Sampling rate issue
sp5wwp opened this issue · comments
MCU has to know when to send/read baseband samples from the transceivers. Now, the sample clock is run at the MCU side at 24kHz, and causes occasional sample drops and desynchronization.
Solution (updated Jan 5, 2024):
Connect GPIO2 pin of the transmitting CC1200s to the MCU's EXTI pins, thus letting the TX dictate the baseband transfer speed.
TX GPIO2 (pin 4 of U7) -> MCU PA8 (pin 41 of U14)
New firmware has a #define to handle the bodge wire mod.
The new rpi-interface branch supports the bodge wire mod without the need of having any #defines.
MCU passes baseband samples to the transmitter at the programmed rate (1.5*16=24kHz), trigger signal is provided by the CC1200. The receiver's CLKEN_CFM clock signal is always about 75.7582kHz, regardless of the sample rate setting. Baseband samples from the receiver are therefore read at a rate dictated by TIM7 (24kHz).
TX sample clock fixed in 636a110.