Lostgallifreyan wrote:
Peter Able stuck@home wrote in news:ks2dncC5fJrIAqrJnZ2dnUVZ7s-
:
Fine, but first find a microcontroller with such a fast (minimum 60MHz)
DAC. Even if you do you'll spend many times the cost of a simple
microcontroller plus DDS chip system - and you won't rival the cheaper
system's performance until your DAC can work at several times 60MHz.
Good point. Almost certainly easier to just send step size from CPU to the
accumulator in fast hardware. The step size needs changing far less often
than it needs stepping.
That is what the external DDS chip is doing.
When you require only FM-modulated signals and no sinewave, existing
microcontrollers can do it using their onboard timers and programmable
clock dividers. For example, the Raspberry Pi has been turned into
FM-broadcast and amateur radio shortwave FSK/ASK transmitter, the RF
signal appears (as a square wave) directly on a GPIO pin. Just filter
and amplify, or when you don't ca just connect a random wire as an
antenna to transmit a couple of mW (and harmonics).