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583 lines
14 KiB
C
583 lines
14 KiB
C
/*
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* ----------------------------------------------------------------------------
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* "THE BEER-WARE LICENSE" (Revision 42):
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* <joerg@FreeBSD.ORG> wrote this file. As long as you retain this notice you
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* can do whatever you want with this stuff. If we meet some day, and you think
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* this stuff is worth it, you can buy me a beer in return. Joerg Wunsch
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* ----------------------------------------------------------------------------
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*/
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/*
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* ----------------------------------------------------------------------------
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* Updated to handle larger devices having 16-bit addresses
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* (2007-09-05) Ruwan Jayanetti
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* ----------------------------------------------------------------------------
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*/
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/* $Id$ */
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/*
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* Simple demo program that talks to a 24Cxx I²C EEPROM using the
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* builtin TWI interface of an ATmega device.
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*/
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#include <inttypes.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <avr/io.h>
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#include <util/twi.h> /* Note [1] */
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#define DEBUG 1
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/*
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* System clock in Hz.
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*/
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#define F_CPU 14745600UL /* Note [2] */
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/*
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* Compatibility defines. This should work on ATmega8, ATmega16,
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* ATmega163, ATmega323 and ATmega128 (IOW: on all devices that
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* provide a builtin TWI interface).
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*
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* On the 128, it defaults to USART 1.
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*/
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#ifndef UCSRB
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# ifdef UCSR1A /* ATmega128 */
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# define UCSRA UCSR1A
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# define UCSRB UCSR1B
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# define UBRR UBRR1L
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# define UDR UDR1
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# else /* ATmega8 */
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# define UCSRA USR
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# define UCSRB UCR
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# endif
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#endif
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#ifndef UBRR
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# define UBRR UBRRL
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#endif
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/*
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* Note [3]
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* TWI address for 24Cxx EEPROM:
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*
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* 1 0 1 0 E2 E1 E0 R/~W 24C01/24C02
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* 1 0 1 0 E2 E1 A8 R/~W 24C04
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* 1 0 1 0 E2 A9 A8 R/~W 24C08
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* 1 0 1 0 A10 A9 A8 R/~W 24C16
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*/
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#define TWI_SLA_24CXX 0xa0 /* E2 E1 E0 = 0 0 0 */
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/*
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* Note [3a]
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* Device word address length for 24Cxx EEPROM
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* Larger EEPROM devices (from 24C32) have 16-bit address
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* Define or undefine according to the used device
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*/
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//#define WORD_ADDRESS_16BIT
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/*
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* Maximal number of iterations to wait for a device to respond for a
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* selection. Should be large enough to allow for a pending write to
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* complete, but low enough to properly abort an infinite loop in case
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* a slave is broken or not present at all. With 100 kHz TWI clock,
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* transfering the start condition and SLA+R/W packet takes about 10
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* µs. The longest write period is supposed to not exceed ~ 10 ms.
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* Thus, normal operation should not require more than 100 iterations
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* to get the device to respond to a selection.
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*/
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#define MAX_ITER 200
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/*
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* Number of bytes that can be written in a row, see comments for
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* ee24xx_write_page() below. Some vendor's devices would accept 16,
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* but 8 seems to be the lowest common denominator.
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*
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* Note that the page size must be a power of two, this simplifies the
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* page boundary calculations below.
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*/
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#define PAGE_SIZE 8
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/*
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* Saved TWI status register, for error messages only. We need to
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* save it in a variable, since the datasheet only guarantees the TWSR
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* register to have valid contents while the TWINT bit in TWCR is set.
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*/
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uint8_t twst;
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/*
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* Do all the startup-time peripheral initializations: UART (for our
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* debug/test output), and TWI clock.
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*/
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void
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ioinit(void)
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{
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#if F_CPU <= 1000000UL
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/*
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* Note [4]
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* Slow system clock, double Baud rate to improve rate error.
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*/
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UCSRA = _BV(U2X);
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UBRR = (F_CPU / (8 * 9600UL)) - 1; /* 9600 Bd */
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#else
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UBRR = (F_CPU / (16 * 9600UL)) - 1; /* 9600 Bd */
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#endif
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UCSRB = _BV(TXEN); /* tx enable */
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/* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
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#if defined(TWPS0)
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/* has prescaler (mega128 & newer) */
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TWSR = 0;
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#endif
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#if F_CPU < 3600000UL
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TWBR = 10; /* smallest TWBR value, see note [5] */
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#else
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TWBR = (F_CPU / 100000UL - 16) / 2;
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#endif
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}
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/*
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* Note [6]
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* Send character c down the UART Tx, wait until tx holding register
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* is empty.
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*/
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int
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uart_putchar(char c, FILE *unused)
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{
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if (c == '\n')
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uart_putchar('\r', 0);
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loop_until_bit_is_set(UCSRA, UDRE);
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UDR = c;
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return 0;
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}
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/*
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* Note [7]
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*
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* Read "len" bytes from EEPROM starting at "eeaddr" into "buf".
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*
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* This requires two bus cycles: during the first cycle, the device
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* will be selected (master transmitter mode), and the address
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* transfered.
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* Address bits exceeding 256 are transfered in the
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* E2/E1/E0 bits (subaddress bits) of the device selector.
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* Address is sent in two dedicated 8 bit transfers
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* for 16 bit address devices (larger EEPROM devices)
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*
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* The second bus cycle will reselect the device (repeated start
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* condition, going into master receiver mode), and transfer the data
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* from the device to the TWI master. Multiple bytes can be
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* transfered by ACKing the client's transfer. The last transfer will
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* be NACKed, which the client will take as an indication to not
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* initiate further transfers.
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*/
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int
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ee24xx_read_bytes(uint16_t eeaddr, int len, uint8_t *buf)
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{
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uint8_t sla, twcr, n = 0;
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int rv = 0;
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#ifndef WORD_ADDRESS_16BIT
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/* patch high bits of EEPROM address into SLA */
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sla = TWI_SLA_24CXX | (((eeaddr >> 8) & 0x07) << 1);
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#else
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/* 16-bit address devices need only TWI Device Address */
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sla = TWI_SLA_24CXX;
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#endif
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/*
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* Note [8]
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* First cycle: master transmitter mode
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*/
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restart:
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if (n++ >= MAX_ITER)
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return -1;
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begin:
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TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send start condition */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
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case TW_REP_START: /* OK, but should not happen */
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case TW_START:
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break;
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case TW_MT_ARB_LOST: /* Note [9] */
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goto begin;
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default:
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return -1; /* error: not in start condition */
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/* NB: do /not/ send stop condition */
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}
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/* Note [10] */
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/* send SLA+W */
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TWDR = sla | TW_WRITE;
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TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
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case TW_MT_SLA_ACK:
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break;
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case TW_MT_SLA_NACK: /* nack during select: device busy writing */
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/* Note [11] */
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goto restart;
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case TW_MT_ARB_LOST: /* re-arbitrate */
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goto begin;
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default:
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goto error; /* must send stop condition */
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}
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#ifdef WORD_ADDRESS_16BIT
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TWDR = (eeaddr >> 8); /* 16-bit word address device, send high 8 bits of addr */
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TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
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case TW_MT_DATA_ACK:
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break;
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case TW_MT_DATA_NACK:
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goto quit;
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case TW_MT_ARB_LOST:
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goto begin;
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default:
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goto error; /* must send stop condition */
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}
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#endif
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TWDR = eeaddr; /* low 8 bits of addr */
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TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
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case TW_MT_DATA_ACK:
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break;
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case TW_MT_DATA_NACK:
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goto quit;
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case TW_MT_ARB_LOST:
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goto begin;
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default:
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goto error; /* must send stop condition */
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}
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/*
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* Note [12]
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* Next cycle(s): master receiver mode
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*/
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TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send (rep.) start condition */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
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case TW_START: /* OK, but should not happen */
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case TW_REP_START:
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break;
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case TW_MT_ARB_LOST:
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goto begin;
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default:
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goto error;
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}
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/* send SLA+R */
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TWDR = sla | TW_READ;
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TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
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case TW_MR_SLA_ACK:
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break;
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case TW_MR_SLA_NACK:
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goto quit;
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case TW_MR_ARB_LOST:
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goto begin;
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default:
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goto error;
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}
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for (twcr = _BV(TWINT) | _BV(TWEN) | _BV(TWEA) /* Note [13] */;
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len > 0;
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len--)
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{
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if (len == 1)
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twcr = _BV(TWINT) | _BV(TWEN); /* send NAK this time */
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TWCR = twcr; /* clear int to start transmission */
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while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
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switch ((twst = TW_STATUS))
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{
|
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case TW_MR_DATA_NACK:
|
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len = 0; /* force end of loop */
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/* FALLTHROUGH */
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case TW_MR_DATA_ACK:
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*buf++ = TWDR;
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rv++;
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if(twst == TW_MR_DATA_NACK) goto quit;
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break;
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default:
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goto error;
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}
|
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}
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quit:
|
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/* Note [14] */
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TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */
|
|
|
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return rv;
|
|
|
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error:
|
|
rv = -1;
|
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goto quit;
|
|
}
|
|
|
|
/*
|
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* Write "len" bytes into EEPROM starting at "eeaddr" from "buf".
|
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*
|
|
* This is a bit simpler than the previous function since both, the
|
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* address and the data bytes will be transfered in master transmitter
|
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* mode, thus no reselection of the device is necessary. However, the
|
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* EEPROMs are only capable of writing one "page" simultaneously, so
|
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* care must be taken to not cross a page boundary within one write
|
|
* cycle. The amount of data one page consists of varies from
|
|
* manufacturer to manufacturer: some vendors only use 8-byte pages
|
|
* for the smaller devices, and 16-byte pages for the larger devices,
|
|
* while other vendors generally use 16-byte pages. We thus use the
|
|
* smallest common denominator of 8 bytes per page, declared by the
|
|
* macro PAGE_SIZE above.
|
|
*
|
|
* The function simply returns after writing one page, returning the
|
|
* actual number of data byte written. It is up to the caller to
|
|
* re-invoke it in order to write further data.
|
|
*/
|
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int
|
|
ee24xx_write_page(uint16_t eeaddr, int len, uint8_t *buf)
|
|
{
|
|
uint8_t sla, n = 0;
|
|
int rv = 0;
|
|
uint16_t endaddr;
|
|
|
|
if (eeaddr + len <= (eeaddr | (PAGE_SIZE - 1)))
|
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endaddr = eeaddr + len;
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else
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endaddr = (eeaddr | (PAGE_SIZE - 1)) + 1;
|
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len = endaddr - eeaddr;
|
|
|
|
#ifndef WORD_ADDRESS_16BIT
|
|
/* patch high bits of EEPROM address into SLA */
|
|
sla = TWI_SLA_24CXX | (((eeaddr >> 8) & 0x07) << 1);
|
|
#else
|
|
/* 16-bit address devices need only TWI Device Address */
|
|
sla = TWI_SLA_24CXX;
|
|
#endif
|
|
|
|
restart:
|
|
if (n++ >= MAX_ITER)
|
|
return -1;
|
|
begin:
|
|
|
|
/* Note [15] */
|
|
TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN); /* send start condition */
|
|
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
|
|
switch ((twst = TW_STATUS))
|
|
{
|
|
case TW_REP_START: /* OK, but should not happen */
|
|
case TW_START:
|
|
break;
|
|
|
|
case TW_MT_ARB_LOST:
|
|
goto begin;
|
|
|
|
default:
|
|
return -1; /* error: not in start condition */
|
|
/* NB: do /not/ send stop condition */
|
|
}
|
|
|
|
/* send SLA+W */
|
|
TWDR = sla | TW_WRITE;
|
|
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
|
|
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
|
|
switch ((twst = TW_STATUS))
|
|
{
|
|
case TW_MT_SLA_ACK:
|
|
break;
|
|
|
|
case TW_MT_SLA_NACK: /* nack during select: device busy writing */
|
|
goto restart;
|
|
|
|
case TW_MT_ARB_LOST: /* re-arbitrate */
|
|
goto begin;
|
|
|
|
default:
|
|
goto error; /* must send stop condition */
|
|
}
|
|
|
|
#ifdef WORD_ADDRESS_16BIT
|
|
TWDR = (eeaddr>>8); /* 16 bit word address device, send high 8 bits of addr */
|
|
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
|
|
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
|
|
switch ((twst = TW_STATUS))
|
|
{
|
|
case TW_MT_DATA_ACK:
|
|
break;
|
|
|
|
case TW_MT_DATA_NACK:
|
|
goto quit;
|
|
|
|
case TW_MT_ARB_LOST:
|
|
goto begin;
|
|
|
|
default:
|
|
goto error; /* must send stop condition */
|
|
}
|
|
#endif
|
|
|
|
TWDR = eeaddr; /* low 8 bits of addr */
|
|
TWCR = _BV(TWINT) | _BV(TWEN); /* clear interrupt to start transmission */
|
|
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
|
|
switch ((twst = TW_STATUS))
|
|
{
|
|
case TW_MT_DATA_ACK:
|
|
break;
|
|
|
|
case TW_MT_DATA_NACK:
|
|
goto quit;
|
|
|
|
case TW_MT_ARB_LOST:
|
|
goto begin;
|
|
|
|
default:
|
|
goto error; /* must send stop condition */
|
|
}
|
|
|
|
for (; len > 0; len--)
|
|
{
|
|
TWDR = *buf++;
|
|
TWCR = _BV(TWINT) | _BV(TWEN); /* start transmission */
|
|
while ((TWCR & _BV(TWINT)) == 0) ; /* wait for transmission */
|
|
switch ((twst = TW_STATUS))
|
|
{
|
|
case TW_MT_DATA_NACK:
|
|
goto error; /* device write protected -- Note [16] */
|
|
|
|
case TW_MT_DATA_ACK:
|
|
rv++;
|
|
break;
|
|
|
|
default:
|
|
goto error;
|
|
}
|
|
}
|
|
quit:
|
|
TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); /* send stop condition */
|
|
|
|
return rv;
|
|
|
|
error:
|
|
rv = -1;
|
|
goto quit;
|
|
}
|
|
|
|
/*
|
|
* Wrapper around ee24xx_write_page() that repeats calling this
|
|
* function until either an error has been returned, or all bytes
|
|
* have been written.
|
|
*/
|
|
int
|
|
ee24xx_write_bytes(uint16_t eeaddr, int len, uint8_t *buf)
|
|
{
|
|
int rv, total;
|
|
|
|
total = 0;
|
|
do
|
|
{
|
|
#if DEBUG
|
|
printf("Calling ee24xx_write_page(%d, %d, %p)",
|
|
eeaddr, len, buf);
|
|
#endif
|
|
rv = ee24xx_write_page(eeaddr, len, buf);
|
|
#if DEBUG
|
|
printf(" => %d\n", rv);
|
|
#endif
|
|
if (rv == -1)
|
|
return -1;
|
|
eeaddr += rv;
|
|
len -= rv;
|
|
buf += rv;
|
|
total += rv;
|
|
}
|
|
while (len > 0);
|
|
|
|
return total;
|
|
}
|
|
|
|
void
|
|
error(void)
|
|
{
|
|
|
|
printf("error: TWI status %#x\n", twst);
|
|
exit(0);
|
|
}
|
|
|
|
FILE mystdout = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);
|
|
|
|
void
|
|
main(void)
|
|
{
|
|
uint16_t a;
|
|
int rv;
|
|
uint8_t b[16];
|
|
uint8_t x;
|
|
|
|
ioinit();
|
|
|
|
stdout = &mystdout;
|
|
|
|
for (a = 0; a < 256;)
|
|
{
|
|
printf("%#04x: ", a);
|
|
rv = ee24xx_read_bytes(a, 16, b);
|
|
if (rv <= 0)
|
|
error();
|
|
if (rv < 16)
|
|
printf("warning: short read %d\n", rv);
|
|
a += rv;
|
|
for (x = 0; x < rv; x++)
|
|
printf("%02x ", b[x]);
|
|
putchar('\n');
|
|
}
|
|
#define EE_WRITE(addr, str) ee24xx_write_bytes(addr, sizeof(str)-1, str)
|
|
rv = EE_WRITE(55, "The quick brown fox jumps over the lazy dog.");
|
|
if (rv < 0)
|
|
error();
|
|
printf("Wrote %d bytes.\n", rv);
|
|
for (a = 0; a < 256;)
|
|
{
|
|
printf("%#04x: ", a);
|
|
rv = ee24xx_read_bytes(a, 16, b);
|
|
if (rv <= 0)
|
|
error();
|
|
if (rv < 16)
|
|
printf("warning: short read %d\n", rv);
|
|
a += rv;
|
|
for (x = 0; x < rv; x++)
|
|
printf("%02x ", b[x]);
|
|
putchar('\n');
|
|
}
|
|
|
|
printf("done.\n");
|
|
|
|
}
|