Osctune

[retepsnikrep]

18F2620 hserout baud rates off consistently.

I'm using hserout to send data to a PC running the old plx-daq excel data acquisition macro/control.
It's worked in the past but i haven't used it for a long time.

I have cranked up my pic speed to 32mhz using the PLL etc and that's confirmed by the simple flashing 1hz led trick.

I set the ESUART with data from PicMulticalc using 32mhz as osc speed.

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 0
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 51 ' 38400 Baud @ 32MHz, 0.16%
SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator

The pic is transmitting data correctly but when checked with my logic probe I can see the baud rate is off.

At 38400 it is actually 40000
At 19200 it is 20000
At 9600 it is 10000

Seems very consistent and perhaps the windows serial port can't tolerate this error?

Do you thing this is a ESUART register setting problem or a wayward oscillator that needs OSCTUNE tweaking?

[HenrikOlsson]

I have a bunch of boards, all on a RS485 bus, all running the same code, and ONE board had to have its baudrate tweaked because it was off (I don't remember if I tweaked OSCTUNE or BAUDCON) so I'm leaning towards the oscillator not being quite where it should be.

Do you have another PIC of the same type to try with?

To verify if it's the oscillator, try generating a pulse with a known width and measure it.

/Henrik.

[retepsnikrep]

I tried another pic that produced exactly the same results

The pic is transmitting data correctly but when checked with my logic probe I can see the baud rate is off.

At 38400 it is actually 40000
At 19200 it is 20000
At 9600 it is 10000

[richard]

you're sending a start bit, 8 bits of data and a stop bit all encoded as one symbol ie 10 bits .
@say 9600 symbols per sec that yields a bit time of 10.4uS.
how and what are you measuring ?
logic probe ? do you mean logic analyser
have you left off the start or stop bit in your calcs ?
10 bits @ 10.4uS /bit = 9600 baud
9 bits @ 10.4uS /bit = 10000 baud

[retepsnikrep]

I'm measuring using Saleae Logic software.
It reports the values I mentioned when using autobaud to detect the rate.

https://www.saleae.com/downloads.

I used to have this working but the problem is I don't know if it is the transmitter Hserout or receiver plx-daq is not working?

The data looks correctly constructed with the logic analyser monitoring it.

My config for reference is

#CONFIG
__CONFIG _CONFIG1H, _OSC_INTIO67_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
__CONFIG _CONFIG2L, _PWRT_OFF_2L & _BOREN_OFF_2L & _BORV_3_2L
__CONFIG _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
__CONFIG _CONFIG3H, _CCP2MX_PORTC_3H & _PBADEN_OFF_3H & _LPT1OSC_OFF_3H & _MCLRE_OFF_3H
__CONFIG _CONFIG4L, _STVREN_OFF_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L
__CONFIG _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L & _CP2_OFF_5L & _CP3_OFF_5L
__CONFIG _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
__CONFIG _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L & _WRT2_OFF_6L & _WRT3_OFF_6L
__CONFIG _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
__CONFIG _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L & _EBTR2_OFF_7L & _EBTR3_OFF_7L
__CONFIG _CONFIG7H, _EBTRB_OFF_7H
#ENDCONFIG

DEFINE OSC 32 '32mhz Clock
OSCCON = %01110000 'Internal 32 mhz Osc and stable
OSCTUNE = %01000000 'Enable PLL 8mhz x 4
WDTCON = %00010101 'Set watchdog Timer for 1 second
CMCON = %00000111 'Comparators Off
CVRCON = %00000000 'CvRef Powered Down
CCP1CON= %00001100 'CCP1 Module PWM Mode
CCP2CON= %00000000 'CCP2 Module Disabled
HLVDCON= %00000000 'HLVCON Disabled
T1CON = %00110000 '$30 = Prescaler 1:8, TMR1 OFF
TRISA = %00001011 'SET PORTA0, A1 & A3 AS INPUTS, REST AS OUTPUTS
TRISB = %00000000 'SET PORTB AS OUTPUTS
TRISC = %10011000 'SET PORTC AS OUTPUTS EXCEPT PORT C3,C4 & C7
ADCON0 = %00000001 'SETUP ADC & ENABLE ADC MODULE on AN0
ADCON1 = %00001110 'SETUP ADC SET REFV to VDD & VSS AN0
ADCON2 = %00100010 'SETUP ADC FOSC/32 LEFT JUSTIFY TAD 8

DEFINE LCD_DREG PORTB 'PORTB is LCD data port
DEFINE LCD_DBIT 0 'PORTB.0 is the data LSB
DEFINE LCD_RSREG PORTC 'RS is connected to PORTC.0
DEFINE LCD_RSBIT 0
DEFINE LCD_EREG PORTC 'EN is connected to PORTC.1
DEFINE LCD_EBIT 1
DEFINE LCD_BITS 8 '8 lines of data are used
DEFINE LCD_LINES 4 'It is a 4-line display
DEFINE LCD_COMMANDUS 1500 'Use 1500uS command delay
DEFINE LCD_DATAUS 44 'Use 44uS data delay

DEFINE ADC_BITS 8 'Set number of bits in result
DEFINE ADC_CLOCK 3 'Set Clock source (3 = rc)
DEFINE ADC_SAMPLEUS 50 'Set sampling time in uS

DEFINE CCP1_REG PORTC 'HPWM channel 1 pin Port C Backlight PWM Driver
DEFINE CCP1_BIT 2 'HPWM channel 1 pin Bit 2

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 0
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 51 ' 38400 Baud @ 32MHz, 0.16%
SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator

[retepsnikrep]

Closure on my problem. I found the reciever i was using wanted idle low data not idle high... Arrrggggg.. I was sure it was high..

Thanks for the advice. The transmitter was working correctly after all..