Firefly 16F88 RS232 problem - Electronic Circuits Projects Diagrams Free

futz · 22nd February 2008, 08:43 AM

I've written code to send text from the Firefly to my PC using the AUSART. First odd thing I noticed was that it worked fine when run slow in the debugger, but sent nothing when run at full speed.

I finally found that if I put a short delay right after setting SPBRG during the init, it works normally. I've never had to do this before. Is it something specific to the Firefly or the 16F88, or have I just been lucky up to now with 16F's?

Mike, K8LH · 22nd February 2008, 09:44 AM

Are you using the INTOSC? If so, this is a symptom I've seen on several different PIC devices including the 16F88.

On my 16F88 boot-loader I actually include an additional delay after testing the oscillator stable flag before using the UART.

Mike

futz · 22nd February 2008, 04:29 PM

Quote:

Originally Posted by Mike, K8LH

Are you using the INTOSC? If so, this is a symptom I've seen on several different PIC devices including the 16F88.

On my 16F88 boot-loader I actually include an additional delay after testing the oscillator stable flag before using the UART.

Mike

Hey! That could be it. I am using internal osc. The program is tiny and gets right to business doing the one thing it does - spit data out the RS232. I'll take out the delay and put a osc-stable check and see what happens.

futz · 23rd February 2008, 02:54 AM

Yup, that cured it. No delay needed. Just a quicky little oscillator-stable loop, waiting for the IOFS bit to get set.

Code:

init
	banksel	OSCCON		;bank 1
	movlw	b'01110110'	;internal 8mhz osc
	movwf	OSCCON
stable	btfss	OSCCON,IOFS	;oscillator stable?
	goto	stable		;no, wait
	.
	.
	.

I guess I must have always used crystals before, and they start up faster, or I had bigger code that did other things while the osc stabilized.

blueroomelectronics · 23rd February 2008, 03:19 AM

I wonder if that applies to all PICs with an IOFS bit. Good thing to know.
Nice photos too futz

futz · 23rd February 2008, 04:23 AM

Quote:

Originally Posted by blueroomelectronics

Nice photos too futz

Playing with my nice new Canon A650 IS.

Costco just recently had them on sale for $100 off, so I grabbed one. All previous pics came from my Canon A80.

Mike, K8LH · 23rd February 2008, 01:04 PM

Quote:

Originally Posted by blueroomelectronics

I wonder if that applies to all PICs with an IOFS bit. Good thing to know.

I experienced the same symptom when using INTOSC on my 18F2520 and 18F2620 bootloaders too. It seems to take just a tiny bit longer than "oscillator stable" for the oscillator to be "on frequency"...

Mike

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22nd February 2008, 08:43 AM	#1
futz	Firefly 16F88 RS232 problem I've written code to send text from the Firefly to my PC using the AUSART. First odd thing I noticed was that it worked fine when run slow in the debugger, but sent nothing when run at full speed. I finally found that if I put a short delay right after setting SPBRG during the init, it works normally. I've never had to do this before. Is it something specific to the Firefly or the 16F88, or have I just been lucky up to now with 16F's? __________________ ========================= Futz's Microcontrollers & Robotics ========================= Last edited by futz; 22nd February 2008 at 08:50 AM.

22nd February 2008, 09:44 AM	#2
Mike, K8LH	Are you using the INTOSC? If so, this is a symptom I've seen on several different PIC devices including the 16F88. On my 16F88 boot-loader I actually include an additional delay after testing the oscillator stable flag before using the UART. Mike

23rd February 2008, 02:54 AM	#4
futz	Yup, that cured it. No delay needed. Just a quicky little oscillator-stable loop, waiting for the IOFS bit to get set. Code: init banksel OSCCON ;bank 1 movlw b'01110110' ;internal 8mhz osc movwf OSCCON stable btfss OSCCON,IOFS ;oscillator stable? goto stable ;no, wait . . . I guess I must have always used crystals before, and they start up faster, or I had bigger code that did other things while the osc stabilized. __________________ ========================= Futz's Microcontrollers & Robotics =========================

23rd February 2008, 03:19 AM	#5
blueroomelectronics	I wonder if that applies to all PICs with an IOFS bit. Good thing to know. Nice photos too futz __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/