The readings seem wrong. I get only constant value displayed. The arrow in the middle of the display is not blinking. I tried powering the board with my JTAG debugger using the on-board JTAG connector and I also tried powering the board from external 3.3V power supply using the UEXT pins. Tried different positions of jumpers and BAT/UEXT switch. What is wrong? Why the readings stay constant?
The source of the problem is the power supply. MOD-EKG is a sensitive board and glitches or noises power supply lines might affect the readings. Even if the USB ports and the power supply unit are of good quality, there is still parasitic capacitance between the human body and mains power line, which affects the readings. Be sure to test with a 3V battery - either insert a good CR2302 coin battery directly in the connector at the back of MOD-EKG or attach a 3V battery to pins #1 and #2 of the UEXT (2 batteries x 1.5V also do the job). If you wish to power the board from the JTAG or external power supply make sure there is galvanic isolation or good filtering between the power supply and the MOD-EKG board. For example, if you want to isolate your JTAG debugger from the mains power hum you can use our USB-ISO product (between the computer's USB port and the JTAG debugger).
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