NEXTION 16 Keys Matrix Keypad 4x4 Membrane Keyboard Module Array Switch for Arduino

Was skeptical because of the weird reviews. This is just a standard rows and columns matrix. I used Arduino keypad library and had it running in 5 mins. Install library, open the Custom Keypad sketch. See what pins to connect where. I changed two of my rows from 0 and 1 (default in the library) to 8 and 9 so it wouldn't interfere with serial communications. So mine looks like this:byte rowPins[ROWS] = {3, 2, 8, 9}; // Skip the first solder pad so solder pads 2, 3, 4, and 5 connect to digital in 3, 2, 8 and 9byte colPins[COLS] = {7, 6, 5, 4}; These connect to pads 6,7,8 and 9. Ignore the 10th pad .THEN adjust the sample code to THIS keyboard's layout:char hexaKeys[ROWS][COLS] = { {'1','2','3','A'}, {'4','5','6','B'}, {'7','8','9','C'}, {'*','0','#','D'}};Upload the sketch, open your serial monitor, making sure it is set to 9600 baud. And voila. Easy peasy.Nice looking keypad for cheap.

the contacts inside are giving resistive connections some as high as 680 Ohms. varies from row to row and column to column. not sure if this is due to material of contactor or if it is due to contamination on the board but it can cause issues when trying to use this with Arduino boards. definitely not a quality product.UPDATE 6/19/19: the problem is that they used resistive paint to bridge over from point to point instead of going to a double sided board. this causes a resistive connection on those pins that are connected in this manner. it also causes a resistive connection to some of the traces that are bridged and makes a mess of the matrix. I had to go in and carefully scratch off the resistive paint in places and then very carefully remake the connections using 30 gauge wire. haven't finished it yet but it should work. getting rid of the paint is the hard part. Otherwise this thing is just useless. too much work for a cheap made part. if they had just used some sort of solid insulating material first to isolate the etched circuits then used like copper tape for the connections it would have been ok. this problem combined with the rubber membrane style contactors make it just plain junk.

This keypad works fine and has a nice feel. I replaced a cheap membrane keypad and found the pinout to be different on this one. (using the standard keypad library on Arduino)If you have problems, try wiring it as shown in the attached pic.

Works great 👍I used flux on the pads because my eyes bad.

I use this keyboard in many of my projects as the code is easy and makes sense. They can be used in any project that requires simple data entry involving the numbers 0 to 9 along with the letters A to D with pound and star sign ...Thanks for the great manufacturing and service.

After a few weeks of use the keys don't always send data to controller

Once I managed to do a proper soldering job the keypad worked just fine with my ESP2866 Node MCU board.Not much else to say. Feels pretty solid, no complaints. Had to adjust the example code because of the different layout of the ESP2866 board but no big deal.

It would be difficult to make a more promising-looking product that then turns out to be this poor.1. The pads are very difficult to solder -- the trace material (or it's plating) is very reluctant to wet, even with copious amounts of flux. Additionally, this is a single-sided PCB, so if you're intending to solder a 1x10 (or 1x8) row of header pins, it can only protrude from the rear. That fits some scenarios and not others.2. Under normal finger force, and bearing in mind the snap action implies there's contact once snapped, is in the range of 2k to 10k ohms. By applying a lot of force you might get it down to 500ohms. Normally, a product touted as "switches" would have contact resistance in the range of 1 ohm. These switches are likely to either fail to work at all, or work very unreliably, with the built-in pull-up resistors in typical MCUs. This high resistance explains a number of the complaints in other reviews.

I found the resistance of the keypress for the matrix was different for all keys pressed. Sooner or later they will probably cause problems as comments I found about this product being sold on U-buy.com. See attached jpg.