Multi-slave SPI using ATmega32s

[Charisma]

Hello everyone!
I'm trying to do a project in which I have to get two temperatures from two different locations using LM35s, do the appropriate signal conditioning with 2 Slave AT32s and then send the data to a 3rd AT32 ( the Master). The master has to take the average temperature and send it to a LCD.
here's my schematic and then follows my code:

Slave First (who said Masters come first?):

        .INCLUDE"M32DEF.INC"
	.EQU SS=4

	LDI R16,HIGH(RAMEND)	;STACK SETTINGS
	OUT SPH,R16
	LDI R16,LOW(RAMEND)
	OUT SPL,R16
;=================IO SETTINGS=================
	CBI DDRB,7
	SBI DDRB,6
	CBI DDRB,5
	CBI DDRB,4

	CBI DDRA,0
	
;=================SPI SETTINGS=====================
	LDI R16,(1<< SPE) 
	OUT SPCR,R16
;==================ADC SETTINGS====================
	LDI R16,( 1<<REFS1 | 1<<REFS0 | 1<<ADLAR )
	OUT ADMUX,R16

	LDI R16,( 1<<ADEN | 1<< ADPS2 | 1<<ADPS1 |1 << ADPS0 )
	OUT ADCSRA,R16
;==================================================

READ_TEMP:
	SBI ADCSRA,ADSC
WAIT_ADC:
	SBIS ADCSRA,ADIF
	RJMP WAIT_ADC
	SBI ADCSRA,ADIF
	IN R16,ADCH
WAIT_SPI:
	SBIS PINB,SS
	SBIS SPSR,SPIF
	RJMP WAIT_SPI
	IN R0,SPDR
	OUT SPDR,R16
	RJMP READ_TEMP

Master:

	.INCLUDE"M32DEF.INC"

	.EQU SS1 = 0
	.EQU SS2 = 1
	.EQU RS = 1
	.EQU EN = 0
	.EQU LCD_PORT = PORTD


	LDI R16,HIGH(RAMEND)	;STACK SETTINGS
	OUT SPH,R16
	LDI R16,LOW(RAMEND)
	OUT SPL,R16
;=================IO SETTINGS=================
	LDI R16,0xFF	;LCD
	OUT DDRD,R16
	SBI DDRC,0	
	SBI DDRC,1

	SBI DDRB,7		;SPI
	CBI DDRB,6
	SBI DDRB,5

	SBI DDRA,0		;SLAVE SELECT
	SBI DDRA,1
;=================SPI SETTINGS=====================
	SBI PORTA,SS1		;SLAVES OFF
	SBI PORTA,SS2
	
	LDI R16,(1<< SPE | 1<< MSTR ) 
	OUT SPCR,R16

;================LCD SETTINGS=================

	CBI PORTC,EN
	CALL DELAY2MS
	LDI R16,0x38
	CALL CW
	CALL DELAY2MS
	LDI R16,0x0E
	CALL CW
	LDI R16,0x01
	CALL CW
	CALL DELAY2MS

	CALL DELAY2MS
	CALL DELAY2MS
TRANSMIT:
	CBI PORTA,SS1 ;ENABLE SLAVE1
	LDI R16,0xFF
	OUT SPDR,R16 ;START THE TRANSMITION
WAIT1:
	SBIS SPSR,SPIF ;CHECK FOR TRANSMITION COMPLETION.
	RJMP WAIT1
	IN R20,SPDR
	SBI PORTA,SS1 ;DISABLE SLAVE1

	CBI PORTA,SS2 ;ENABLE SLAVE2
	LDI R16,0xFF
	OUT SPDR,R16 ;START THE TRANSMITION
WAIT2:
	SBIS SPSR,SPIF ;CHECK FOR TRANSMITION COMPLETION.
	RJMP WAIT2
	IN R21,SPDR
	SBI PORTA,SS2 ;DISABLE SLAVE2
	
	ADD R21,R20
	LSR R21
	CALL DISP
	RJMP TRANSMIT
	
;===============SUB-ROUTINES==================================
CW:
	OUT LCD_PORT,R16
	CBI PORTC,RS
	SBI PORTC,EN
	CALL SDELAY
	CBI PORTC,EN
	CALL DELAY100US
	RET
DW:
	OUT LCD_PORT,R16
	SBI PORTC,RS
	SBI PORTC,EN
	CALL SDELAY
	CBI PORTC,EN
	CALL DELAY100US
	RET

SDELAY:
	NOP
	NOP
	RET

DELAY100US:
	PUSH R17
	LDI R17,60
L1: CALL SDELAY
	DEC R17
	BRNE L1
	POP R17
	RET

DELAY2MS:
	PUSH R17
	LDI R17,20
L2:	CALL DELAY100US
	DEC R17
	BRNE L2
	POP R17
	RET

DISP:;==============EXTRACT DIGIGTS , CONVERT TO ASCII AND DISPLAY================
	CLR R11
	MOV R24,R21
DL1:CPI R24,10
	BRLO NEXT
	SUBI R24,10
	INC R25
	RJMP DL1
NEXT:
	LDI R16,48
	ADD R24,R16
	ADD R25,R16
	
	LDI R16,0x01
	CALL CW	
	LDI R16,'T'
	CALL DW
	LDI R16,'E'
	CALL DW
	LDI R16,'M'
	CALL DW
	LDI R16,'P'
	CALL DW
	LDI R16,':'
	
	MOV R16,R11
	CALL DW
	MOV R16,R10
	CALL DW

	RET

My problem is that I can't seem to get the SPI running. I get DATA OVERRUN and COLLISION errors every time. Could you give me a hand?

 

[embpic]

there is problen in hardware as you shown.
there is problen in MISO and slave select pin.
which IC is master U3,U2 or U5.

 

[Charisma]

Sorry, Originally the schematic was right, I made a change that messed it up. Anyway , I fixed the schematic and the errors persist. I fixed the schematic in the original post.Master is U5 , the other two are slaves.

 

[Venkadesh_M]

A data collision will occur if you put the second data before the first byte transmit completes..
Or a new data arrives in the receive buffer before you read the last byte That may be some times called as a over run..

so wait after the first transmit and put the second data..

 

[Charisma]

thanks , I knew that but that's percisely the reason for

SBIS SPSR,SPIF ;CHECK FOR TRANSMISSION COMPLETION.
	RJMP WAIT2

yet it doesn't work. could you please take a look at the code, spi section.
thanks in advance

 

[Venkadesh_M]

The problem is I not coding in assembly............