Serial Baudrate 115200

[flotulopex]

Yes, I do use a USB-to-serial interface (FTDI).

I now corrected the BAUDCTL register so as it sends data inverted (no need for a hw inverter anymore).

As far as I understand this register's function, OSCTUNE calibrates the internal oscillator so I don't think it will affect the baud rate generator (I don't know).

BTW, how do I measure a "good" 115200bps signal?

' HSEROUT
 
' PIC 16F690 Fuses
@ __Config _FCMEN_OFF &_IESO_OFF &_BOR_OFF &_CPD_OFF &_CP_OFF &_MCLRE_OFF &_PWRTE_OFF &_WDT_OFF &_HS_OSC
 
OPTION_REG = %10000000 'PORT A&B Pull-Ups (look WPUA & WPUB)
ADCON0     = %00000000 'A/D Module
ANSEL      = %00000000 'Select analog inputs Channels 0 to 7
ANSELH     = %00000000 'Select analog inputs Channels 8 to 11
INTCON     = %00000000 'INTERRUPT Control
'WPUA       = %00000000 'Select PORTA weak pull-ups
'IOCA       = %00000000 'Interrupt On Change selection
CM1CON0    = %00000000 'Comparator1 Module
CM2CON0    = %00000000 'Comparator2 Module
TRISA      = %00000000 'Set Input/Output (0 to 5)
PORTA      = %00000000 'Ports High/Low (0 to 5)
TRISB      = %00000000 'Set Input/Output (4 to 7)
PORTB      = %00000000 'Ports High/Low (4 to 7)
TRISC      = %00000000 'Set Input/Output (0 to 7)
PORTC      = %00000000 'Ports High/Low (0 to 7)
 
'-------------------------------------------------------------------------------
' DEFINEs
DEFINE OSC 20
RCSTA = $90 ' Enable serial port & continuous receive
TXSTA = $24 ' Enable transmit, BRGH = 1
SPBRG = 42 ' 115200 Baud @ 20MHz, 0.94%
BAUDCTL = 24 'Transmit INVERTED data to RB7, Enable 16 bit baudrate generator
 
 
'-------------------------------------------------------------------------------
LED1    var PORTA.2
Counter var word
Counter = 0
 
TEST:
  Toggle led1
  HSEROUT [dec counter,13,10]
  pause 500
  Counter = counter + 1
  goto test
 
  end

[Charles Linquis]

The baud rate generator will be accurate. If the formula says you will get 115KBaud with a 20Mhz oscillator, you will.
If you don't get 115K baud, then you aren't really running at 20Mhz, or the receiving device has an issue.

I mentioned in another post how to measure just how fast your chip is running - without an oscilloscope.

(Turn LED ON)
For X = 1 to 60
Pause 60000
Next X
(Turn LED OFF)

Wait one hour. If your LED goes off in exactly 60 minutes, your chip is running the speed you think it is. Using a
calculator, you can measure the actual frequency to about 0.1%

A useful tool is BRAY's TERMINAL program (Google it). Free, and it lets you set odd baud rates, like 113Kbaud.
or 120Kbaud.