HSerin problems on power up

This is a problem I've encountered for years on several different chips and have always just kind of ignored it. I have a problem using the Hserin command on initial power up. Below is a stripped down version of my code. Basically I power up the chip and wait a little while then send a burst of data. that data is basically ignored, I send a second burst and it is processed as is every burst after. if I hit the reset button every burst is processed, but if I turn off the power and wait a few seconds before powering back up the problem comes back for the first burst of data. I've checked the overflow and framing error bits, and see no problem. There are only a few registers I can even think to look at, but nothing is popping out at me. it seems like it would have to be something obvious.

Code:

---

INCLUDE "DT_INTS-18.bas"      ; Base Interrupt System
INCLUDE "ReEnterPBP-18.bas"    ; Include if using PBP interrupts

Clear
DEFINE        OSC                40                        ' Set Xtal Frequency
DEFINE HSER_CLROERR 1      'will automatically clear overflow errors
       
stream                VAR        BYTE[80]        'the last stream in
view_stream var byte[104]  'outsream converted to patterns                           

a                        VAR        BYTE            'loop counter variable
b                        VAR        BYTE
x                        VAR        BYTE            'loop counter variable
B0                        VAR BYTE
B1                        VAR BYTE
B2                        VAR BYTE
B3                        VAR BYTE
B4                        VAR BYTE
B5          var byte

pattern    var byte
new_stream  var bit

red_LED                  VAR        PORTC.4                                          'red led

CSALL                CON %00000000                        'Chip Select for all chips
CSOFF                CON        %00001111                        'chip select for no chips

CSB0                VAR        PORTB.0
CSB1                VAR        PORTB.1
CSB2                VAR        PORTB.2
CSB3                VAR        PORTB.3

TRISA = %11101100
TRISB = %11110000                        'inputs for upper half switches outputs for lower CS
TRISC = %11001111                        '0-3 for switches, 4-5 for LEDs, 6-7 for serial data
TRISD = 0
TRISE = 0

PORTB = CSOFF
PORTE.0 = 1
PORTE.1 = 1
PORTE.2 = 0

ADCON1 = %00001111

;****************Using Darrel Taylor Interrupts****************************
;----[High Priority Interrupts]--------------------------------------------
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    RX_INT,    _GetData,  PBP,  no
    endm
    INT_CREATE              ;Creates the High Priority interrupt processor
ENDASM

red_LED    = 0                    'turn on red LED

Pause 1000

top:

    TXSTA = $20  ' Enable transmit, BRGH = 0
    SPBRG = 34    ' 1200 Baud @ 0.0%
    SPBRGH = 8
    BAUDCON.3 = 1 ' Enable 16 bit baudrate generator       
    RCSTA = $90  ' Enable serial port & continuous receive
             
        GoSub send_data

countdown:
'count from 9 to 0

        For x = 9 TO 0 STEP - 1
                For a = 0 TO 79
                        stream[a] = x + "0"
                Next a
                GoSub send_data
                Pause 150
        Next x
       
end_countdown:
'check buttons
           
@  INT_ENABLE  RX_INT    ; enable RX_INT interrupts

        RCSTA = $80          'clear CREN
        RCSTA = $90          'Enable receive
 
 
   
mainloop:
       
       
    if new_stream = 1 then
        RCSTA.4 = 0
            RCSTA.4 = 1                'clear over run error
        new_stream = 0               
        GoSub send_data
    endif
 
    GoTo mainloop
 
send_data:

    'this sub will send bit patterns via psp (non interrupt driven) to another chip
       
    Return 
 
       
'---[USART RX - interrupt handler]-----------------------[High Priority]---
GetData:

    hserin 1000,No232,[str stream\80\10] 

    red_LED = red_LED +1        'heartbeat
    new_stream = 1
   
No232:
@ INT_RETURN
       
End

---

Thanks
David

If there's HSERIN/HSEROUT, you should use DEFINEs, unless you just need to write the USART registers.

Code:

---

INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    RX_INT,    _GetData,  PBP,  no

---

You want to reset flags, unless, your program will loop in the ISR forever.

I haven't look the whole thing, but those are the really first thing that jump in my face.

Thanks, I'll give the reset flags a try latter. I can't use defines as the baud rate needs to be user configurable in the field.

Yes you can do it, you define one at the top, then you change it later on the fly by writing SPBRG, RCSTA, TXSTA. Check the datasheet for the recommended sequence.

I finally had a chance to try out your suggestions by putting the defines at the beginning of the program and trying to reset the flag, but I have the same result of garbage in on the first transmission, then clear after that. Any other ideas would be appreciated.

David

It may happen if your transmitter use SEROUT/SEROUT2/DEBUG and the pin idle state is not set before sending the first data.

Post your both code, receiver and transmitter end.

I use a VB program not a pic as the transmitter. I can leave the program running while the pic is powered down. I give the pic a few seconds stabilization time after power up before the next transmission is sent

David

Ok then, modify your VB program to send few garbage character, then a Synch String (let's say OK), and in your ISR use WAIT("OK") . See if this solve your problem.

I'm sure this would work, I just figured I would see if anyone knew why I can't get it to work as expected. It isn't critical to the application, just one of those annoyances I figured most people weren't living with :)