Is it possible using Tmex only to read the humidity on the humidity\temp\solar unit.
I have succeded in reading hte temp on the 1820 using tmex, and have problems reading the humidity on the ds2438.
Perhaps it is a timing issue but I can't figure out in tmex what would be used for skip rom (CCh). I can read the scratch memeory but do not seem to be populating it.
If someone has a routine which runs through the temp, humidity and solar in TMex I would love to see the code.
I am using Labview, but could use Java.
Thanks
I don't have a humidity sensor, but this operates similar to the DS2450 and most other 1wire chips that take time to collect data, even the temp sensor. The simple way to do it is select the chip (TMRom, TMStrongAccess), send a command (TMTouchByte), wait for conversion to be completed.
In this case you need to send a Convert V
Convert V [B4h]
This command instructs the DS2438 to initiate a voltage analog-to-digital conversion cycle. This sets the
ADB flag (see Status/Configuration register discussion in the Memory Map section). The voltage supply
that is measured is defined by the AD bit of the Status/Configuration register. When the A/D conversion
is done, the ADB flag is cleared and the current voltage value is placed in the VOLTAGE REGISTER of
page 00h. While an A/D conversion is taking place, all other memory functions are still available for use.
If the bus master issues read time slots following this command, the DS2438 will output “0” on the bus as
long as it is busy making a voltage measurement; it will return a “1” when the conversion is complete.
The humidity sensor is hooked to the DS2438 VAD. You'll need to set the AD bit, page 0, byte 0.
The default is 1, read VDD, and that's not what you want. You'll need to set that bit to 0.
AD = Voltage A/D Input Select Bit. “1” = the battery input (VDD) is selected as the input for the
DS2438 voltage A/D converter; “0” = the general purpose A/D input (VAD) is selected as the voltage
A/D input. For either setting, a Convert V command will initialize a voltage A/D conversion. The default
value of this bit is a “1” (VDD is the input to the A/D converter).
Skip rom is tmtouchbyte(0x55).
I always select a specific chip by the 64bit code using tmrom,tmstrongaccess (match rom)
