an_008.asm

One of the most important issues affecting the implementation of microcontroller software deals wi

;*****************************************************************************
;	APPLICATION NOTE AN008 
;	Oversampling and data decision for the CC400/CC900
;
;	File : 		AN_008.asm
;
;	Microcontroller:
;			Microchip PIC16F87x or compatible
;			Can be adapted to all mid-range
;			PIC controllers with enough program
;			memory by changing I/O definitions
;
;	Author :	Code originally written by Kjell Tore Heien
;			Modified by Karl H. Torvmark
;
;	Contact :	Chipcon AS [phone]
;			[e-mail]
;
;	Version :	1.2 - 2001-08-14
;
;*****************************************************************************

;*****************************************************************************
;	DESCRIPTION
;  General:
;	This code oversamples the output signal from a
;	CC400/CC900 RF-transceiver. The output signal is coded
;	in Manchester format, the MCU converts to NRZ format by
;	taking 8 samples/bit. Signal decision is based on the 
;	majority of these samples, so noise will be filtered out.
;	
;	The MCU can also be used to transmision. The MCU reads NRZ
;	signals, sending it to the transceiver in Manchester format.
;	
;	The configuration of CCX00 is done by the MCU, with three
;	possible modes, Transceive(TX), Receive (RX) and Power Down (PD)
;	In PowerDown mode, both the transceiver and MCU are powered
;	down (sleep)
;	
;	The code needs to be changed to fit the application. The values
;	for the configuration registers in CCX00 must be calculated in
;	SmartRF Studio for the actual parameters and copied into the code.
;	(A_RX_H_val to H_PD_L_val)
;	
;	Also some timing variables must be changed to match the data 
;	rate (TIMING_RX, TIMING_TX, Rate_RX and Rate_TX).
;	See application note for formulas and values.
;	
;  Resources:
;	Program memory	:	428 words
;	I/O pins	:	Port B pins 0,1,2,4 and 5
;				Port C pins 0,1,2,3 and 4
;	Peripherals	:	TMR0
;
;
;  Mode configuration:
;
;	*********************************************************
;	* PIN	      		*	     MODE		*
;	*************************				*
;	* PD *  RX_TX 		*				*
;	*********************************************************
;	* 0  *  0     		*	Transmit mode (TX)	*
;	* 0  *  1     		* 	Receive mode (RX)	*
;	* 1  *  X (Don't care)	*	Power-down mode (PD)	*
;	*********************************************************
;
;  Timing in TX mode:
;			   	  _   _   _   _   _   _   _   _   _
;	CLK_OUT		 	_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/	 
;
;	DATA_IN pin (NRZ)	 | b1| b2| b3| b4| b5| b6| b7| b8| b9|    
;	DATA_IN pin read	R   R   R   R   R   R   R   R   R   R
;				 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
;	DIO pin (Manchester)	|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_| 
;
;  Timing in RX mode:
;				 _______ _______ _______ _______ _____
;	DIO pin (Manchester)	|_______|_______|_______|_______|_____
;	Sample			 S S S S S S S S S S S S S S S S S S S
;				         _______         _______
;	CLOCK_OUT pin		________/       \_______/       \_____
;				 _______________ _______________ _____
;	DATA_OUT pin		|_______________|_______________|_____
;				
;				|     Bit 1     |     Bit 2     |  Bit 3 ...
;
;	
;*****************************************************************************


;*****************************************************************************
; This part gives names to predefined MCU registers
; Overview of ports:
; 
; 	PORT:		PORTB 		- User interface
;	pin 0		CLK_OUT		- Clock out
;	pin 1		DATA_IN		- Data in (TX mode)
;	pin 2		DATA_OUT	- Data out (RX mode)
;	pin 3		unused		-
;	pin 4		PD		- System configuration (PD(1))
;	pin 5		RX_TX		- System configuration (RX(1)/TX(0))
;	pin 6		unused		-
;	pin 7		unused		-
;
;	PORT:		PORTC		- Communication with CC700/CC900
;	pin 0		PDATA		- Configuration pin
;	pin 1		CLOCK		- Configuration pin
;	pin 2		STROBE		- Configuration pin
;	pin 3		DIO		- Bi-directional data pin
;	pin 4		SYNC		- Synchronisation status
;	pin 5		unused		-
;	pin 6		unused		-
;	pin 7		unused		-
;*****************************************************************************

#define OPTION_REG      0x01
#define TMR0            0x01
#define PCL            	0x02
#define STATUS          0x03
#define CARRY           0
#define Z               2
#define RP0             5
#define RP1             6
#define PORTB           0x06
#define CLK_OUT         0
#define DATA_IN         1
#define DATA_OUT        2
#define PD              4
#define RX_TX           5
#define PORTC           0x07
#define PDATA           0
#define CLOCK           1
#define STROBE          2
#define DIO             3
#define TRISB           0x06
#define TRISC           0x07
#define INTCON          0x0B
#define RBIF            0
#define INTF            1
#define T0IF            2
#define RBIE            3
#define T0IE            5
#define GIE             7


;*****************************************************************************
; This part gives names to variables and status registers
; mapped in the general purpose registers
;*****************************************************************************

#define X               0x20        
#define A               0x22
#define An1             0x23
#define An2             0x24
#define A_LIMIT         0x25
#define A_LIMIT2    	0x2F
#define R               0x26
#define COUNT           0x27
#define COUNT_LIMIT     0x28    
#define CONTROL         0x29      
#define R_ENABLE        0       
#define SYNC            1
#define CONF_LOOP       2       
#define TEMP            0x2A
#define TEMP1           0x2B
#define TEMP2           0x2C
#define INPUT           0x2D
#define DI              0
#define MODE            0x2E
#define RXTX            0
#define NUMBER          1
#define READ            2
#define CONFIG_REG 	0x40        
#define TABLE_PT 	0x41
#define REG_COUNTER 	0x42
#define BIT_COUNTER 	0x43
#define BIT_ERRORS	0x44

;*****************************************************************************
; Status flags in registers are defined as follows :
;
; CONTROL (address 0x29)
; Bit number	Flag
;    	0	R_ENABLE
;	1	SYNC
;	2	CONF_LOOP
;	3	unused
;	4	unused
;	5	unused
;	6	unused
;	7	unused
;
; INPUT (address 0x2D)
; Bit number	Flag
;	0	DI
;	1	unused
;	2	unused
;	3	unused
;	4	unused
;	5	unused
;	6	unused
;	7	unused
;
; MODE (address 0x2E)
; Bit number	Flag
;	0	RXTX
;	1	NUMBER
;	2	READ
;	3	unused
;	4	unused
;	5	unused
;	6	unused
;	7	unused
;
;*****************************************************************************	

       
;*****************************************************************************
; Configurations value for CC700/CC900, given by SmartRF Studio
; These values must be changed to match the application.
; The 3 most significant bits of A_RX_H_val contain the address of register A
; in the CC700/CC900. The rest of A_RX_H_val contains the 5 bits in
; register A for RX mode. A_RX_L_val contains the 8 least significant bits of
; register A (Similar for register B-H).
;*****************************************************************************

;*****************************************************************************
; Default values:
;
;	Chip used	:	CC400
;
;	X-tal frequency	:	12.000000 MHz
;	X-tal accuracy	:	50 ppm
;	RF frequency	:	433.920000
;	IF Stage	:	200 kHz
;	Frequency sep.	:	10 kHz
;	Data rate	:	1.2 kbit/s
;	Power amp. class:	Class B
;	RF output power	:	10 dBm
;	Receiver mode	:	Optimum sensitivity
;	LOCK indicator	:	Continous
;	VCO current	:	000 (Maximum)
;*****************************************************************************


A_RX_H_val      EQU     0x00              
A_RX_L_val      EQU     0x2A
B_RX_H_val      EQU     0x23
B_RX_L_val      EQU     0x0B
C_RX_H_val      EQU     0x41
C_RX_L_val      EQU     0x41
D_RX_H_val      EQU     0x67
D_RX_L_val      EQU     0x71
E_RX_H_val      EQU     0x8A
E_RX_L_val      EQU     0x00
F_RX_H_val      EQU     0xB8
F_RX_L_val      EQU     0x03
G_RX_H_val      EQU     0xD2
G_RX_L_val      EQU     0x4C
H_RX_H_val      EQU     0xE4
H_RX_L_val      EQU     0x50

A_TX_H_val      EQU     0x08         
A_TX_L_val      EQU     0x2A
B_TX_H_val      EQU     0x23
B_TX_L_val      EQU     0x0B
C_TX_H_val      EQU     0x41
C_TX_L_val      EQU     0x41
D_TX_H_val      EQU     0x67
D_TX_L_val      EQU     0xA4
E_TX_H_val      EQU     0x8A
E_TX_L_val      EQU     0x14
F_TX_H_val      EQU     0xB8
F_TX_L_val      EQU     0x03
G_TX_H_val      EQU     0xD2
G_TX_L_val      EQU     0x4C
H_TX_H_val      EQU     0xE8
H_TX_L_val      EQU     0x60

A_PD_H_val      EQU     0x18         
A_PD_L_val      EQU     0x2A
B_PD_H_val      EQU     0x23
B_PD_L_val      EQU     0x0B
C_PD_H_val      EQU     0x41
C_PD_L_val      EQU     0x51
D_PD_H_val      EQU     0x67
D_PD_L_val      EQU     0x71
E_PD_H_val      EQU     0x8A
E_PD_L_val      EQU     0x00
F_PD_H_val      EQU     0xB8
F_PD_L_val      EQU     0x03
G_PD_H_val      EQU     0xD2
G_PD_L_val      EQU     0x4C
H_PD_H_val      EQU     0xE8
H_PD_L_val      EQU     0x60


;*****************************************************************************
; These constants must not be changed
;*****************************************************************************

TABLE_PT_val 		EQU     0x00
SAMPLE_HALF		EQU	0x03
SAMPLE_ALL		EQU	0x07


;*****************************************************************************
; These values must be changed when using different combinations of bit-rates
; and MCU clock frequencies. Sets the period of the internal TMR0 interrupt,
; used in both RX- and TX mode. 
;*****************************************************************************

;*****************************************************************************
;* Fosc = 20 MHz							     *
;*****************************************************************************
;* Data rate * TIMING_RX  * Rate_RX * Error  * TIMING_TX  * Rate_TX * Error  *
;*****************************************************************************
;* 9.6 kbps  * 0xE5#      * 0xD0    * 0.160% * 0x84       * 0xD0    * 0.224% *
;* 4.8 kbps  * 0xC5       * 0xD0    * 0.160% * 0x02       * 0xD0    * 0.032% *
;* 2.4 kbps  * 0x84       * 0xD0    * 0.160% * 0xFF       * 0xD1    * 0.064% *
;* 1.2 kbps  * 0x02       * 0xD0    * 0.160% * 0x7F       * 0xD3    * 0.304% *
;* 600 bps   * 0xFF       * 0xD1    * 0.160% * 0x7E       * 0xD4    * 0.152% *
;* 300 bps   * 0xFD       * 0xD2    * 0.032% * 0x7E       * 0xD5    * 0.004% *
;*****************************************************************************
; # Use one NOP instruction in end_interrupt_RX, otherwise remove it.
;
; For other combinations of MCU clock frequencies and data-rates, see
; application note for values and formulas.
;
;*****************************************************************************
; Default values
; 	20 MHz MCU clock, 1.2 kbps data rate
;*****************************************************************************

TIMING_RX		EQU	0x02
TIMING_TX		EQU	0x7F
Rate_RX			EQU	0xD0
Rate_TX			EQU	0xD3


;*****************************************************************************
; These timing values values can be changed to optimize synchronisation and
; data decision for a given application
;
;	A_LIMIT_val 	- Decision limit, if A is smaller than the
; 			  value, signal is 0, else signal is 1
;	A_LIMIT_val2   	- Decision limit while synchronising, if 
;		   	  A is smaller than the value, signal is 
;		    	  0, else signal is 1 (Must be >=5)
;	COUNT_LIMIT_val	- Decides how long the synchronisation
;		    	  part should be. The value indicates how
;		    	  many 1's (A=>A_LIMIT_val2) the MCU must
;			  receive before it is synchronised (Should be >=4)
; 	A_SYNC_LIMIT_hi,  
;	A_SYNC_LIMIT_lo - If A>lo and A<hi for SYNC_LOSS_LIMIT bits, the
;			  receiver declares loss of synchronisation
;	BIT_ERROR_LIMIT_val
;			- How many low-quality bits are
;			  accepted before sync is lost
;			  (Should be >=2)
;*****************************************************************************

A_LIMIT_val		EQU	0x04
A_LIMIT_val2		EQU	0x05
COUNT_LIMIT_val		EQU	0X0A
A_SYNC_LIMIT_hi		EQU	0x05
A_SYNC_LIMIT_lo		EQU	0x03
BIT_ERROR_LIMIT_val	EQU	0x02



;*****************************************************************************
;*****************************************************************************
;******************* PROGRAM START *******************************************
;*****************************************************************************
;*****************************************************************************

            ORG     0x00  		; Location of reset vector        
reset:      GOTO    main		; After reset, go to main program

            ORG     0X04		; Location of interrupt vector
interrupt:  GOTO    ServiceInterrupt	; If interrupt->go to ServiceInterrupt
            ORG     0x50

   
;*****************************************************************************
; Main program
;*****************************************************************************
           
main:                          	
        BCF     STATUS, RP0