Going back to electronic after a 20 years break

Diode mode on a voltmeter is great to test ...... diodes The main problem is that voltmeters don't get very high in terms of forward/reverse voltage. Some struggle with voltage higher than ~ 2.5 V, which is not enough for Zeners / Blue Led So i wanted a cheap, simple, usb powered diode tester. Let's see what was done The circuit is made of the following main parts : * 1/2 LM358 :A constant current circuit, the average value is 5 mA. It can be set using the pot. It means the LM358 is enough to deliver such current without a mosfet driver. * 1/2 LM358 : A differential amplifier to get the tension from the diode to test * A boost DC/DC converter, to raise the 5v input to 20 V * One ebay 1$ voltmeter And it works fine up to ~ 17v. The only issue is that the cheap voltmeter is not very accurate. I  have  tuned it to be accurate around 3v, the further away you get, the larger the error. But that's good enough for colored leds an low value zeners, which is 90% of my

You can revert to Jyetech firmware easily, assuming you have a STLink v2 and soldered the SWD connector 1- Download the firmware from jyetech, unzip it 2- Power the board through the SWD connector and DONT SWITCH IT ON NEVER POWER BOTH VIA SWD AND VIA THE BOARD AT THE SAME TIME 3- st-flash --format ihex write 113-15001-064.hex since we dont touch at all the content of the eeprom chip, you shouldnt have issue with the serial number ( untested).