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RTD Temp Sensor Amplifier help
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RTD Temp Sensor Amplifier help

by wleibe on Fri Feb 15, 2019 9:44 am

Hello! I purchased a MAX31865 temp sensor amplifier for my 3 wire RTD temp probe. I made the required changes to the amplifier. (Two jumper connections and one trace cut.) Connected the sensor to my Ardunio UNO SPI bus with CS 1 instead of 10. However, I can't seem to get the MISO pin to toggle. (I have an old Techtronix scope that I am using so I can see the bus, but it is an analog scope without memory.) I can see the CLK, CS, and MOSI pins move, but the SO is just dead. As I'm using an UNO my voltages are 5V. I've confirmed that the 3.3 volt output is working on the daughter card.

Can I get some advice on what I can check on the daughter card to see what is wrong?


BTW I'm using the Adafruit example code with one change for the CS from 10 to 1.

Thanks!
Wendel

wleibe
 
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Re: RTD Temp Sensor Amplifier help

by adafruit_support_bill on Fri Feb 15, 2019 9:59 am

Ardunio UNO SPI bus with CS 1 instead of 10.

Is there any serial communication in your test program? Pins 0 and 1 on an UNO are the serial port.

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Re: RTD Temp Sensor Amplifier help

by wleibe on Fri Feb 15, 2019 10:28 am

Well, I'm using the test app which uses the USB serial port. Are they tied together? Otherwise I'm using the example app as a test. (Mine won't work either so I went backwards and loaded the adafruit app.) My app uses the USB serial port as well for communications.

Wendel

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Re: RTD Temp Sensor Amplifier help

by adafruit_support_bill on Fri Feb 15, 2019 11:27 am

Pins 0 and 1 are the hardware serial pins for the Atmega328 microcontroller. These are connected to the 16U2 USB/Serial chip. So using pins 0 or 1 is problematic on an UNO if you are doing serial communication.

Other processors like the 32U4, the M0 and M4 have native usb/serial capability, so their pins 0 and 1 are free for general use.

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Re: RTD Temp Sensor Amplifier help

by wleibe on Fri Feb 15, 2019 11:46 am

OK, I've pulled it apart and I'll give CS 10 a try instead of 1.

Thanks,
Wendel

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Re: RTD Temp Sensor Amplifier help

by wleibe on Fri Feb 15, 2019 11:54 am

Excellent. That did it.

THANK YOU!

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Re: RTD Temp Sensor Amplifier help

by adafruit_support_bill on Fri Feb 15, 2019 11:57 am

Good to hear! Thanks for the update.

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Please be positive and constructive with your questions and comments.