WebSVN – group.electronics – Blame – /PIC_Projects/PIC_Tutorial/Part01-I2C/master00.asm

Rev	Author	Line No.	Line
3	-	1	`list p=16F84A`
		2	`include "p16F84a.inc"`
		3
		4	`;***** CONFIGURATION`
		5	`__CONFIG _PWRTE_ON & _HS_OSC & _WDT_OFF`
		6
		7	`; pin assignments`
		8	`#define SDA 0 ; Pin 0`
		9	`#define SCL 1 ; Pin 1`
		10	`#define TRIS_SDA TRISB,SDA`
		11	`#define TRIS_SCL TRISB,SCL`
		12	`#define I2C_SDA PORTB,SDA`
		13	`#define I2C_SCL PORTB,SCL`
		14	`#define LED PORTB,2`
		15
		16	`#define I2C_SLAVE1 0x27`
		17
		18	`CBLOCK 0CH`
		19	`counter`
		20
		21	`_I`
		22	`byte_send`
		23	`i2c_addr`
		24
		25	`i2c_ret ; I2C Return Value`
		26
		27	`dly_loop1 ; Loops for delays`
		28	`dly_loop2`
		29	`ENDC`
		30
		31	`ORG 0`
		32	`goto start ; jump over to main routine`
		33
		34	`;***** Initialisation`
		35	`start`
		36	`; configure ports`
		37	`clrw ; configure PORTB and PORTC as all outputs`
		38	`tris PORTB`
		39	`clrf PORTB`
		40
		41	`movlw b'00000000' ; Init our counter`
		42	`movwf counter`
		43
		44	`;***** Main loop`
		45	`main_loop`
		46	`bsf LED`
		47	`call SendCount`
		48	`bcf LED`
		49
		50	`goto main_loop`
		51
		52	`SendCount`
		53
		54	`movlw I2C_SLAVE1 ; 7-bit address of dev`
		55	`bcf STATUS,C ; Use Write mode ('0')`
		56	`call I2C_Start ; Start a transmission`
		57	`call ReadAck ; Wait for Ack from slave`
		58	`movf i2c_ret ; Check return value`
		59	`btfss STATUS,Z ; Goto SendEnd on NACK`
		60	`goto SendErr`
		61
		62	`movfw counter ; Copy byte to write (counter) to w`
		63	`call I2C_Write ; Write the byte to the line`
		64	`call ReadAck ; Should read byte from bus here`
		65	`; checking that its a Nack`
		66
		67	`call I2C_End ; End the packet`
		68	`bcf LED`
		69	`incf counter,f`
		70	`call Delay_Short`
		71	`return`
		72
		73	`SendErr`
		74	`call I2C_End`
		75
		76	`;call Delay_Long ; Wait a while before resend`
		77	`return`
		78
		79	`I2C_Start`
		80	`movwf i2c_addr ; Save the address in W`
		81	`rlf i2c_addr,f ; Attach '0' to 8th bit`
		82	`call Start ; Start the Trans`
		83	`movfw i2c_addr`
		84	`call I2C_Write ; Write byte to port`
		85	`return`
		86
		87	`I2C_End`
		88	`call Stop`
		89	`return`
		90
		91	`I2C_Write`
		92	`movwf byte_send`
		93	`movlw .8 ; 8 bits to send`
		94	`movwf _I`
		95	`_WriteBit`
		96	`rlf byte_send,f ; Move highest bit to C`
		97	`btfss STATUS,C ; If 'C' is clear`
		98	`call SDA_Low ; -> Set data low`
		99	`btfsc STATUS,C ; If 'C' is set`
		100	`call SDA_High ; -> Set data high`
		101
		102	`call SCL_Pulse`
		103
		104	`decfsz _I,f ; Decrement counter, if not clear`
		105	`goto _WriteBit ; -> Send next bit`
		106	`call SDA_Low ; Set low to allow slave to write`
		107	`return`
		108
		109	`Nack ; Clock a high SDA`
		110	`call SDA_High`
		111	`call SCL_Pulse`
		112	`return`
		113
		114	`Ack ; Clock a high SDA`
		115	`call SDA_Low`
		116	`call SCL_Pulse`
		117	`return`
		118
		119	`ReadAck`
		120	`call SCL_High`
		121	`clrf i2c_ret`
		122	`btfsc I2C_SDA`
		123	`bsf i2c_ret,0`
		124	`call SCL_Low`
		125	`return`
		126
		127	`Start`
		128	`call SDA_High`
		129	`call SCL_High`
		130	`call SDA_Low`
		131	`call SCL_Low`
		132	`return`
		133
		134	`Stop ; Bring SDA high while Clock high`
		135	`call SCL_Low`
		136	`call SDA_Low`
		137	`call SCL_High`
		138	`call SDA_High`
		139	`return`
		140
		141	`SCL_Pulse`
		142	`call SCL_High`
		143	`call SCL_Low`
		144	`return`
		145
		146	`SDA_High`
		147	`bsf STATUS,RP0 ; Bank 1`
		148	`bsf TRIS_SDA ; Make SDA pin input`
		149	`bcf STATUS,RP0 ; Back to bank 0`
		150	`call Delay_Short`
		151	`return`
		152
		153	`SDA_Low`
		154	`bcf I2C_SDA`
		155	`bsf STATUS,RP0`
		156	`bcf TRIS_SDA ; Make SDA pin output`
		157	`bcf STATUS,RP0`
		158	`call Delay_Short`
		159	`return`
		160
		161	`SCL_High`
		162	`bsf STATUS,RP0 ; Bank 1`
		163	`bsf TRIS_SCL ; Make SDA pin input`
		164	`bcf STATUS,RP0 ; Back to bank 0`
		165	`call Delay_Short`
		166	`return`
		167
		168	`SCL_Low`
		169	`bcf I2C_SCL`
		170	`bsf STATUS,RP0`
		171	`bcf TRIS_SCL ; Make SDA pin output`
		172	`bcf STATUS,RP0`
		173	`call Delay_Short`
		174	`return`
		175
		176	`Delay_Short ; 25us delay`
		177	`movlw .5`
		178	`movwf dly_loop2`
		179	`Delay_Short_1`
		180	`nop`
		181	`decfsz dly_loop2,f`
		182	`goto Delay_Short_1`
		183	`return`
		184
		185	`Delay_Long`
		186	`movlw .250 ; 250ms delay`
		187	`movwf dly_loop1`
		188	`Outer`
		189	`movlw .110 ; Close to 1ms when set to .110`
		190	`movwf dly_loop2`
		191	`Inner`
		192	`nop`
		193	`nop`
		194	`nop`
		195	`nop`
		196	`nop`
		197	`nop`
		198	`decfsz dly_loop2,f`
		199	`goto Inner`
		200	`decfsz dly_loop1,f`
		201	`goto Outer`
		202	`return`
		203
		204	`END`

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