Hi everybody.
I've got a problem using Dallas DS18s20 temperature sensor. In particular, it seems to me it sends a wrong crc.
Here's how I use it. Firstly, I perform a temperature conversion, and a second later I read data stored in its scratchpad. Data regarding temperature and fixed values seems correct (temperature is correct, the other parameters are always the same), but the crc is wrong.
What can I do to solve the problem?
Thanks,
Max
Max,
How are you determining that the CRC is incorrect? Is it possible that the bus master is incorrectly calculating what the CRC should be?
Hard to say much else without more information. What hardware are you using (microcontroller/microprocessor), how are you calculating CRC, etc? There is apretty good writeup in the datasheet and Dallas (now Maxim) application note AN27 covers CRC quite thoroughly.
Good luck, Richard
I see, I didn't give you a lot of informations.
My micro reads correctly data from the bus, I've verified it using an oscilloscope.
The micro also calculates the CRC correclty, I've verified it using an online crc calculator.
Another trial for that is I always receive default data from DS18s20 correctly.
I have no idea about how to solve this bug...
Max
Another thing I noticed is this one. For some couples (temperature, counts remaining) I always receive a wrong CRC, while when "counts remaining" is one unit less, the crc is correct. For example
Temperature - LSB = 0xA3 Temperature - MSB = 0x01 TH = 0x4B TL = 0x46 configuration register = 0x7F reserved = 0xFF counts remaining = 0x0D
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