We have found a case in which we are consistently reading erroneous values from the TMP275 sensor.
At every “sample” our product performs the following sequence (t is time):
1) t=0, power on the TMP275
2) t=44ms, set the converter resolution (R1/R0) to 11-bits
3) t=194ms, read the temperature register
The sequence above occurs once every 3 seconds. In between samples the system is powered down and the voltage slowly decays. In fact, the voltage to the TMP275 is ~0.625V when power is applied at the start of the next sample. If we wait longer between samples (60-seconds), the voltage is much lower and the problem does not occur. Also if we add a 40ms delay before or after step #2 in the sequence above, the problem does not occur at the 3-second update rate.
We are trying to implement a fix or workaround. The 40ms delay seems to work but since I don’t completely understand the problem I don’t feel comfortable in this fix.
Can you help explain why this problem occurs?
Hi,
Similar problem with me. Have you any solution for this yet ?
Of the 2 bytes I read from temp reg, one of the value (second byte or LSB byte) is always FF.
In your case, hope you are not hitting time out, when you wait longer (>54ms), after initiating a slave address send.
AC
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