This is a demo of the simple FM transmitter using PSoC5 (KIT-059). The project is very simple and uses no software code. AC input from the audio source is amplified (0-4V) and applied to the varactor diode, which controls frequency of the ceramic resonator (4.19 MHz). PSoC5 PLL is set to operate at 75.4MHz, which is 18x harmonic of the XTAL. It appears that PSoC5 internal PLL lock time is quite short (<250us), so that PLL can track the audio frequency (up to ~5kHz), though it less efficient at high range. Antenna is made from a 2" piece of wire, which is connected directly to the BUS_CLOCK output. There is no tank circuit, so transmitter emits on many harmonics of the main (1x, 3x, 5x...). Fortunately, 75MHz and 226MHz regions are empty, and emitted power is rather low (<100nW) so there is no issues with FCC.
Any other ceramic resonator will work, the 4.19MHz is what i had at hands. PLL will lock to any XTAL with frequency >=4MHz. The varactor is also not specific, look for any which adjusts in 10-100pf in 0-4V range (hyperabrupt type). Since PLL feedback decreases with modulation frequency, adding simple CR high-pass filter at audio input with Fcutoff~1-4kHz improves FM output.
RTL-SDR receiver dongle was used to receive the signal, and SDR# for visualization. See official website for details:
The errors appear on the project annotation page, which is optional, and does not affect performance. The annotation page KIT-059 can be simply disabled or deleted.
The errors arise due to Creator unable to find custom components from the old Annotation library v0.0, which is obsolete. If necessary, you can download and install it from the link above. New version of the PSoC Annotation Library v1.0 can be downloaded here
The output produces multiple harmonics of the base frequency (in the above demo it is 75.4MHz), and I saw some signals in ~400MHz range also using RTLSDR dongle. You have to adjust PSoC bus_clk to match 433MHz.
The resonator used above is ceramic type, 4.19MHz center frequency. It has wider bandwidth than quartz, and allows for about 1% tuning using varactor diode. Notet that PSoC can lock to resonator in the range between 4MHz to ~28MHz. I am not sure where the 433MHz SAW filter can be placed.