LeafLabs Garden » Topic: SPI EEPROM 24LC640A status report (working!)

LeafLabs Garden » Topic: SPI EEPROM 24LC640A status report (working!) http://forums.leaflabs.com/topic.php?id=694 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:13:03 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://forums.leaflabs.com/search.php Adam on "SPI EEPROM 24LC640A status report (working!)" http://forums.leaflabs.com/topic.php?id=694#post-3979 Sun, 20 Mar 2011 21:01:45 +0000 Adam 3979@http://forums.leaflabs.com/ Folks, I got some proof-of-concept code for a Microchip 24LC640A 64kb SPI EEPROM working today. Here is a picture of it on a Sparkfun proto shield (you can't see the Maple, but it is underneath the shield): <a href="http://imgur.com/XvrxV" rel="nofollow">http://imgur.com/XvrxV</a> Here is the code: <code> // EEPROM SPI 25LC640 // Demonstrates reading and writing to the EEPROM. // For the Leaf Labs Maple platform. // // Writes a single page (32 bytes), // then reads it back, printing each byte. // // Based on code by Heather Dewey-Hagborg // <a href="http://arduino.cc/en/Tutorial/SPIEEPROM" rel="nofollow">http://arduino.cc/en/Tutorial/SPIEEPROM</a> #define PAGE_SIZE 32 #define SPI_MODE 0 #define CS 10 // chip select // EEPROM opcodes #define WREN 6 #define WRDI 4 #define RDSR 5 #define WRSR 1 #define READ 3 #define WRITE 2 // Use SPI 1: // Pin D11 MOSI // Pin D12 MISO // Pin D13 sck // Pin D10 ss HardwareSPI Spi(1); byte eeprom_output_data; byte eeprom_input_data=0; int address=0; // data buffer uint8 buffer [PAGE_SIZE]; void fill_buffer() { for (int i=0;i<PAGE_SIZE;i++) { buffer[i]=i; } } void setup() { SerialUSB.begin(); SerialUSB.println("starting..."); pinMode(CS, OUTPUT); digitalWrite(CS, HIGH); // disable Spi.begin(SPI_9MHZ, MSBFIRST, SPI_MODE); // fill buffer with data fill_buffer(); // fill eeprom w/ buffer digitalWrite(CS, LOW); // EEPROM enable Spi.send(WREN); // EEPROM write enable instruction digitalWrite(CS, HIGH); // EEPROM disable delay(10); digitalWrite(CS, LOW); // EEPROM enable Spi.send(WRITE); // EEPROM write instruction address=0; Spi.send((uint8)(address>>8)); //send MSByte address first Spi.send((uint8)(address)); //send LSByte address // write PAGE_SIZE bytes for (int i=0;i<PAGE_SIZE;i++) { Spi.send(buffer[i]); // EEPROM write data byte } digitalWrite(CS, HIGH); // EEPROM disable //wait for eeprom to finish writing delay(3000); SerialUSB.println("write finished."); delay(1000); } byte read_eeprom(int EEPROM_address) { //READ EEPROM int data; digitalWrite(CS, LOW); // EEPROM enable Spi.send(READ); //transmit read opcode Spi.send((uint8)(EEPROM_address>>8)); //send MSByte address first Spi.send((uint8)(EEPROM_address)); //send LSByte address data = Spi.send(0xFF); //get data byte digitalWrite(CS, HIGH); // EEPROM disable return data; } void loop() { eeprom_output_data = read_eeprom(address); SerialUSB.print((int) eeprom_output_data); SerialUSB.println(); address++; if (address == PAGE_SIZE) address = 0; delay(500); // pause for readability } </code> It's based off this example on the Arduino website: <a href="http://arduino.cc/en/Tutorial/SPIEEPROM" rel="nofollow">http://arduino.cc/en/Tutorial/SPIEEPROM</a> The circuit is exactly as described in the article. Here's a link to the Octopart page, with datasheet and pricing: <a href="http://octopart.com/25lc640a-i%2Fp-microchip-7721511" rel="nofollow">http://octopart.com/25lc640a-i%2Fp-microchip-7721511</a> I will eventually turn this into a library; I will let you know when I get that done.