Trying to learn more about I2C communication. An EEPROM chip is a great way to learn as it supports both read and write functions. The SMBus App Note for the C8051F410 was overly complex to implement so I worked out a bit bang protocol in assembly. The App Note details working with a small EEPROM from Microchip – 24LC02B:
A link to the datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/24AA02-24LC02B-24FC02-Data-Sheet-20001709L.pdf
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| ; simple I2C protocol for C8051F410 with EEPROM 24LC02B-I/P-ND from Microchip | |
| ; I used LAoE bitflip.a51 as a starting point from | |
| ; https://learningtheartofelectronics.com/program-listings/silabs-code/lab-c1/ | |
| ; demonstrates simple read and write | |
| $NOSYMBOLS ; keeps listing short.. | |
| $INCLUDE (C:\MICRO\8051\RAISON\INC\c8051f410.inc) | |
| SCL EQU P0.0 ; clock | |
| SDA EQU P0.1 ; data | |
| BLUE_LED EQU P0.4 ; an LED is always nice | |
| ORG 0 ; tells assembler the address at which to place this code | |
| SJMP STARTUP ; here code begins--with just a jump to start of | |
| ; real program. ALL our programs will start thus | |
| ORG 80h ; ...and here the program starts | |
| STARTUP: | |
| ACALL USUAL_SETUP | |
| ACALL IO_SETUP | |
| SETB BLUE_LED | |
| SETB SCL ; initialize with SCL, SDA high | |
| SETB SDA | |
| MAIN: CPL BLUE_LED ; flips LED | |
| MOV R1, #0E1h ; R1 holds value | |
| MOV R2, #00h ; R2 holds the address | |
| ACALL EEPROM_WRITE ; Call the write function | |
| ACALL DELAY ; Need sufficient delay between write cycles! | |
| ACALL DELAY ; Polling would be more efficient | |
| ACALL DELAY ; See data sheet for example! | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| MOV R1, #23h | |
| MOV R2, #01h | |
| ACALL EEPROM_WRITE | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| ACALL DELAY | |
| MOV R2, #00h ; R2 holds address | |
| ACALL EEPROM_READ ; Read this address | |
| MOV R7, ACC ; When return, accumultor holds read value | |
| MOV R2, #01h | |
| ACALL EEPROM_READ | |
| MOV R6, ACC | |
| STUCK: | |
| SJMP STUCK ; Stop here - good idea not to repeat writes to wear out EEPROM! | |
| ; EEPROM WRITE AND READ FUNCTIONS | |
| EEPROM_WRITE: | |
| ACALL I2C_START | |
| MOV A, #0A0h | |
| ACALL I2C_SEND_BYTE | |
| MOV A, R2 | |
| ACALL I2C_SEND_BYTE | |
| MOV A, R1 | |
| ACALL I2C_SEND_BYTE | |
| LCALL I2C_STOP | |
| LCALL DELAY | |
| RET | |
| EEPROM_READ: | |
| ACALL I2C_START ; START I2C | |
| MOV A, #0A0h ; SEND WRITE COMMAND | |
| ACALL I2C_SEND_BYTE | |
| MOV A, R2 ; WRITE THE ADDRESS TO THE ADDRESS REG. | |
| ACALL I2C_SEND_BYTE | |
| SETB SCL ; NEED TO SEND ANOTHER START FOR THE SLAVE so reinitialize with SCL, SDA high | |
| SETB SDA | |
| ACALL I2C_START ; 2nd start | |
| MOV A, #0A1h; This is READ | |
| ACALL I2C_SEND_BYTE ; Sends READ command | |
| ACALL I2C_READ_BYTE ; Reads the byte | |
| LCALL I2C_STOP ; STOP | |
| LCALL DELAY | |
| RET | |
| I2C_START: ; start condition | |
| CLR SDA | |
| CLR SCL | |
| RET | |
| I2C_STOP: ; stop condition | |
| CLR SDA | |
| CLR SCL | |
| SETB SCL | |
| SETB SDA | |
| RET | |
| ;Send Byte assumess accumulator loaded with byte you want to send. | |
| ;Basically, just reads bit 7 and pulses SDA appropriately, along with a clock pulse. | |
| ;Then, all bits are shifted and the process is repeated until all 8 bits are sent. | |
| ;After the 8 bits, an acknowledgement bit is sent. | |
| I2C_SEND_BYTE: | |
| MOV R0, #08 | |
| I2C_SEND_LOOP: | |
| JB ACC.7, GO_HIGH | |
| GO_LOW: | |
| ACALL I2C_LOW | |
| SJMP CONTINUE | |
| GO_HIGH: | |
| ACALL I2C_HIGH | |
| SJMP CONTINUE | |
| CONTINUE: | |
| RL A | |
| DJNZ R0, I2C_SEND_LOOP | |
| I2C_SEND_BYTE_DONE: | |
| ACALL I2C_HIGH //ACK | |
| RET | |
| I2C_HIGH: | |
| SETB SDA ; data high | |
| SETB SCL ; Clock hi edge | |
| SETB SDA ;stay high | |
| CLR SCL ; clear clock | |
| RET | |
| I2C_LOW: | |
| CLR SDA ; data low | |
| SETB SCL ; clock edge hi | |
| CLR SDA ; stay low | |
| CLR SCL ; clear clock | |
| RET | |
| ; I2C READ BYTE | |
| ; Assumes slave is ready to send data. | |
| ; Basically, sends clock pulses and polls SDA and sets/clears ACC.0 depending on value. | |
| ; Then, the ACC is left shifted until the byte is read. | |
| ; Read byte is left in accumulator upon return from subroutine | |
| I2C_READ_BYTE: | |
| MOV R0, #08 | |
| MOV ACC, #00h | |
| I2C_READ_LOOP: | |
| RL A | |
| SETB SCL; clock edge hi | |
| JB SDA, READ_HIGH | |
| READ_LOW: | |
| CLR ACC.0 | |
| SJMP CONTINUE_READ | |
| READ_HIGH: | |
| SETB ACC.0 | |
| SJMP CONTINUE_READ | |
| CONTINUE_READ: | |
| CLR SCL; clock low | |
| DJNZ R0, I2C_READ_LOOP | |
| I2C_SEND_BYTE_DONE_READ: | |
| ACALL I2C_HIGH //ACK | |
| RET | |
| DELAY: | |
| MOV R0, #20h | |
| WAIT: | |
| DJNZ R0, WAIT | |
| RET | |
| USUAL_SETUP: ; Disable the WDT. | |
| anl PCA0MD, #NOT(040h) ; Clear Watchdog Enable bit | |
| ; Enable the Port I/O Crossbar | |
| mov XBR1, #40h ; Enable Crossbar | |
| ret | |
| IO_SETUP: orl P0MDOUT, #01h ; enable P0.0 as push-pull output | |
| RET | |
| END | |
