11-16	SV-Zanshin	Created class