neazoi
Advanced Member level 6
Hi
I want to investigate the possibility of making a discrete FSK 1200 baud modulator operating from 5v and connected to the TTL UART of an MCU. The circuits have to be made as simple as possible (fewer parts).
Here are two of my rough ideas. I have tested the oscillator parts and they work and they can be varied nicely too.
1200baud is a much higher speed than 300 and I do not know how well these will behave until I test them.
The first circuit uses 2 oscillators and a switch to switch audio outputs.
The second circuit uses a single oscillator and a way to vary it's frequency.
I have thought that at 1200baud, varying the oscillator frequency might cause the oscillator not to be able to switch that fast from one frequency to the other (mark/space), so that is why I have designed the first circuit, which does not mess with the oscillator resonators at all, although I like the simplicity of the second one.
Any comments/suggestions would be valuable so as how to tackle the problem.
I want to investigate the possibility of making a discrete FSK 1200 baud modulator operating from 5v and connected to the TTL UART of an MCU. The circuits have to be made as simple as possible (fewer parts).
Here are two of my rough ideas. I have tested the oscillator parts and they work and they can be varied nicely too.
1200baud is a much higher speed than 300 and I do not know how well these will behave until I test them.
The first circuit uses 2 oscillators and a switch to switch audio outputs.
The second circuit uses a single oscillator and a way to vary it's frequency.
I have thought that at 1200baud, varying the oscillator frequency might cause the oscillator not to be able to switch that fast from one frequency to the other (mark/space), so that is why I have designed the first circuit, which does not mess with the oscillator resonators at all, although I like the simplicity of the second one.
Any comments/suggestions would be valuable so as how to tackle the problem.