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TCN75A One shot mode help

 
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jspencer



Joined: 22 Dec 2003
Posts: 57
Location: Boise, ID USA

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TCN75A One shot mode help
PostPosted: Wed Mar 08, 2006 8:32 pm     Reply with quote
I don't think that I am doing this correctly, so if someone can offer a little advice. I'm not exactly sure if I'm doing the one shot mode for the TCN75A correctly. Here is what I am doing currently. It works, but it is causing some issues with my external eeprom. I think that I am leaving it in a bad state or not finishing the transmission.

Code:
   

// TCN75 i2c addresses
#define TCN75_I2C_WRITE_ADDR  0x90
#define TCN75_I2C_READ_ADDR   0x91

// TCN75 register addresses
#define TCN75_TEMP_REG_ADDR    0x00
#define TCN75_CONFIG_REG_ADDR  0x01
#define TCN75_THYST_REG_ADDR   0x02
#define TCN75_TSET_REG_ADDR    0x03

#define TCN75_SHUTDOWN_MODE    0x01
#define TCN75_ONE_SHOT_MODE    0x81
#define TCN75_CONTINUOUS_MODE  0x00

// put in shutdown mode so that we can access one shot mode.

   i2c_start();
   i2c_write(TCN75_I2C_WRITE_ADDR);
   i2c_write(TCN75_CONFIG_REG_ADDR);
   i2c_write(TCN75_SHUTDOWN_MODE);
   i2c_stop();

// now access one shot mode and read the temperature

   i2c_start();
   i2c_write(TCN75_I2C_WRITE_ADDR);
   i2c_write(TCN75_CONFIG_REG_ADDR);
   i2c_write(TCN75_ONE_SHOT_MODE);

   i2c_start();
   i2c_write(TCN75_I2C_WRITE_ADDR);
   i2c_write(TCN75_TEMP_REG_ADDR);
   i2c_start();   
   i2c_write(TCN75_I2C_READ_ADDR);
   msb = i2c_read();
   lsb = i2c_read(0);
   i2c_stop();



Appreciate the extra set of eyes.

jspencer
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Mar 08, 2006 9:34 pm     Reply with quote
You're missing the stop bit after the config write. Add the line
shown in bold below:
Quote:
i2c_start();
i2c_write(TCN75_I2C_WRITE_ADDR);
i2c_write(TCN75_CONFIG_REG_ADDR);
i2c_write(TCN75_ONE_SHOT_MODE);
i2c_stop(); // Add this line

i2c_start();
i2c_write(TCN75_I2C_WRITE_ADDR);
i2c_write(TCN75_TEMP_REG_ADDR);
i2c_start();
i2c_write(TCN75_I2C_READ_ADDR);
msb = i2c_read();
lsb = i2c_read(0);
i2c_stop();
jspencer



Joined: 22 Dec 2003
Posts: 57
Location: Boise, ID USA

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PostPosted: Thu Mar 09, 2006 9:40 am     Reply with quote
Thanks for the extra set of eyes PCM.

jspencer
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