Hello world not working (16F74)

[imhereithink]

Hi guys,

im trying to get the usart of my 16F74 to work, to test it i am sending out the good old " HELLO WORLD" but i am getting nothing through on my hyper terminal, and on my data comms tester im getting utter garbage I have attached the code for you to give me some helpful tips on where i might be going wrong.

Thanks in advance

 

[Gayan Soyza]

For me your DELAY is not good.Try replace the delay with a simple delay.without taking TMR0.
Just a simple delay like

	decfsz	DEL,F
	goto	$-1
	return

 

[eng1]

Shouldn't you configure bit 6 of PORTC as output?
Have you tried receiving data from the pc?
Are you using a max232 or similar?

 

[crazyGSM]

Configure UART for 9600 bps (0.16% Error)


The Hiperterminal need the same config as PIC.

like @ Gayan Soyza say

"For me your DELAY is not good"


and don't forget the RS232 converter using a MAX232
something like this

**broken link removed**

 

[imhereithink]

Thanks for the comments guys,

I just tried simulating the delay routine and its getting hung up in their, i will try the simpler method as suggested and let you know how it goes
Also i am using the max 233 chip and the hyperterminal is set up the same as what im sending out.

Cheers

 

[imhereithink]

Right i just tried a simple delay:

DELAY MOVLW d'50'
MOVWF count1
lp1 DECF count1,F
btfss STATUS,Z
goto lp1
return

I tried simulating this but it never counts out, it just keeps looping any ideas as to whats wrong with this?

 

[eng1]

Use the delay code generator on the PICList. Here's the link:


Have you configured the TRISC register as I said earlier?

 

[imhereithink]

eng1 you are right, i never set portc up correctly, i assumed the pins would be set through setting the usart up . . . i assumed wrong That will teach me for not reading the data sheet thouroghly. I will give that a shot and see what happens.

Thanks

 

[Pommie]

Both RX and TX have to be set to input to configure the UART. I would get rid of the delay and just wait for TXIF to be set before writing to TXREG.

Have you set Hyperterminal to use no flow control?

Mike.

 

[eng1]

Both RX and TX have to be set to input to configure the UART. I would get rid of the delay and just wait for TXIF to be set before writing to TXREG.

Mike, you are correct. I've just checked an old program I wrote and they're both set to input. Honestly I usually use software routienes to do RS-232
So that isn't be the problem with the program, because TRISC is 0xFF on reset...



I would check the value that is loaded into the SPBRG register! fosc is 20 MHz, isn't it?

 

[ericgibbs]

Hi guys,

im trying to get the usart of my 16F74 to work, to test it i am sending out the good old " HELLO WORLD" but i am getting nothing through on my hyper terminal, and on my data comms tester im getting utter garbage I have attached the code for you to give me some helpful tips on where i might be going wrong.

Thanks in advance

hi,
Check the baud rate divider, you have 25?
>>>>>
#include <p16F74.inc> ;processor specific variable definitions
__config _HS_OSC & _WDT_OFF & _PWRTE_ON & _CP_OFF & _BODEN_OFF
;Configuration bits set as: Oscillator EXTERNAL 20MHz
BSF STATUS, RP0 ; Select Bank 1
BSF TXSTA, BRGH ; Enable high speed baud generator
MOVLW D'25' Configure UART for 9600 bps (0.16% Error)
MOVWF SPBRG

 

[eng1]

Hi Eric, I too noticed that... shouldn't it be 129?
The initialization would be correct for a 4 MHz crystal.

 

[ericgibbs]

Hi Eric, I too noticed that... shouldn't it be 129?
The initialization would be correct for a 4 MHz crystal.

hi eng1,
I agree, its '25' for a 4MHz xtal and '129' for 20MHz.

Eric

 

[imhereithink]

Thanks for pointing out all the silly mistakes guys, i totally forgot to change the baud rate divider, i used the setup from the 16F627 which ran 4MHz
Iv also taken out the delay and used this instead as suggested:

MOVLW D'72' ;H
MOVWF TXREG
TEST1 BTFSS TXSTA,TXIF
GOTO TEST1

Now i just need to test it out. Thanks again guys you've ben a big help

 

[imhereithink]

I just went and tested it, and im getting most of the hello world message but theres a few extra characters thrown in from somewhere, this is what im getting through on the coms tester:
HHEMLLLNO@_&WWOCR^LDD
The other thing is im not getting any data through the hyper terminal, iv got this set to:

Bits per second: 9600
Data bits: 8
Parity: None
Stop bits: 1
Flow control: None

Any ideas?

Thanks again

 

[ericgibbs]

I just went and tested it, and im getting most of the hello world message but theres a few extra characters thrown in from somewhere, this is what im getting through on the coms tester:
HHEMLLLNO@_&WWOCR^LDD
The other thing is im not getting any data through the hyper terminal, iv got this set to:

Bits per second: 9600
Data bits: 8
Parity: None
Stop bits: 1
Flow control: None

Any ideas?

Thanks again

Hi Greg,
Try this, runs OK on my Oshonsoft simulator.

Eric

 

[imhereithink]

Hi eric,

I tried your code to no avail, it only sends out H permenantly
I also tried ammending my HW.asm since i noticed i was using the wrong register for the TXIF flag, i was using TXSTA when i should have been using PIR1
When i ran this program it now sends out:HLOO constantly. It seems that the data is being overwritten in the TXREG buffer? Am i testing the TXIF flag correctly?

 

[ericgibbs]

Hi eric,

I tried your code to no avail, it only sends out H permenantly
I also tried ammending my HW.asm since i noticed i was using the wrong register for the TXIF flag, i was using TXSTA when i should have been using PIR1
When i ran this program it now sends out:HLOO constantly. It seems that the data is being overwritten in the TXREG buffer? Am i testing the TXIF flag correctly?

hi,
I use this subr on all my PIC prgms with no problems

;---- SERIAL UART ----
; Hardware Serial Communication Routines
TXRDY:
BTFSC PIR1,TXIF
GOTO XMIT1
GOTO TXRDY;busy,so loop
XMIT1:
MOVWF TXREG;send
RETURN

Are you sure that the receiving PC is OK?

Eric

 

[imhereithink]

Are you sure that the receiving PC is OK?

Im beginning to wander lol I will try and use that subroutine in the HW.asm and see how far i get, if not i will try and use this on another pc.

Cheers

 

[Nigel Goodwin]

hi,
I use this subr on all my PIC prgms with no problems

;---- SERIAL UART ----
; Hardware Serial Communication Routines
TXRDY:
BTFSC PIR1,TXIF
GOTO XMIT1
GOTO TXRDY;busy,so loop
XMIT1:
MOVWF TXREG;send
RETURN

Why two goto's?.

Change the BTFSC to BTFSS and delete the GOTO XMIT1

Here are the routines from my RS232 tutorial.

XMIT_RS232  	btfss   PIR1,	TXIF 	      ;xmit buffer empty?
     		GOTO	XMIT_RS232            ;no, wait
     		MOVWF   TXREG		      ;now send
                RETURN

Rcv_RS232   	BTFSS   PIR1,	RCIF 	      ; check for received data
     		GOTO    Rcv_RS232
                MOVF    RCREG,	W
                RETURN