Right,
sorry about that.
I'm working on PIC18F4550.
Compilable function ... well I can give you the defs and a code
snippet:
typedef struct {
union {
uint16_t nco;
struct {
unsigned nco_low_bits :15;
unsigned nco_hi_bit :1;
};
};
struct {
unsigned has_next :1;
unsigned reserve_b1;
unsigned reserve_b2 :1;
unsigned reserve_b3 :1;
unsigned reserve_b4 :1;
unsigned reserve_b5 :1;
unsigned reserve_b6 :1;
unsigned reserve_b7 :1;
};
uint16_t speed;
uint8_t next_steps;
uint16_t next_speed;
uint8_t next_dir;
uint8_t steps;
} motor_t;
#define MOTOR g.motor[0]
and the code snippet:
....
MOTOR.nco += MOTOR.speed;
if (MOTOR.steps) {
if (MOTOR.nco_hi_bit) { // speed NCO overflowed and we have steps left =>
generate pulse
MOTOR.steps--;
....
so basically it is just advancing a 16 bit unsigned variable
by adding an other 16 bit unsigned to it. I treat the value
as 15 bit and check the highest bit for overflow, in assembler
I would have access to the carry bit and could use the full
16 bits which would better but I'm a happy to use just 15 bits
if I can stay in the C-domain.
Sorry that I did not provide this info in the first place,
I was so deeply into my code that I took all this granted,
which it isn't of course.
br Kusti
On 24/06/2014 20:40, "Philipp Klaus Krause" <p...@spth.de> wrote:
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>I think it would be helpful to readers of your post, if you'd
>
>* State which target this is about
>* State which data types the variables are (or even better: give a
>compileable function)
>
>While these could be inferred from the assembly code you posted, they
>would still make reading easier.
>
>Philipp
>
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