Subject:
PIC interrupt driven usart driver
From:
Michael Shiloh ####@####.####
Date:
30 Oct 1999 06:11:21 -0000
Message-Id: <199910300604.XAA03531@ktura.wrs.com>
(sorry if this is a repeat; i'm not sure my earlier post got out.)
hello,
i'm writing an interrupt driven driver for the usart on
a 16C63A, and i'm having some trouble.
i first wrote the transmitter, and tested it by repeatedly spitting
out some character. works fine.
next i wrote the receiver, and tested it by echoing the received character
out back out via the transmitter. in this case i use the transmitter
in non-interrupt mode so that i don't get interrupted again right away.
what i see are garbled characters. for every key i press, i get echoed
back the wrong character. for a given key, it is always the same character
e.g. if i press 'm' i always get 'i'.
i can see no pattern, e.g. the mapping doesn't seem to be explained by
a bit stuck one way or the other.
one thing that occurred to me that i haven't tested yet, is that
currently i copy the character directly out of the RCREG into the TXREG;
tonight i'll try putting it in a temporary variable in between.
if anyone else is interested, i would be more than happy to make
the finished driver publicly available.
also, does anyone know if Microchip makes a flash part with the
same usart? i couldn't find one but i may have not seen it.
i'm writing in C, using the C2C compiler, gpasm, on a linux platform.
my C code follows, with the assembly listing below.
any comments and suggestions will be appreciated.
thanks,
michael shiloh
####@####.####
- - - - - - - - 8< - - - - - cut here - - - - - - - - 8< - - - - -
#define PORT_A_DIR 0x0 /* all are outputs */
#define PORT_B_DIR 0xf0 /* bits 7-4 are inputs */
#define PORT_C_DIR 0xc0 /* bits 7-6 must be set for usart mode*/
/* bits in the interrupt control register, INTCON */
#define t0if_bitmask 0x04 /* timer 0 interrupt flag bitmask */
/* bits in the peripheral interrupt register, PIR1 */
#define txif_bitnum 4 /* usart transmit interrupt flag bit number */
#define txif_bitmask 0x10 /* usart transmit interrupt flag bit mask */
#define rcif_bitnum 5 /* usart receive interrupt flag bit number */
#define rcif_bitmask 0x20 /* usart receive interrupt flag bit mask */
char TXSTA@0x98;
char SPBRG@0x99;
char RCSTA@0x18;
char TXREG@0x19;
char RCREG@0x1A;
char PIR1@0x0C;
char PIE1@0x8C;
void interrupt( void )
{
if (INTCON & t0if_bitmask)
{
/* perform whatever gets done here */
clear_bit( INTCON, T0IF ); //clear TMR0 overflow flag
}
if (PIR1 & txif_bitmask)
{
/* TXREG = 'm'; */
clear_bit( PIR1, txif_bitnum ); //clear transmit interrupt flag
}
if (PIR1 & rcif_bitmask)
{
TXREG = RCREG;
clear_bit( PIR1, rcif_bitnum ); //clear receive interrupt flag
}
}
main()
{
/* disable all interrupts */
disable_interrupt( GIE );
disable_interrupt(PEIE);
disable_interrupt(T0IE);
disable_interrupt(INTE);
disable_interrupt(RBIE);
disable_interrupt(T0IF);
disable_interrupt(INTF);
disable_interrupt(RBIF);
set_bit( STATUS, RP0 ); /* bank 1 */
OPTION_REG = 0;
SPBRG = 25; /* with BRGH = 0 and 4 Mhz xtal; 2400 baud */
clear_bit( TXSTA, BRGH ); /* low speed */
clear_bit( TXSTA, SYNC ); /* async mode */
set_bit( PIE1, TXIE); /* enable transmit interrupts */
clear_bit( PIE1, TXIE); /* DISenable transmit interrupts */
set_bit( PIE1, RCIE); /* enable receive interrupts */
set_tris_a( PORT_A_DIR );
set_tris_b( PORT_B_DIR );
set_tris_c( PORT_C_DIR );
clear_bit( STATUS, RP0 ); /* bank 0 */
output_port_a( 0 );
output_port_b( 0 );
output_port_c( 0 );
enable_interrupt( GIE );
enable_interrupt( T0IE ); /* enable TMR0 overflow bit */
enable_interrupt( PEIE ); /* enable peripheral interrupts */
set_bit (RCSTA, SPEN ); /* enable serial port */
set_bit (RCSTA, CREN); /* enable receiver */
set_bit( STATUS, RP0 );
set_bit (TXSTA, TXEN); /* enable transmitter */
clear_bit( STATUS, RP0 );
/* send out a start char, so i know we're alive */
TXREG = 'M';
while (1)
{
}
}
gpasm 0.0.7 alpha uartInter.asm9-29-1999 11:31:55 PAGE 1
Variables *****************************************
LOC OBJECT CODE LINE SOURCE TEXT
VALUE
00001 ; This file was generated by C2C-plus compiler version 3.26e
00002
0000 00001 LIST
00002 ; P16C63A.INC Standard Header File, Version 1.00 Microchip Technology, Inc.
0000 00284 LIST
00003 include "/home/michaels/c2c30/h/p16c63.h"
00004 title "Variables *****************************************"
00000020 00005 __int_save_cont_W equ 0x20
00000021 00006 __int_save_cont_STATUS equ 0x21
00000098 00007 _TXSTA equ 0x98
00000099 00008 _SPBRG equ 0x99
00000018 00009 _RCSTA equ 0x18
00000019 00010 _TXREG equ 0x19
0000001A 00011 _RCREG equ 0x1a
0000000C 00012 _PIR1 equ 0x0c
0000008C 00013 _PIE1 equ 0x8c
0000 00014 ORG 0
0000 2817 00015 goto start__code
00016
0004 00017 ORG 4
0004 00018 _interrupt
0004 00019 _interrupt__code
0004 00A0 00020 movwf __int_save_cont_W
0005 0EA0 00021 swapf __int_save_cont_W, F
0006 0E03 00022 swapf STATUS, W
0007 00A1 00023 movwf __int_save_cont_STATUS
0008 1D0B 00024 btfss INTCON, 2
0009 280B 00025 goto label_0000
000A 110B 00026 bcf INTCON, T0IF
000B 00027 label_0000
000B 1E0C 00028 btfss _PIR1, 4
000C 280E 00029 goto label_0001
000D 120C 00030 bcf _PIR1, D'4'
000E 00031 label_0001
000E 1E8C 00032 btfss _PIR1, 5
000F 2813 00033 goto label_0002
0010 081A 00034 movf _RCREG, W
0011 0099 00035 movwf _TXREG
0012 128C 00036 bcf _PIR1, D'5'
0013 00037 label_0002
0013 0E21 00038 swapf __int_save_cont_STATUS, W
0014 0083 00039 movwf STATUS
0015 0E20 00040 swapf __int_save_cont_W, W
0016 0009 00041 retfie
0017 00042 _interrupt__end
00043
0017 00044 start__code
0017 00045 _main__code
0017 138B 00046 bcf INTCON, GIE
0018 130B 00047 bcf INTCON, PEIE
0019 128B 00048 bcf INTCON, T0IE
001A 120B 00049 bcf INTCON, INTE
001B 118B 00050 bcf INTCON, RBIE
001C 110B 00051 bcf INTCON, T0IF
001D 108B 00052 bcf INTCON, INTF
gpasm 0.0.7 alpha uartInter.asm9-29-1999 11:31:55 PAGE 2
Variables *****************************************
001E 100B 00053 bcf INTCON, RBIF
001F 1683 00054 bsf STATUS, RP0
0020 0181 00055 clrf OPTION_REG
0021 3019 00056 movlw D'25'
0022 0099 00057 movwf _SPBRG
0023 1118 00058 bcf _TXSTA, BRGH
0024 1218 00059 bcf _TXSTA, SYNC
0025 160C 00060 bsf _PIE1, TXIE
0026 120C 00061 bcf _PIE1, TXIE
0027 168C 00062 bsf _PIE1, RCIE
0028 3000 00063 movlw D'0'
0029 0085 00064 movwf TRISA
002A 30F0 00065 movlw D'240'
002B 0086 00066 movwf TRISB
002C 30C0 00067 movlw D'192'
002D 0087 00068 movwf TRISC
002E 1283 00069 bcf STATUS, RP0
002F 0185 00070 clrf PORTA
0030 0186 00071 clrf PORTB
0031 0187 00072 clrf PORTC
0032 178B 00073 bsf INTCON, GIE
0033 168B 00074 bsf INTCON, T0IE
0034 170B 00075 bsf INTCON, PEIE
0035 1798 00076 bsf _RCSTA, SPEN
0036 1618 00077 bsf _RCSTA, CREN
0037 1683 00078 bsf STATUS, RP0
0038 1698 00079 bsf _TXSTA, TXEN
0039 1283 00080 bcf STATUS, RP0
003A 304D 00081 movlw D'77'
003B 0099 00082 movwf _TXREG
003C 00083 label_0003
003C 283C 00084 goto label_0003
003D 00085 label_0004
003D 00086 _main__end
gpasm 0.0.7 alpha uartInter.asm9-29-1999 11:31:55 PAGE 3
Variables *****************************************
SYMBOL TABLE
LABEL VALUE
BF 00000000
BRGH 00000002
C 00000000
CCP1CON 00000017
CCP1IE 00000002
CCP1IF 00000002
CCP1M0 00000000
CCP1M1 00000001
CCP1M2 00000002
CCP1M3 00000003
CCP1X 00000005
CCP1Y 00000004
CCP2CON 0000001D
CCP2IE 00000000
CCP2IF 00000000
CCP2M0 00000000
CCP2M1 00000001
CCP2M2 00000002
CCP2M3 00000003
CCP2X 00000005
CCP2Y 00000004
CCPR1H 00000016
CCPR1L 00000015
CCPR2H 0000001C
CCPR2L 0000001B
CKP 00000004
CREN 00000004
CSRC 00000007
D 00000005
DATA_ADDRESS 00000005
DC 00000001
D_A 00000005
F 00000001
FERR 00000002
FSR 00000004
GIE 00000007
I2C_DATA 00000005
I2C_READ 00000002
I2C_START 00000003
I2C_STOP 00000004
INDF 00000000
INTCON 0000000B
INTE 00000004
INTEDG 00000006
INTF 00000001
IRP 00000007
NOT_A 00000005
NOT_ADDRESS 00000005
NOT_BO 00000000
NOT_BOR 00000000
NOT_PD 00000003
NOT_POR 00000001
NOT_RBPU 00000007
NOT_RC8 00000006
gpasm 0.0.7 alpha uartInter.asm9-29-1999 11:31:55 PAGE 4
Variables *****************************************
NOT_T1SYNC 00000002
NOT_TO 00000004
NOT_TX8 00000006
NOT_W 00000002
NOT_WRITE 00000002
OERR 00000001
OPTION_REG 00000081
P 00000004
PCL 00000002
PCLATH 0000000A
PCON 0000008E
PEIE 00000006
PIE1 0000008C
PIE2 0000008D
PIR1 0000000C
PIR2 0000000D
PORTA 00000005
PORTB 00000006
PORTC 00000007
PR2 00000092
PS0 00000000
PS1 00000001
PS2 00000002
PSA 00000003
R 00000002
RBIE 00000003
RBIF 00000000
RC8_9 00000006
RC9 00000006
RCD8 00000000
RCIE 00000005
RCIF 00000005
RCREG 0000001A
RCSTA 00000018
READ_WRITE 00000002
RP0 00000005
RP1 00000006
RX9 00000006
RX9D 00000000
R_W 00000002
S 00000003
SPBRG 00000099
SPEN 00000007
SREN 00000005
SSPADD 00000093
SSPBUF 00000013
SSPCON 00000014
SSPEN 00000005
SSPIE 00000003
SSPIF 00000003
SSPM0 00000000
SSPM1 00000001
SSPM2 00000002
SSPM3 00000003
SSPOV 00000006
SSPSTAT 00000094
STATUS 00000003
SYNC 00000004
T0CS 00000005
gpasm 0.0.7 alpha uartInter.asm9-29-1999 11:31:55 PAGE 5
Variables *****************************************
T0IE 00000005
T0IF 00000002
T0SE 00000004
T1CKPS0 00000004
T1CKPS1 00000005
T1CON 00000010
T1INSYNC 00000002
T1OSCEN 00000003
T2CKPS0 00000000
T2CKPS1 00000001
T2CON 00000012
TMR0 00000001
TMR1CS 00000001
TMR1H 0000000F
TMR1IE 00000000
TMR1IF 00000000
TMR1L 0000000E
TMR1ON 00000000
TMR2 00000011
TMR2IE 00000001
TMR2IF 00000001
TMR2ON 00000002
TOUTPS0 00000003
TOUTPS1 00000004
TOUTPS2 00000005
TOUTPS3 00000006
TRISA 00000085
TRISB 00000086
TRISC 00000087
TRMT 00000001
TX8_9 00000006
TX9 00000006
TX9D 00000000
TXD8 00000000
TXEN 00000005
TXIE 00000004
TXIF 00000004
TXREG 00000019
TXSTA 00000098
UA 00000001
W 00000000
WCOL 00000007
Z 00000002
_BODEN_OFF 00003FBF
_BODEN_ON 00003FFF
_CP_50 00002AEF
_CP_75 000015DF
_CP_ALL 000000CF
_CP_OFF 00003FFF
_HS_OSC 00003FFE
_LP_OSC 00003FFC
_PIE1 0000008C
_PIR1 0000000C
_PWRTE_OFF 00003FFF
_PWRTE_ON 00003FF7
_RCREG 0000001A
_RCSTA 00000018
_RC_OSC 00003FFF
_SPBRG 00000099
gpasm 0.0.7 alpha uartInter.asm9-29-1999 11:31:55 PAGE 6
Variables *****************************************
_TXREG 00000019
_TXSTA 00000098
_WDT_OFF 00003FFB
_WDT_ON 00003FFF
_XT_OSC 00003FFD
__int_save_cont_STATUS 00000021
__int_save_cont_W 00000020
_interrupt 00000004
_interrupt__code 00000004
_interrupt__end 00000017
_main__code 00000017
_main__end 0000003D
label_0000 0000000B
label_0001 0000000E
label_0002 00000013
label_0003 0000003C
label_0004 0000003D
start__code 00000017
Errors : 0
Warnings : 0
Messages : 0
