Use Renesas MCU and MCP96RL00 to realize temperature acquisition of various thermocouples. Supports a total of eight types of thermocouples from KJTNSEBR.
        The reason for doing this is that the heating core of the electric soldering iron that I have been using for a long time has broken. After replacing it with a new heating core, I always feel that the temperature is not accurate. I happened to buy a piece of MCP96RL00 thermocouple temperature acquisition chip from the overseas shopping event of Lichuang Mall. This Renesas RA MCU & Lichuang EDA training camp is not limited to the type of work, so we used Renesas R7FA2E1A72DFL and MCP96RL00 to make a thermocouple thermometer to calibrate the temperature of the soldering iron, and of course to measure other things such as oil temperature and gas. The stove temperature and the like are no problem either.

hardware

        MCP96RL00 is similar to Maxim's MAX31855 and MAX6675, communicating with the MCU through the I2C bus. The following is the introduction from the official document (machine translation):

        The schematic diagram is as follows. You only need to add a decoupling capacitor and a terminal block to connect the thermocouple.

        Since there is no complicated text to be displayed, the digital tube is used directly, which is clearer and more intuitive. The digital tube uses a four-bit common cathode digital tube, and the pins of R7FA2E1A72DFL are relatively abundant, so the MCU push-pull output is directly used to drive the scanning display, and the maximum current is less than 20ma.

        TYPE-C female socket and power indicator light, this MCU supports 5V voltage which is very convenient and does not require LDO. The two 5.1K pull-down resistors are used to identify the C TO C line. If not used, they do not need to be soldered.

        Four buttons, sw1 and sw2 are used to adjust the thermocouple type. The other two keys are reset and boot, which are needed for serial port downloading.

        Serial port download, direct pin header.

        MCU schematic diagram. Since a very accurate clock is not required, an external crystal oscillator is not needed. The ADC/DAC is not used either, the AVCC pin is directly connected to 5V.

        PCB diagram (copper layout has been hidden), there is basically nothing to pay attention to in the wiring, it is all low-speed signals.

software

        The code is written in keil, and the initialization code is automatically generated using RASC.

        Please see the attachment for details of the software part. The comments are more detailed. Here is a section of the main function:

Physical display

        Thermocouples can be bought as finished products, or you can buy an extension wire that costs one or two yuan and twist the two wires together. There is basically no difference in the actual measured temperature, because the composition of the extension wire is the same as that of the thermocouple. If you use a spot welder to weld them together, Better.

Physical map:

Measuring soldering iron tip temperature:

How to verify the accuracy of this temperature? Use a multimeter to measure the voltage across the thermocouple at the millivolt level:

At this time, the ambient temperature is about 25 degrees, and the thermocouple type is E. Then use the lookup table method to calculate the temperature at this time:

22.3+1.495≈23.8, which corresponds to about 335 degrees, and the accuracy is okay.

Press SW1 to enter the thermocouple type switching interface, press SW2 to switch types, and then press SW1 to confirm.