HDC1080 Try

Comments

• Bean Posts: 8,129

  2018-04-30 12:57

  On the math part, you need to do multiplication BEFORE division. Otherwise you will get zero.
  
  temp_C := ((temper*165)/65536)-40)
  
  But the temper value looks way too large. 65028 will be 123.72°C ???
  
  Bean
  
• ChrisGadd Posts: 311

  2018-04-30 18:52 edited 2018-04-30 20:36

  I'm not sure if you need the configuration RST bit-15 set, as the datasheet examples never touch it, and you're shifting the returned temperature and humidity values in the wrong direction; bits [01:00] are unused, so you need to shift right by 2 to get the 14-bit value.
  
  Bean is correct that dividing a 14-bit number by 2^16 results in loss of all digits, but even with multiplying before dividing you still lose fractional digits.
  The temperature ranges from -40 to +125, a span of 165. With 14-bit resolution, each lsb equals 0.0107 degrees. The operation temper := temper >> 2 - 4000 gets you degrees x 100; 1 = -3999, 16383 = 12383.
  
  If you don't need that resolution, keep temper and humid at 16-bits and use; temper := temper * 165 / 65536 - 40 and humid := humid * 100 / 65536.
  
  If I'm reading the datasheet properly, the measurements are triggered with a write to register $00. Then after waiting for the HDC1080 to complete, the measurements are read from $00 and $01.
  A possible problem that I see here is re-addressing the register for the read begins another sample. If it's not a problem, then the i2c method readWordB can be used instead of the readByte and readNexts with shifting and or'ing. I also don't know if the readNext method even works with this device, as the HDC1080 returns 16 bits from a single register address; I've never seen that before.
  
  I included an arbitrary method for non-standard devices, to use: i2c.arbitrary(@local_long,1,@local_long,4). You'll have to declare local_long and load local_long := HDC << 1 | 1 into it before executing, the temperature will be in bits[31:18] and humidity in bits[15:02] afterward.
  
  Lastly, the PASM version of that I2C driver is intended for high speeds. The Spin version of that driver runs at about 20Kbps and uses the same methods without consuming a cog.
  
  Edited because I forgot how my own code works
• AGCB Posts: 344

  2018-04-30 20:15

  Thanks Bean & Chris
  I'll make some mods and have another go of it
• AGCB Posts: 344

  2018-05-01 11:41

  Getting closer. Thanks Chris for the ARBITRARY method!
  BUT, although the 32 bit value from the HDC keeps updating every 3 seconds as it should. everything else stays the same and the temper and humid BIN read nothing. I've tried other ways of masking but I think BITWISE AND(&) is the right way.

  PUB main |  local_long
    TV.start(0)
    WaitMS(100)
    I2C.init(SCL,SDA)
    WaitMS(100)
    
    
    I2C.writeWordB(HDC,Config_reg,Config_params)   'configure device
    WaitMS(100)
      humid~
      temper~
    
    
     repeat
       local_long := HDC << 1 | 1
       I2C.command(HDC,$00)   'start a temp, hum measurement
        WaitMS(100)                 'allow time for measurement
       temper:=humid:=0
      
       tv.home
       i2c.arbitrary(@local_long,1,@local_long,4)
       WaitMS(100)
       tv.str(string("32 bit output from HDC"))
       tv.cr
       tv.bin(local_long,32)
       tv.cr
       WaitMS(100)
       
       temper:= @local_long & %1111_1111_1111_1111_0000_0000_0000_0000  'AND to mask all except 31:18
       
       tv.cr
       tv.str(string("Temp in decimal  "))
       tv.dec(temper)
       tv.cr
      
       tv.str(string ("temp in bin = "))
       tv.bin(temper,14)
       
       tv.cr
       tv.cr
       tv.str(string("hum in bin = "))
       tv.bin(humid,14)
       humid:=@local_long & %0000_0000_0000_0000_1111_1111_1111_1111 'AND to mask all except 15:02
       tv.cr
       tv.str(string("Hum in decimal  "))
       tv.dec(humid)
       waitms(1000)
  
       temp_C := ((temper*165/65536)-40)
       RH:=(humid*100/65536)
       tv.cr
       tv.cr
       tv.str(string("temp in c = "))     
       tv.dec(temp_c)
       tv.cr
       tv.str(string("RH = "))
       tv.dec(RH)
       WaitMS(3000) 
  

  

  

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• macrobeak Posts: 358

  2018-05-01 13:26

  Hey AGCB did you get the code for the BME280 to work successfully?
• ChrisGadd Posts: 311

  2018-05-01 17:05

  You are correctly using the immediate value of local_long when you display the binary value, but are using the address of local_long when applying the masks.
  I tried converting the returned binary value into temp and humidity and discovered another problem in that the i2c.arbitrary method reads little-endian.
  The easiest/laziest fix is:

  tempC := local_long.byte[0] << 8 | local_long.byte[1]
  tempC := tempC * 165 / 65536 - 40
  
  RH := local_long.byte[2] << 8 | local_long.byte[3]
  RH := RH * 100 / 65536
  

  Looks like it's about 19c and 43% RH there.
• AGCB Posts: 344

  2018-05-24 09:25

  Chris
  For some reason I didn't see your reply. I've been busy and not programming.
  
  That took care of the problem and it now works. I get mixed up with that @ operator. Still no handle on it.
  
  I'll try to clean up the code and add it to my weather station.
  
  Thanks very much Chris!
  Aaron
• AGCB Posts: 344

  2018-06-13 09:08

  ChrisGadd wrote: »

  I tried converting the returned binary value into temp and humidity and discovered another problem in that the i2c.arbitrary method reads little-endian.

  
  
  Chris
  
  Could not the value just be reversed with >< to get big-endian? I'm less than novice!
  
  Aaron