how to write c code for motor

main()
{
motor_on();
}

This could work. Depends on how motor_on() is implemented.

O.k., that was the fun part. You have to supply a lot more information on your project:
- What kind of controller do you use?
- What kind of motor do you use?
- How is the motor attached to the controller?
- Do you have any libraries for motor control you might use?

Harald

 

jackorocko is right.
My personal opinion: Programming in embedded C is structurally not too different from programming in C on a PC. The BIG differences are:
- in the embedded world your ressources are very limited (little memory, slow CPU, mostly no floating point unit, little mass memory etc.). Mind that this is a very general statement. I know very well that there are embedded CPUs with floating point and even with lots of memory etc.
- in the embedded world you have direct access to a lot of low level periphery. For example you can read a single input pin of the CPU or you can set a single output pin of the CPU. Both possible in the PC world only with lots of effort.
- in the embedded world you often have to deal with real-time requirement´s, menaing that you may have to guarantee a rsponse of the CPU to an input event within a limited (and mostly well defined´) time frame.

So if you want to control a motor, before you start writing your first line of code you need to know:
- How is the motor connected to the CPU?
- Which pins of the CPU (or maybe a peripheral chip) control the motor? What logic levels are required for "forward"?
- How is the program informed to start and stop the motor (pushbuttons? other events?)

For starters you may have a look at the arduino platform (which doesn't mean that jackorocko's suggestion of a PIC is not a good idea). The arduino comes with lots of libraries and so called "shields" for different I/O purposes. Unfortunately that's about all i know about the arduino.

Harald

 

I'm not versed in PIC programming. However, there should be a command simiar to
PORTB = <value>;
where <value> is an 8 bit data that defines the states of the port bits B0..B7.
For example:
PORTB= 0x01;
will set B0 = high, B1...B7 = Low

This seems easy, but beware: there is a pitfall here: The command as written above will set all port bits to low or high according to the bit pattern of <value>, disregarding your intent that you probably may want to set a single port bit only. To achieve this, you have to first read the current state of the port bits, change the one bit you want to be set or reset and write the modified port bits.
To set a single bit you use the OR function, ORing the bit pattern of the port with a bit maskt that sets the single bit you want to change, but leaves the rest unchanged:
TMP = PORTA; /* read port bits */
TMP = TMP | 0x01; /* set bit 0 to 1, note: unchanged bits are 0 in the bit mask*/
PORTA = TMP; /* write new port bits */
To reset a single bit you use the AND function. ANDing the bit pattern of the port with a bit mask that resets the single bit you want to change, but leaves the rest unchanged:
TMP = PORTA; /* read port bits */
TMP = AND | 0xFE; /* reset bit 0 to 0, note: unchanged bits are 1 in the bit mask*/
PORTA = TMP; /* write new port bits */

You have to know which port pins your motor is attached to and what logic levels are required to start and stop the motor.

Harald

 

You're not supposed to "set sensor low or high". The sensor is an input and should be read by a statement like
Sensor = PORTA & 0x08 /hex 08 = 0000 1000 -> only bit A4 is relevant, all other bits in "Sensor" are set to 0.
Similarly setting port pins on PORTB follows the scheme I wrote in my previous answer. Please re-read.

About Hex-Code you can read up here: http://www.theproblemsite.com/codes/hex.asp

May I suggest you first get some experience with writing C code at all before you tackle embedded programming? To me it looks like your fighting at two fronts at the same time. Get a grip on C-programming first, then apply your knowledge to embedded programming and learn the specifics.

Otherwise you may have a look at this course: http://www.swarthmore.edu/NatSci/echeeve1/Ref/C for PIC/C_Intro.html

Harald

 

From
#include<pic.h>
I assumed vead is using a PIC microcontroller. The DDRA and PORTA statements, on the other hand, look a lot like AVR.

I like that binary notion 0b00001000 instead of 0x08 because in this case it is a much more obvious solution for representing the bit mask. I didn't know that this notion is available in C (I use 0x notation all the time).

Since the motors are connected to 2 port pins each, both port pins need to be set and reset, not just one. Depending on the exact circuit, which vead hasn't disclosed to us yet, this could look like:

void motor_1_forward()
{
int temp;

temp = PORTB;
temp = temp & 0b11110111; /* B3 = 0 */
temp = temp | 0b00100000; /* B5 = 1 */
PORTB = temp;
}
void motor_1_backward()
{
int temp;

temp = PORTB;
temp = temp | 0b00001000; /* B3 = 1 */
temp = temp & 0b11011111; /* B5 = 0 */
PORTB = temp;
}
void motor_1_stop()
{
int temp;

temp = PORTB;
temp = temp | 0b00101000; /* B3 = B5 = 1 -> same logic level on both pins means no voltage differential on motor */
PORTB = temp;
}

Thes eroutines can be modified accordingly using other port pins for motor 2. From within the main program it is sufficient to call these routines.

By the way: It is good coding styöe to "hide" the binary representations by using #define statements for the preprocessor. This also eases maintenance. If, for example, you connect the motor(s) to other pins you just redefine the bit pattern in the #define statement.

Harald

 

I told you before: PORTA is an input, so the statement
PORTA=0b00001000; // set as high pin
doesn't make sense. You can read from PORTA, but not write to it.

And nobody can tell you whether tis staement
(port B=0b00111100); // both motor move forward
works unless you post the schematic circuit how the motor is attached to the port pins.

Harald

Harald

 

It may do something though. It could tun on the pull-up resistors for that single input.

But yeah, it certainly won't set a high value to an input (because that's kind of a meaningless assertion)

 

What I completely miss in the C-code presented is the inizialization of the AVR.
You need to:
- initialize the stack pointer
- initialize the clock system (whick clock: internal / external, which frequency etc.)
- initialize an other function blocks

Maybe you just left this out of the code you showed us to keep it short. But it is required, See here http://www.jarkonkotisivu.org/AVRcoder/ for a little tool to assist in generating the necessayr settings (and it even generates C-code!).

By the way, here http://iamsuhasm.wordpress.com/tutsproj/avr-gcc-tutorial/ is a tutorial on writing C-Code for the AVR controllers.

Harald