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Hi All, I'm trying to write to the Serial Window #1 at regular interval of time (But not successful yet). To generate the time interval i'm using timer0 of 8051 in 16 Bit Timer Mode 0x01 The values are initialized as shown below TH0 = 0xFF TL0 = 0x00 In the given program below, if I comment all the printf statements It works fine, generates accurate delay as needed (as seen in Debug Session). i.e. TL0 starts incrementing for every clock tick and when it reaches 0xFF, the next clock tick sets the overflow flag which in turn calls the ISR (Interrupt_Service_Routine0), wherein I again set the timer's TH0 and TL0 value. But if I uncomment the printf statements in the program (Func1 and Func2), I don't get accurate time delay (as seen in Debug Session). when control reaches Func1 and passes ahead of printf statement the TH0 and TL0 value changes to 0x06 and 0x52 respectively. As I have understood the timer 0 values should be between FF00 to FFFF (as initialized in the Timer_0_Init and Interrupt_Service_Routine0) Please do correct me if my understanding is not correct
Using Keil IDE uVision2 V2.38a Have selected ,b>Generic->8052 (all variants),/b> in the Options for Target in Project Menu The program is as shown below:
/*------------------------------------------------------------------------------ HELLO.C Copyright 1995-1999 Keil Software, Inc. ------------------------------------------------------------------------------*/ #include <REG52.H> /* special function register declarations */ /* for the intended 8051 derivative */ #include <stdio.h> /* prototype declarations for I/O functions */ #ifdef MONITOR51 /* Debugging with Monitor-51 needs */ char code reserve [3] _at_ 0x23; /* space for serial interrupt if */ #endif /* Stop Exection with Serial Intr. */ /* is enabled */ #define FUNC1 3 #define FUNC2 2 sbit Port1Pin0 = P1^0; sbit Port1Pin1 = P1^1; sbit Port1Pin2 = P1^2; sbit Port1Pin3 = P1^3; unsigned short myFlag = 0; unsigned short count = 0; /* --------------------------------------------------------- */ //Functions (Func1 and Func2)to be called from ISR void Func1() { // printf("Func1\n"); Port1Pin0 = 1; Port1Pin1 = 0; Port1Pin2 = 1; Port1Pin3 = 0; } void Func2() { // printf("Func2\n"); Port1Pin0 = 1; Port1Pin1 = 0; Port1Pin2 = 0; Port1Pin3 = 0; } /* --------------------------------------------------------- */ //Initializing TImer0 void Timer_0_Init(void) { TMOD |= 0x01; TL0 = 0x00; TH0 = 0xFF; ET0 = 1; TR0 = 1; EA = 1; } /*----------------------------------------------------------*/ //ISR for Timer 0 void Interrupt_Service_Routine0(void) interrupt 1 { TR0 = 0; //Deactivate Timer 0 TL0 = 0x00; //Setting timer Initial value again TH0 = 0xFF; //Setting timer Initial value again TF0 = 0; //Set Timer Overflow Flag to 0 TR0 = 1; //Activate Timer 0 ++count; if (myFlag == 0 && count > FUNC1) { //Call Func1 Func1(); myFlag = 1; count = 0; } else if (myFlag == 1 && count > FUNC2) { //Call Func2 Func2(); myFlag = 0; count = 0; } } /*------------------------------------------------------------*/ void main(void) { /*------------------------------------------------ Setup the serial port for 1200 baud at 16MHz. ------------------------------------------------*/ #ifndef MONITOR51 SCON = 0x50; /* SCON: mode 1, 8-bit UART, enable rcvr */ TMOD |= 0x20; /* TMOD: timer 1, mode 2, 8-bit reload */ TH1 = 221; /* TH1: reload value for 1200 baud @ 16MHz */ TR1 = 1; /* TR1: timer 1 run */ TI = 1; /* TI: set TI to send first char of UART */ #endif Timer_0_Init(); while(1) { //Do Nothing, wait for Timer overflow which inturn calls ISR ; } }
Thanks for your Time and Help
How can you (in sardinespeak) state "You can successfully printf() from an ISR" without knowing if the OPs UART is interrupt driven or not?
That information is all readily available in the code the OP posted. However, these details are irrelevant - none of those things prevent one from being able to successfully printf() from an ISR.
since when ?
The first 'C' compiler for the 8051.
One example of a relevant detail is that if putchar is ISR driven you can't. DO NOTE the MCU: above.
Well, it is possible that the variant is specified somewhere in this thread and I've missed it, but I'm assuming that it's a pretty straightforward 8051.
I'm interested in your idea of an "ISR driven" putchar(). Here's a fairly generic putchar() implementation for interrupt driven serial communications:
/*------------------------------------------------------------------------------ ------------------------------------------------------------------------------*/ #pragma disable char com_putchar ( unsigned char c) { /*------------------------------------------------ If the buffer is full, return an error value. ------------------------------------------------*/ if (com_tbuflen () >= TBUF_SIZE) return (-1); /*------------------------------------------------ Add the data to the transmit buffer. If the transmit interrupt is disabled, then enable it. ------------------------------------------------*/ tbuf [t_in & (TBUF_SIZE - 1)] = c; t_in++; if (ti_restart) { ti_restart = 0; TI = 1; /* generate transmit interrupt */ } return (0); }
Could you give me some idea of how putchar() might be "ISR driven" and how that would prevent one from successfully calling printf() from an ISR?
In most cases printf() from an ISR will lead to some other ISR not being serviced in a timely fashion or the ISR with the printf being constantly seviced i.e. it takes so long to execute that it is activated again before it is done.
Ok, there's ramification number 1 for your list.
Putting a printf in an ISR is an abhorrent violation if the KISS principle (keep ISRs short & simple)
Last time I heard KISS it meant 'Keep It Simple Stupid' which seemed rather more snappy.
One point to the above is that the problems can show up in an intermittent way making the debugging (of what is wrong in the first place) virtually impossible.
This is why one needs to be aware of the ramifications.
Could you give me some idea of how putchar() might be "ISR driven" and how that would prevent one from successfully calling printf() from an ISR? ... then each and every point you have made is moot
Erik
... then each and every point you have made is moot
Is that really your best attempt at answering the question?
attempt, no, but if you do not know how printf/putchar can be ISR driven, then your postings in this thread are invalid.
Of course, if you are one of those that can only work with waitI/O, then I understand your problem.
In a sane interrupt driven serial comms implementation neither printf() nor putchar() are interrupt driven. printf() calls putchar(), and putchar() places the character passed to it in a buffer. If necessary putchar() sets TI to stimulate the first serial interrupt. That's it - neither printf() nor putchar() are driven by an ISR nor does this prevent printf() being called from an ISR.
If you think you can show otherwise please do.
I am SOOOOO sorry, what you write I can ONLY read as "printf/putchar can be ISR driven", if you want me to convert to your verbiose babbeling style, I refuse.
If necessary putchar() sets TI to stimulate the first serial interrupt.
Your attempts to get out of this one with your skin intact are becoming increasingly amusing. By your argument this:
void main(void) { EA=1; ES=1; TI=1; while(1); }
is an interrupt driven main.
nothing else
i be thinking YOU now be sitting in the corner with YOUR hat on ;)
Oh, I see. So I suppose this statement of yours does not mean what appears to?
One example of a relevant detail is that if putchar is ISR driven you can't [printf() successfully from an ISR].
since I have no desire to do so.
You babble about C standards, C this, C that so instead of saying serial comms, I said putchar
instead of saying serial comms, I said putchar
No problem. Explain why you think this is true:
One example of a relevant detail is that if [serial comms are] ISR driven you can't [printf() successfully from an ISR].
I guess you must be having a very long think about this.
I just got tired of your blabber and decided to let this therad die
I guess you must be having a very long think about this. naah, it is crystal clear, but if you can not figure it out, so be it.
DO NOT ask me to do your thinking for you!!!!!!!
naah, it is crystal clear, but if you can not figure it out, so be it.
I can't figure it out, that's why I'm asking you to explain it. I need to draw on your expertise with printf() and interrupt driven putchar() to further my understanding.
Ah, but my powers of thought are not up to the task. Educate me master!
re "expertise with printf() and putchar()" I totally leave that to you who proclaim way more 'C' expertise than I have.
Since you ever so often have pushed 'read' I'll return the favor
re interrupt conflicts/inteference, read here (ch3)
Chapter 1 - 80C51 Family Architecture: www.nxp.com/.../80C51_FAM_ARCH_1.pdf Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: www.nxp.com/.../80C51_FAM_PROG_GUIDE_1.pdf Chapter 3 - 80C51 Family Hardware Description: www.nxp.com/.../80C51_FAM_HARDWARE_1.pdf