@KevinWhite has given the correct solution.
Analysis. The underdamped square wave indicates peaks every 2/5 in 1cm at 50ns per cm=division approx. thus 40ns cycle = 25MHz resonance. This is common with long ground lead inductance 0.5~1nH/mm and special coax used in 10:1 probe < 90pF/m. The computed resonance is dependant on the length of the ground lead ...
Your oscilloscope photo indicates that you are able to measure the MCU clock at 16 MHz quite nicely.
You should be using a "10X" probe. It will add some capacitance to the MCU oscillator, which will likely shift its frequency lower. If the MCU oscillator has an input pin and an output pin, probe the output pin.
Your OWON oscilloscope has a time-...
The shape of the waveform won't affect the fundamental frequency of a signal. However an oscilloscope is usually not the correct instrument to accurately measure frequency. It may only have an accuracy of 1% or so.
As @glen_geek points out in his answer some oscilloscopes do have counter/timers built into the instrument that can give high-accuracy (typically ...
You're in worse shape than you think.
It's true, you flip the image axes to take advantage of the higher bandwidth of the scope Y axis. You could then modify your raster scan so that one line goes up, then the next line goes down, then up, etc, in order to avoid the delays caused by the retrace time.
Your problem is the Z-axis modulation frequency, which is ...
Use a unity gain opamp that has the bandwidth
Maybe use an opamp as a buffer, the opamp will need to have more bandwidth than the sensor (and will add in an voltage offset error Vos, so select an opamp with a low voltage offset). The opamp will also need to be able to source more than ~8mA on the output.
Another option would be to use an opamp with gain.
Consider an architecture where you have a memory device acting as a look-up-table: 256 x 8-bits, so you have 8 bits in & 8 bits out. This could hold an arbitrary pattern. This may be one-time programmable, or could be SRAM based and changed under software control.
You could have your existing co-ordinates feeding into this, so you have an output which ...
I've once made a digital second order interpoler with just adders and shifts.
Bezier curves are second order curves. Lines are first order.
To draw lines, you use an integrator :
Pos0 = Initial value
Pos = Pos + Speed * Time
To draw second order curves, you can use two integrators :
Speed0 = Initial value
Pos0 = Initial value
Speed = Speed + Acceleration * ...
The issue was a faulty voltage supply to the scope. It was running off of 5V while it is specified to run off of 9V. I discovered this by checking step 4 of the assembly manual for the scope.
After adjusting my power supply to 9V, the base measurement still was off (but now by around +2V). Using the VPos Adjustment (top right, last page of the manual) fixed ...