I attempted to read battery voltage manually (by following procedure described in table 14 on user manual, and using the formula with Vmeas at 3.3) but unfortunately values I retrieve results to be quite incoherent (3.29-3.32 range of values i obtain even if battery is low). Therefore I opted for using automatic procedure, that user manual suggests in order to have an estimate of voltage with unloaded battery condition. In order to do this I need a wake-up event, and therefore I attempted to force a sleep with timeout for wake-up, just to read voltage once, but still battery values result to be incoherent. I followed the user manual procedure to force sleep (extracted from low-power listening procedure):
• Set SLEEP_TIM (sleep time period) field in Sub-Register 0x2C:06 – AON_CFG0.
• Set SLEEP_EN (sleep enable) field in Sub-Register 0x2C:06 – AON_CFG0.
• Set WAKE_CNT (wake when sleep counter elapses) field in Sub-Register 0x2C:06 – AON_CFG0.
• Set ONW_RX (on wake turn on the receiver) bit in Sub-Register 0x2C:00 – AON_WCFG.
• Set ONW_LDC (on wake load configurations) bit in Sub-Register 0x2C:00 – AON_WCFG.
Any suggestion to fix this problem?