Primitive function generator for Arduino with LCD keypad shield =============================================================== LCD Keypad shield version. Supports "DF Robot" v1.0 boards. These shields are available for around $10 shipped on eBay and other places. The newer versions use different resistance values for the keys, check their sample code. I will try to add a #define for the new boards so you dont' have to edit the values. I don't have a newer board for testing yet. The select button will start / stop the generator at any time. Use the up/down buttons to move between function/rate/start. Use the left/right buttons to change the values. On the start menu press the right button to start. Depending on the function you select, the valid rates will change. The square wave uses Arduino clock (divided in half) directly so it supports up to 8MHz on a 16MHz Arduino. The patterns are done via an ISR and max out at 100KHz. The bit rate is 100KHz and it sends 8 bits so the cycle rate between two bits toggling is only 50KHz. I might update the rates later to be more accurate, but for now this is how it is setup. The square wave is quite precise as it is just hardware driven directly off your clock. If you have an accurate crystal, you have accurate output. The pattern generation is accurate down to 500Hz. Below 500Hz the clock division error skews it slightly. You can see it using a logic analyzer. Square wave -- pin is toggled on/off the same amount of time. Narrow pulse -- pin is on 1 bit, off 7. Wide pulse -- pin is on 7 bits, off 1. Directional -- Not sure what to call this, but basically it is a pattern that will tell you if your scope or logic analyzer is presenting the data backwards or something. Mostly useful for my logic_analyzer development.