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License: GNU General Public License v3.0
Read thermocouple temperature using a MAX31855 converter
License: GNU General Public License v3.0
This code nicely provides a fault code to help with troubleshooting, but the wiki didn't mention my issue: Fault code 7. I now realise this must be fault codes 1, 2 & 4 combined. It might be helpful to present the codes as they are received, 3 separate binary digits presenting different issues.
From the data sheet: Bits D0, D1, and D2 of the output data are normally low.
Bit D2 goes high to indicate a thermocouple short to VCC
Bit D1 goes high to indicate a thermocouple short to GND
Bit D0 goes high to indicate a thermocouple open circuit.
Let's put Fault code 7 aside, it means nothing was correct. What I've discovered is the breakout board I'm using actually has a track between T- and GND, which presents as fault code 2. If I remove the thermocouple I see fault code 3 because faults 1 and 2 are active.
It seems clear the breakout board is garbage and only redeemable by cutting that track if I can get a scalpel into it. However...
The datasheet also suggests T- is tied to ground when measuring the thermocouple, so why is it considered a fault condition? I'm wondering if the board should work if I ignore errors (it doesn't), or if there's an error in the datasheet.
"When executing the temperature conversion of the external thermocouple, the connections to the internal fault-detection circuit are opened (switches S1 and S2 in the Block Diagram) and the switch connecting the coldjunction compensation circuit is opened (switch S5). The internal ground reference connection (switch S3) and the connection to the ADC (switch S4) are closed. This
allows the ADC to process the voltage detected across the T+ and T- terminals."
and later: "The fault-detection circuit tests for shorted connections to VCC or GND on the T+ and T- inputs".
I cut the track and resolved the fault condition, now I just get nonsense data. Internal temp 128 (or -128) and probe -1100 sitting on my desk. Probe goes to -2048 in ice water and +1000 when I warm it again with my hand. It's possible the chip was binned as faulty in the first place. I've got 25 more to test.
Describe what the feature request is and if it solves an issue or adds functionality
Question asked by @billpurta Currently the library supports only one MAX31855 device although several may be present
Describe the solution you'd like
A such support or describe how it can be done with the current library
Describe alternatives you've considered
N/A
Additional context
N/A
Infrequent and non-deterministic erroneous readings from the temperature probe.
There is a typo in the demo. SO the compiler crashes
see above
Copy the demo and run it.
Explain what needs to be done in order to reproduce the problem.
while (!MAX31855.begin(SPI_CHIP_SELECT,SPI_MISO,SPI_SYSTSEM_CLOCK)) // Software SPI for MAX31855
The tyope is in the SPI_SYSTSEM_CLOCK), which shoud be SPI_SYSTEM_CLOCK)
I tried the demo, and it passes initialization even with no device connected on an arduino mega. It then reports no faults, and reads 0.0C temperatures for ambient and thermocouple.
Does the library supports multiple PMODTC1 Readings into Arduino UNO?
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