I have a robot mower that I'd like to make "smart" by using an Arduino compatible board to mimic key presses via the Blynk app. The control board of the mower is based on a TM1668 chip.
What's the best approach to mimic a key press with my microcontroller? I was thinking of using two BOB-12009 boards (SparkFun Logic Level Converter - Bi-Directional) where the HV is connected to the column and HV1-4 are connected to the buttons. This would allow me to then provide a signal to the LV1-4 pins and that "should" handle the scanning that the TM1668 is doing. I was also thinking another solution would be to use two CD74HC4067 boards to achieve the same goal but that seems a little over kill as 12 of the pins wouldn't be used.
I also don't want to replace the TM1668 with an arduino as I'd like the buttons on the mower to still operate.
I guess I'd try with an opto-coupler across one of the switches to see if that worked. The polarity of the output may be important. You can get packages with 4 opto-couplers. Can multiple buttons be pressed simultaneously ?
I’ll try to draw up a design tomorrow @railgunawesome. @6v6gt no I don’t believe you can press multiple buttons, I’ll look into the optocouplers, what would the difference between those and the converter that I referenced be?
+1 for opto couplers.
Level shifters won't work, because the switches are in a matrix (no ground).
Just wire the opto transistor across the existing switch (polarity matters),
and drive the opto LED via a 1k resistor with an Arduino output pin.
Leo..
An optocoupler is always going to be simpler because you don't have to study the circuit you are connecting to in too much detail. The level shifter and the multiplexer chip switch with respect to a common ground. In the keyboard matrix, from the linked schematic, the rails k1/k2 and the rails seg1/seg2/seg3 must all be kept separate and you cannot arbitrarily select one as ground. (Which is what @Wawa has said as I was composing this)