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There is a short ECG file named "sample.hlr" that is installed with the application.

Dear MiguelDP, The PCB is not mandatory to build the hardware because there are not so many wires. It seems some SD boards are poor (see nhc14 comment on ECG Logger page). There are also SD Cards that are not very good (too much consumption). Maybe you have already fixed the problem otherwise could you tell me more about the issue ?

Read the Help file Device (Holter) > Device Error codes. ERR2 createContiguous function failed There is an issue with your SD Card or SD Card reader module ERR0 SD card failed! Check SD board and card, reformat SD card ERR1 Cannot rename a temporary file Extract the SD and delete the data__.(hlr/txt) file(s). Clear all files (CLEAR), reformat SD card ERR2 createContiguous function failed ERR3 contiguousRange function failed ERR4 cacheClear function failed ERR5 file erase failed ERR6 writeBegin function...

New v3 application and firmware can run on old hardware with limitations. Upgrade the old hardware to v3.

Latest 3.1.2 version is able to support correct signal's polarity for V1 to V6 (in alpha test).

Dear Carlos, Keep in mind that we use an Arduino Nano for this project with only 30KB of memory for the code. The problem you encountered is due to the wiring of the cable probably and can be solved by using the correct electrodes or placement not matching the electrode's colors. Please refer in the PDF documentation to the "Electrode's inversion" section where I show the different electrode's combinations and their related ECG diagrams to correct this issue. I hope this will solve your problem.

Read the Help file Device (Holter) > Device Error codes. ERR2 createContiguous function failed There is an issue with your SD Card or SD Card reader module

Clearly the signal goes to zero randomly. As far as I know, this problem has not been reported by other users. Therefore this could be due to a poor connection between the Cardio breadboard and the Arduino ADC. Also check if the AD8232 shutdown signal is HIGH (3V3) in normal operation (if not, adjust the resistors). This is probably not due to a lead disconnection because the ECG signal is stable neither due to a problem with the SDC because the pause does not match a block of 512 bytes. Hope this...