Very simple Q about output

arys · Joined: 09 Mar 2007 Posts: 31

Hi.
I read the manual but still do not understand how to use.
the question is, what is the function to set the port as output and how to use it when to give it high at certain pin/bit.
Laughing

arys · Joined: 09 Mar 2007 Posts: 31

for information, i'm using 16f873 and max232 to interface to PC. Is it possible to send and receive 2 variables from PC to PIC and run at the same time. if not, how to change 2 variables in PIC from VB synchronizely?

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

The usual output functions, such as Output_x(), automatically handle the port direction register.

If you need to use #use fast_io or #use fixed_io to eek out a little more speed, then you will have to use something like Set_tris_x() to handle the direction register yourself. But most code just uses the automatic functions.
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Douglas Kennedy · Joined: 07 Sep 2003 Posts: 755 Location: Florida

The output_high(pin_xxx) and output_low(pin_xxx) work with individual pins.
Ex. output_low(PIN_B0)
You will need to understand this basic I/O first and would be advised to try turning on and off LED's before leaping into RS232. For RS232 you might want to repeat to yourself several times over that RS232 is asynchronous. The key word is asynchronous. Asynchronous means from the point of view of your code data can arrive at any time. There are only two ways to go with this.
1) Your PIC must be capable ( speed per instruction multiplied by the number of instructions)of doing its work within the time it takes a character to be transmitted to the PIC ( baud rate). This means a very short loop to get back to the next getc()
2) You use an isr tied to int_rda ..This is the preferred method since the isr can manage a circular buffer. The buffer acts like a shock absorber on a car it smooths out any bursts of incoming RS232 chars.
Receiving and sending can overlap but you have to be aware of overall I/O demands. Ex suppose you receive a char and the do a silly printf(
" My PIC just received char= %c",c) which outputs 20 plus chars for every received char then inbound chars can only be received at a throughput of less than 1/20th of the output ( in this case printf ) to avoid overruns.

arys · Joined: 09 Mar 2007 Posts: 31

thanks for the ideas. For beginning I start with very simple code. I try to send byte data from VB (which I use mscomm1.output=chr$(XX)). and received by PIC trough port B (which I set up Port B as output byte. Every bit represents different task.) here I paste the code.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

arys · Joined: 09 Mar 2007 Posts: 31

thanks. thats clear.
since getc() return character but I need the binary (ascii) number. so, i have to convert the 8bit character to 8bit integer. is it correct?
I look into sprintf(), printf() but I dont have idea how to do that. Or may be I choose wrong method.

arys · Joined: 09 Mar 2007 Posts: 31

but when i change to this code, only pinB5 ON only for 1s.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

arys · Joined: 09 Mar 2007 Posts: 31

thanks PCM. I've change to output_b(0b00000001). then its OK.