benag6
Newbie level 4
ade77xx
Hi friends,
I have two doubts regarding
1.interfacing external eeprom interfacing.
If ext.eeprom (for eg AT24c04) is directly connected to atmega16 with correct 10k pull up resistor, I am not getting the proper channel set for data flow and hence data transfer doesn't takes place but when i changed volatge from Vcc(5v) to 3.3v it worked.why?
2. I have the below subroutine to know the spi working.
Below is a subroutine part of 4-wire interface:
It is not working. Can anyone find any faults in it. I also like to know about any precise volatge values has to be given at din and dout pin.
suggest me ideas, view.
nakkeeran
//program to know the working of data transfer using SPI.
.include "m16def.inc"
.def temp = r16
.def temp1 = r17
.def data = r19
.equ sclk = 7 ;PB7 pin
.equ cs = 4 ;PB4 pin
.equ mosi = 5 ;PB5 pin
.equ miso = 6 ;PB6 pin
.cseg
.org $0
jmp reset
reti
reset:
ldi temp1,low(ramend)
out spl,temp1 ;set lowbyte for sp
ldi temp1,high(ramend)
out sph,temp1 ;set highbyte for sp
ldi temp,0xff;
out DDRC,temp
out DDRA,temp
out DDRD,temp
checkingSPI:
init_spi:
ldi temp,0xb0;direction settings in portB.
out DDRB,temp;
ldi temp,0x70;initial port pulses as high
out portb,temp;
ldi temp,$55;control reg is set for falling edges. hence cpha=1.
out spcr,temp
writecmd_spi:
ldi data,$8a;this is the address where data has to be stored,also bit 7 is for write enable.
cbi portb,4;cs=low
out spdr,data
intrpflag:
sbis spsr,spif
rjmp intrpflag
call w_16ms
writedata_spi:
cbi PORTB,4
ldi data,$33 ; this is data
out spdr,data
getintrpflag:
sbis spsr,spif
rjmp getintrpflag
sbi PORTB,4;//set bit chipselect
readcmd_spi:; this is the reading data routine.
ldi data,$0a;this is data reading address,here 0 at bit 7 is read enable.
cbi portb,4
out spdr,data
getintrflag:
sbis spsr,spif
rjmp getintrflag
call w_16ms
read_data_spi:
cbi PORTB,4
ldi data,$51;some rough value.
out spdr,data
getintr4:
sbis spsr,spif
rjmp getintr4
in data,spdr
out portd,data; displaying the data here it shd be $33.
rep:rjmp rep
Hi friends,
I have two doubts regarding
1.interfacing external eeprom interfacing.
If ext.eeprom (for eg AT24c04) is directly connected to atmega16 with correct 10k pull up resistor, I am not getting the proper channel set for data flow and hence data transfer doesn't takes place but when i changed volatge from Vcc(5v) to 3.3v it worked.why?
2. I have the below subroutine to know the spi working.
Below is a subroutine part of 4-wire interface:
It is not working. Can anyone find any faults in it. I also like to know about any precise volatge values has to be given at din and dout pin.
suggest me ideas, view.
nakkeeran
//program to know the working of data transfer using SPI.
.include "m16def.inc"
.def temp = r16
.def temp1 = r17
.def data = r19
.equ sclk = 7 ;PB7 pin
.equ cs = 4 ;PB4 pin
.equ mosi = 5 ;PB5 pin
.equ miso = 6 ;PB6 pin
.cseg
.org $0
jmp reset
reti
reset:
ldi temp1,low(ramend)
out spl,temp1 ;set lowbyte for sp
ldi temp1,high(ramend)
out sph,temp1 ;set highbyte for sp
ldi temp,0xff;
out DDRC,temp
out DDRA,temp
out DDRD,temp
checkingSPI:
init_spi:
ldi temp,0xb0;direction settings in portB.
out DDRB,temp;
ldi temp,0x70;initial port pulses as high
out portb,temp;
ldi temp,$55;control reg is set for falling edges. hence cpha=1.
out spcr,temp
writecmd_spi:
ldi data,$8a;this is the address where data has to be stored,also bit 7 is for write enable.
cbi portb,4;cs=low
out spdr,data
intrpflag:
sbis spsr,spif
rjmp intrpflag
call w_16ms
writedata_spi:
cbi PORTB,4
ldi data,$33 ; this is data
out spdr,data
getintrpflag:
sbis spsr,spif
rjmp getintrpflag
sbi PORTB,4;//set bit chipselect
readcmd_spi:; this is the reading data routine.
ldi data,$0a;this is data reading address,here 0 at bit 7 is read enable.
cbi portb,4
out spdr,data
getintrflag:
sbis spsr,spif
rjmp getintrflag
call w_16ms
read_data_spi:
cbi PORTB,4
ldi data,$51;some rough value.
out spdr,data
getintr4:
sbis spsr,spif
rjmp getintr4
in data,spdr
out portd,data; displaying the data here it shd be $33.
rep:rjmp rep