Dear ST Community,
After reading the SPIRIT1 datasheet and thinking over 2 days on it, I still have a lot of doubts and unclear points. May some help me with the following:
1. XTAL and synthesizer
I have put a 25MHz XTAL on my custom PCB. I saw in the documentation that the SPIRIT-1 also contains an internal oscillator.
1.1. Should I disable the internal one and from which register?
1.2. Which of both feeds the synthesizer eventually?
1.3. What values should I set for RCO_CALIBRATION and VCO_CALIBRATION?
1.4. What is the goal of the calibration from user point of view? What value should I expect
in the register that store the output value after the callibration has finished?
2. 24_26MHz_SELECT bit
When using a 25MHz XTAL and setting the 24_26MHz_SELECT, table 27 states that the low-power RCO with have a value of 33.3kHz.
How will this configuration affect the VCO and any other calculations that I will need to achive RF frequency at 151,4750MHz and channel width of 12.5kHz ?
3. REFDIV and PD_CLKDIV
Shall I disable the REFDIV and PD_CLKDIV dividers for better stability and lower power consumption?
4. WCP [2:0] word
4.1. Do I need the "011" value for 151,4750MHz freq? And what's the meaning of it?
4.2. How does the pump current relate to the target RF frequency?
5. Channel width
5.1. Is the CHSPACE actually equal to the channel width?
In my case, as mentioned above, I need center frequency of 151,4750MHz, lower 151,46875MHz and upper 151,48125MHz (=12.5kHz channel widht)?
6. TX
Can I transmit a single byte, without the need to fill the whole queue in?
7. RX
7.1. Related to point 6, can I receive a singe byte and get a an interrupt saying "A new byte arrived in the RX FIFO"
7.2. If so, can I expose the interrupt to a pin that will get toggled accordingly?
8. Framing modes and FIFOs
Do only the payload bytes get in the queue? Or some header bytes may be included as well in some modes?
9. Testing
Initially, I want to connect the RF output to a spectrum analyzer and test CW in "PN9" mode. Do I need to use the "Start to transmit" (from "Table 21. Commands list") command to launch the transmission in CW mode?
And finally, I will be really grateful if someone can provide a summarized register configuration with the most necessary settings to get started!
Thank you in advance!
