decided as my code was growing to split the source up into modules... and added a few tweaks along the way, i think that was my downfall, i should have just split it and re-tested it before doing the tweaks.
my i2c bit banger is ugly as heck, it was nice and readable full of calls but was incredibly slow so i replaced most of the calls with macros. and then decided to use af' instead of a memory byte to store the current bus state, but decided that was too slow still so unrolled the macros too
when i am sending a byte it's pretty much as fast as it'll go, the DS1307 is only rated at 100Khz speed and my clock pusle is 18t-states, 100khz been 16.5t-states per half cycles. of course it takes much longer to prepare the next bit of data around 60 t-states but at around 80t-states per bit thats getting on for a therectical speed of 5KBs
Code: Select all
;DO_TX
;
;SEND A BYTE TO I2C BUS
;
;ON ENTRY A=BYTE TO SEND
;
;USES BC,A
;
DO_TX:
LD B,8 ;COUNTER FOR 8 BITS
LD C,A ;BYTE TO SEND IN C
NEXT_TX_BIT:
SLA C ;SHIFT BIT OT SEND INTO CF
JR C,TX_BIT_HIGH
TX_BIT_LOW:
EX AF,AF'
AND %11101111
OUT (PORT08),A ;SDA LOW
EX AF,AF'
JR TX_DATA_SET
TX_BIT_HIGH:
EX AF,AF'
OR %00010000
OUT (PORT08),A ;SDA HIGH
EX AF,AF'
TX_DATA_SET:
EX AF,AF' ;USE ALTERNATIVE ACCUMULATOR
OR %00001000
OUT (PORT08),A ;SCL HIGH
;with macros there would have been an extra EX AF,AF'\ EX AF,AF' here....
AND %11110111
OUT (PORT08),A ;SCL LOW
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
DJNZ NEXT_TX_BIT ;MORE BITS ?
TX_ACK:
;TX_ACK IS A REALLY BAD NAME FOR THIS SECTION...
;DATA LINE IS FREE'D AND THE ACK BIT IF ANY
;IS RECIEVED FROM THE SLAVE DEVICE
;BUT IS CLOCKED FROM THE MASTER
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
OR %00010000
OUT (PORT08),A ;FREE SDA (HIGH)
;with macros there would have been an extra EX AF,AF'\ EX AF,AF' here....
OR %00001000
OUT (PORT08),A ;SCL HIGH
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
IN A,(PORT08) ;READ THE SDA LINE.
;DO NOTHING WITH IT !
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
AND %11110111
OUT (PORT08),A ;SCL LOW
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
RET
Code: Select all
;DO_RX
;
;RECIEVE A BYTE FROM I2C BUS
;
;ON ENTRY IF A<>0 ACK WILL BE SENT
;ELSE NO ACK
;
;BYTE RETURNED IN A
;
;USES BC, A
;
DO_RX:
PUSH AF ;SAVE AF (A NONZERO will send ACK bit)
LD B,8 ;COUNTER FOR 8 BITS
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
OR %00010000
OUT (PORT08),A ;SDA FREE (HIGH)
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
NEXT_RX_BIT:
SLA C ;SHIFT A ZERO INTO BIT 0
;WILL BE ALTERED LATER IF RECIEVED
;BIT IS 1
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
OR %00001000
OUT (PORT08),A ;SCL HIGH
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
;I MIGHT TRY IT WITHOUT THIS WAITING TO SEE IF THE SLAVE DEVICE
;IS CLOCK STRECTING AND SEE IF IT STILL WORKS OK
CLK_STRETCH:
IN A,(PORT08) ;WAIT FOR THE OTHER
AND SCL_IN ;DEVICE WHICH MAY
JR Z,CLK_STRETCH ;BE CLOCK STRECTHING
READ_BIT:
IN A,(PORT08)
AND SDA_IN ;ONLY TEST THE DATA BIT
JR Z,BIT_DONE
BIT_ONE:
SET 0,C ;RX BIT WAS ONE; BIT 0 OF C ALREADY CONTAINS 0
BIT_DONE:
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
AND %11110111
OUT (PORT08),A ;SCL LOW
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
DJNZ NEXT_RX_BIT
BYTE_DONE: ;SEND AN ACK BIT ?
;NO ACK TELLS SLAVE DEVICE THAT WAS THE
;LAST BYTE TO SEND
POP AF
AND A ;REMEBER NON ZERO = DO ACK
JR Z,NO_ACK
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
AND %11101111
OUT (PORT08),A ;SDA LOW (ACK BIT)
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
JR DO_9TH ;JUMP TO 9TH CLOCK PULSE
NO_ACK:
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
OR %00010000
OUT (PORT08),A ;SDA HIGH (IT'S PROBABLY ALREADY HIGH.)
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
DO_9TH:
EX AF,AF' ;USE ALTERNATE ACCUMULATOR
OR %00001000
OUT (PORT08),A ;SCL HIGH
AND %11110111
OUT (PORT08),A ;SCL LOW
OR %00010000
OUT (PORT08),A ;SDA HIGH
EX AF,AF' ;BACK TO NORMAL ACCUMULATOR
LD A,C ;RECIEVED BYTE IN A
RET
then i could get creative and have the seconds fill up on even minutes and thne un-fill on the next, maybe some kind of binary mode might be fun... lots of ideas now i'm thinking about it.i hope to get some video on youtube over the weekend
Regards Andy
