Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

we are facing an issue with one-wire communication by using DS2485

Status
Not open for further replies.

sumitthorat0909

New Member
we are facing an issue with one-wire communication by using DS2485,
We not getting correct data while communicating.

I followed the command sequence as per the datasheet after matching the ROM id by using command 55h .
I do not get any data while trying to read the next block by using the command (66H). I did delay calculation as per the data sheet.
It’s always returning scratchpad data only.
Also refer bellows debug log :
Device: 1 1A00000004959C42: 55 42 9C 95 04 00 00 00 1A
Ttx_buff : AB 0A 07 55 42 9C 95 04 00 00 00 1A//Match ROM
Trx_buff : 0A AA 55 42 9C 95 04 00 00 00 1A FF
Ttx_buff : AB 0B 07 66 FF FF FF FF FF FF FF FF FF//Read scratch Pad
Trx_buff : 0B AA 66 FF FF FF FF FF FF FF FF FF FF
Scratchpad: [66 FF FF FF FF FF FF FF FF FF ]

- tF: -196
Temperature: -196 [F], -127 [C]
Can you suggest what I need to do to resolve this issue .
Code:
code :
if (DS2485_OWNext())
{
if (*romPtr == OW_FAMILY_DS28EA00)
{
#define SP_TEMP_LSB_INDEX (1)
#define SP_TEMP_MSB_INDEX (2)

int tC = 0;
int tF = 0;
int tVal = 0;

// Print device found.
for (i = 7; i >= 0; i--)
{
printf("%02X", *(romPtr + i));
}

printf(": ");

// Device already selected from search
// send the convert command.
if (!OWWriteBytePower_Ds2485(0x44))
{
printf("Fail convert command\n");
return(FALSE);
}

// Delay for 1 second.
msDelay(1000);

// Turn off the 1-Wire Net strong pull-up.
config_reg=0;
// default configuration
m_c1WS = 0;
m_cSPU = 0;
m_cPPM = 0;
m_cAPU = ACONFIG_APU;
config_val[1]=m_c1WS | m_cSPU | m_cPPM | m_cAPU;
// write the default configuration setup
if (!DS2485_write_config(config_reg,config_val))
{
printf("DS2485_write_config() failed.\n");
return(FALSE);
}

// Verify complete.
if (OWReadByte_Ds2485() != 0xFF)
{
printf("ERROR, temperature conversion was not complete\n");
return(FALSE);
}

// Select the device.
sendpacket[0] = 0x55; // Match command.

for (i = 0; i < 8; i++)
{
sendpacket[i+1] = *(romPtr + i);
}
if(DS2485_OWReset())
{
// MATCH ROM sequence.
OWBlock_Ds2485(sendpacket,9);

// Read Scratch pad.
sendlen = 0;
sendpacket[sendlen++] = 0x66;

for (i = 0; i < 9; i++)
{
sendpacket[sendlen++] = 0xFF;
}

OWBlock_Ds2485(sendpacket,sendlen);
//DS2485_Data(romPtr,sendpacket);
tVal = (sendpacket[SP_TEMP_MSB_INDEX] & 0x07) << 8;
tVal += sendpacket[SP_TEMP_LSB_INDEX];
//tVal = ((sendpacket[SP_TEMP_LSB_INDEX] << 8) | sendpacket[SP_TEMP_MSB_INDEX])/65536;
//tVal = -45 + (175 * tVal);
//printf("\nCalculated Temperature: %d C\n", tVal);
/* Celsius.
*****/
tC = tVal;
tC /= 16;

if ((sendpacket[SP_TEMP_MSB_INDEX] & 0xf8))
{
tC *= -1;
}

/* Fahrenheit.
*****/
tF = ((tC * 9) / 5) + 32;
printf(" - Temperature: %i [F], %i [C]\n", tF, tC);
}
else
{
printf("NO RESET\n");
return(FALSE);
}
}
}
OW block code :
int OWBlock_Ds2485(unsigned char* tran_buf, unsigned int tran_len)
{
int status = TRUE;
unsigned char Trx_buff[tran_len+3];
unsigned int TxRx_len=tran_len+1;
int i = 0;
//Timing Parameter as per Ds2485 Datasheet
unsigned int t_w0l=68;
unsigned int t_rec=6;
unsigned int t_rstl=560;
unsigned int t_rsth=560;
unsigned int tOP=40;
unsigned int tSEQ=20;

// delay calculation as per the 1W Block length
unsigned int t_slot = t_w0l + t_rec;
unsigned int ow_rst_time = t_rstl + t_rsth;
unsigned int one_wire_time = ((t_slot * 8) * (tran_len)) + ow_rst_time;
unsigned int delay = tOP + (tSEQ*(tran_len + 1)) + one_wire_time+1000;

Trx_buff[0]=ACMD_1WBRW; // 1W Block Read Write Command
Trx_buff[1]=TxRx_len; // 1W Block length
Trx_buff[2]=0x07; // 1W Block configuration Parameter OW_RST=1,IGNORE=1,SPU=1

#if defined(OW_VERBOSE_DEBUG)
printf("%s(): Enter, tran_len: %i.\n", __func__, tran_len);
#endif
memcpy(&Trx_buff[3], (void *)tran_buf, tran_len);
status = I2cWrite(Trx_buff, sizeof(Trx_buff),DS2485_DEVICE_ADDRESS);
if (status == FALSE)
{
printf("%s: Failed to Write OWBlock", __func__);
}
else
{
udelay(delay);
status = I2cRead(Trx_buff, sizeof(Trx_buff),DS2485_DEVICE_ADDRESS);
if(status)
{
if(Trx_buff[0]== TxRx_len && Trx_buff[1]==0xAA)
{
memcpy(tran_buf,&Trx_buff[2],tran_len);
}
else
{
printf("%s: Failed to Read OWBlock", __func__);
return 0;
}
}
else
{
printf("%s: Failed to I2C Read OWBlock", __func__);
return 0;
}

}
return tran_len;
}
 
Last edited:
Just for future reference, when you post code use the code tags, preserves tabs and indent,
so code more readable.

1656418131929.png



Regarding signaling you see proper rise/fall times on the buss as well as logic levels ?


Regards, Dana.
 
- tF: -196
Temperature: -196 [F], -127 [C]
Does that mean that you are operating this thing at -127DegC ??

The DS2485 datasheet clearly states:
1656423555135.png


If my understanding is correct, you may be running this thing a little bit too cold.

JimB
 
Does that mean that you are operating this thing at -127DegC ??

The DS2485 datasheet clearly states:
View attachment 137639

If my understanding is correct, you may be running this thing a little bit too cold.

JimB
No Jim I got the wrong value on one wire. value is -127 because there is some calculation to convert data to proper formate . when I try to receive data I got the wrong data and the calculation also goes wrong.
 
Status
Not open for further replies.

New Articles From Microcontroller Tips

Back
Top