How to write 1 millisecond timer program for MC9S12ZI128 controller

baji — Tue, 09 Nov 2021 05:54:12 GMT

Hi,

We are using simulated GPIOs for one wire communication, to interface MC9S12ZI128 controller to humidity & temperature sensor (BM25S2021-1). But we are unable to read the status of sensor on GPIO pin. I think it is delay issue, please suggest whether it is correct or not. If i am wrong suggest me what is the exact problem.Here i am posting the code what i written.

void delay(u16 count) {
int i;
for(i=0;i<count;i++)
{
Nop();
}
}

void One_wire_start()
{
DDRA=0x4E;
Clear();
delay(1565);
Set();
delay(43);
}

u8 One_wire_ack(u8 *cnt)
{
u8 cnt;
DDRA=0x0E;
*cnt = _PTIA.Bits.PTIA6;
}

void Humidity(u8 *cnt)
{
u8 ow_op;
while(1)
{
One_wire_start();
One_wire_ack(cnt);
ow_op = OW_Read_Byte();
}
}

void Set()
{
PTA_PTA6 = 0x01;
}
void Clear()
{
PTA_PTA6 = 0x00;
}

char Poll_SO_OW()
{
unsigned char temp = 0;
Clear();
while (temp == 0x00) / waste time until not busy /
temp = ReadSO_OW();
Set();

}

char ReadSO_OW()
{
if (PTA & 0x1) return 1;
else return 0;
}

unsigned char OW_Get_Byte()
{
unsigned char i = 0, in = 0, temp = 0;
for (i = 0; i < 8; i++)
{
in = (in << 1); / shift 1 place to the left or shift in 0 /
temp = Poll_SO_OW(); / save input /

if (temp == 1) { / check to see if bit is high /
in = in | 0x01; / if high, make bit high /
}

}
return in;
}

unsigned char OW_Read_Byte()
{
unsigned char byte = 0;

Clear(); / enable device /
byte = OW_Get_Byte();
Set(); / disable device /
return byte; / return one byte read /
}

Re: How to write 1 millisecond timer program for MC9S12ZI128 controller

danielmartynek — Wed, 10 Nov 2021 11:04:34 GMT

Hello @baji,

This is really an application issue.

But I would scope the bus to see if a timing issue.

Also, make sure the PT6 switches between Input and Output in time.

You could use another output to signal the PT6 changes in the direction and scope it along with PTA6.

Regards,

Daniel

topic Re: How to write 1 millisecond timer program for MC9S12ZI128 controller in S12 / MagniV Microcontrollers

How to write 1 millisecond timer program for MC9S12ZI128 controller

Re: How to write 1 millisecond timer program for MC9S12ZI128 controller