Merge pull request #15051 from hallard/STM32_LPTIM_Prescaler

Allow to use all STM32 targets prescaler for LPTIM

Author: 0xc0170

targets/TARGET_STM/lp_ticker.c

@@ -242,7 +242,17 @@ void lp_ticker_init(void)
     LptimHandle.State = HAL_LPTIM_STATE_RESET;
     LptimHandle.Init.Clock.Source = LPTIM_CLOCKSOURCE_APBCLOCK_LPOSC;
 #if defined(MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK)
-#if (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 4)
+#if (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 128)
+    LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV128;
+#elif (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 64)
+    LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV64;
+#elif (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 32)
+    LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV32;
+#elif (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 16)
+    LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV16;
+#elif (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 8)
+    LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV8;
+#elif (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 4)
     LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV4;
 #elif (MBED_CONF_TARGET_LPTICKER_LPTIM_CLOCK == 2)
     LptimHandle.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV2;

targets/targets.json

@@ -1256,8 +1256,9 @@
                 "macro_name": "LPTICKER_DELAY_TICKS"
             },
             "lpticker_lptim_clock": {
-                "help": "Default value for LPTIM clock (lpticker_lptim == 1). Value is the dividing factor. Choose 1, 2 or 4",
-                "value": 1
+                "help": "Default value for LPTIM clock (lpticker_lptim == 1). Value is the dividing factor. Choose 1, 2, 4, 8, 16, 32, 64 or 128",
+                "value": 1,
+                "constraint": "Disclaimers : values from 8 to 128 have impacts on mbed-os timer precision and therefore on scheduling. It's not supported by mbed-os. Use it if you know what you're doing such as long low power sleep."
             },
             "gpio_reset_at_init": {
                 "help": "if value set, all GPIO are reset during init",