From f4fe825650e1eb30ad57963232047606ac034e5c Mon Sep 17 00:00:00 2001 From: Daniel Friesel Date: Mon, 25 Jan 2016 23:29:43 +0100 Subject: refactor I2C class into Storage class. Work-in-progress. --- src/storage.cc | 172 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 172 insertions(+) create mode 100644 src/storage.cc (limited to 'src/storage.cc') diff --git a/src/storage.cc b/src/storage.cc new file mode 100644 index 0000000..f755e0b --- /dev/null +++ b/src/storage.cc @@ -0,0 +1,172 @@ +#include +#include +#include +#include + +#include "storage.h" + +Storage storage; + +/* + * EEPROM data structure ("file system"): + * + * Organized as 64B-pages, all animations/texts are page-aligned. Byte 0 .. + * 255 : storage metadata. Byte 0 contains the number of animations, byte 1 the + * byte offset of the first animation, byte 2 of the second, and so on. + * Byte 256+: texts/animations without additional storage metadata, aligned + * to 64B. So, a maximum of 256-(256/64) = 252 texts/animations can be stored, + * and a maximum of 255 * 64 = 16320 Bytes (almost 16 kB / 128 kbit) can be + * addressed. To support larger EEPROMS, change the metadate area to Byte 2 .. + * 511 and use 16bit page pointers. + * + * The text/animation size is not limited by this approach. + * + * Example: + * Byte 0 = 3 -> we've got a total of three animations + * Byte 1 = 4 -> first text/animation starts at byte 64*4 = 256 + * Byte 2 = 8 -> second starts at byte 64*8 = 512 + * Byte 3 = 9 -> third starts at 64*9 * 576 + * Byte 4 = whatever + * . + * . + * . + * Byte 256ff = first text/animation. Has a header encoding its length in bytes. + * Byte 512ff = second + * Byte 576ff = third + * . + * . + * . + */ + +void Storage::enable() +{ + /* + * Set I2C clock frequency to 100kHz. + * freq = F_CPU / (16 + (2 * TWBR * TWPS) ) + * let TWPS = "00" = 1 + * -> TWBR = (F_CPU / 100000) - 16 / 2 + */ + TWSR = 0; // the lower two bits control TWPS + TWBR = ((F_CPU / 100000UL) - 16) / 2; +} + + +/* + * Send an I2C (re)start condition and the EEPROM address in read mode. Returns + * after it has been transmitted successfully. + */ +void Storage::i2c_start_read() +{ + TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); + while (!(TWCR & _BV(TWINT))); + + // Note: The R byte ("... | 1") causes the TWI momodule to switch to + // Master Receive mode + TWDR = (I2C_EEPROM_ADDR << 1) | 1; + TWCR = _BV(TWINT) | _BV(TWEN); + while (!(TWCR & _BV(TWINT))); +} + +/* + * Send an I2C (re)start condition and the EEPROM address in write mode. + * Returns after it has been transmitted successfully. + */ +void Storage::i2c_start_write() +{ + TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); + while (!(TWCR & _BV(TWINT))); + + TWDR = (I2C_EEPROM_ADDR << 1) | 0; + TWCR = _BV(TWINT) | _BV(TWEN); + while (!(TWCR & _BV(TWINT))); +} + +/* + * Send an I2C stop condition. + */ +void Storage::i2c_stop() +{ + TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); +} + +/* + * Sends len bytes to the EEPROM. Note that this method does NOT + * send I2C start or stop conditions. + */ +// TODO Everything[tm] (error handling and generic code) +int8_t Storage::i2c_send(uint8_t len, uint8_t *data) +{ + uint8_t pos = 0; + + for (pos = 0; pos < len; pos++) { + TWDR = data[pos]; + TWCR = _BV(TWINT) | _BV(TWEN); + while (!(TWCR & _BV(TWINT))); + } + + return pos + 1; +} + +/* + * Receives len bytes from the EEPROM into data. Note that this method does + * NOT send I2C start or stop conditions. + */ +// TODO dito +int8_t Storage::i2c_receive(uint8_t len, uint8_t *data) +{ + uint8_t pos = 0; + + for (pos = 0; pos < len; pos++) { + if (pos == len-1) { + // Don't ACK the last byte + TWCR = _BV(TWINT) | _BV(TWEN); + } else { + // Automatically send ACK + TWCR = _BV(TWINT) | _BV(TWEN) | _BV(TWEA); + } + while (!(TWCR & _BV(TWINT))); + data[pos] = TWDR; + } + + return pos + 1; +} + +/* + * Writes len bytes of data into the EEPROM, starting at byte number pos. + * Does not check for page boundaries yet. + * Includes a complete I2C transaction. + */ +int8_t Storage::i2c_write(uint16_t pos, uint8_t len, uint8_t *data) +{ + uint8_t addr_buf[2]; + + addr_buf[0] = pos >> 8; + addr_buf[1] = pos & 0xff; + + i2c_start_write(); + i2c_send(2, addr_buf); + i2c_send(len, data); + i2c_stop(); + + return 0; // TODO proper return code to indicate write errors +} + +/* + * Reads len bytes of data from the EEPROM, starting at byte number pos. + * Does not check for page boundaries yet. + * Includes a complete I2C transaction. + */ +int8_t Storage::i2c_read(uint16_t pos, uint8_t len, uint8_t *data) +{ + uint8_t addr_buf[2]; + addr_buf[0] = pos >> 8; + addr_buf[1] = pos & 0xff; + + i2c_start_write(); + i2c_send(2, addr_buf); + i2c_start_read(); + i2c_receive(len, data); + i2c_stop(); + + return 0; // TODO proper return code to indicate read/write errors +} -- cgit v1.2.3