Although other venders implement this feature by using RTC, in my H/W(RZ_A1), I cannot use RTC because it does not satisfy the spec of LP Ticker (ms order and low frequency between 8 KHz and 64 KHz).
Therefore I implemented this feature by creating 1024 division by MTU2(Multi function Timer pulse Unit 2) in order to satisfy this spec.
As a result of investigating, the most unaffected channel among MTU2 placed on GR-PEACH and GR-LYCHEE was channel 3, so I use channel 3 for this feature.
- mbed_drv_cfg.h
I added a macro of MTU2 channel to this file for commonalizing code for GR-PEACH and GR-LYCHEE, and referenced it's macro at us_ticker.c.
- targets.json
I added a macro for enabling LP Ticker.
- mtu2.c mtu2.h
I defined fuction of MTU2's clock supply and stop.
Because MTU2 is utilized by pwm driver too, those function were referenced at lp_ticker driver and pwm driver.
- lp_ticker.c lp_ticker_init()
In order to satisfy the LP Ticker spec, I implemented by creating 1024 division by MTU2.
When an interrupt is required, it will be set with ticker_set_interrupt().
- lp_ticker.c lp_ticker_free()
This function stops the counting and powerdown the lp_ticker.
- lp_ticker.c lp_read()
This function returns the timer counter of MTU2.
- lp_ticker.c lp_ticker_set_interrupt()
In order to satisfy specifications, I implemented lp_ticker_set_interrupt() function.
- lp_ticker.c lp_ticker_fire_interrupt()
In order to satisfy spec, I implemented lp_ticker_fire_interrupt() function.
Also I added GIC_EnableIRQ for allowing the interrupt at end of function.
- lp_ticker.c lp_ticker_get_info()
To satisfy the spec, I implemented lp_ticker_get_info() function. The value of freq includes rounding off.
TomoYamanaka