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SAM54 Xplained Pro: reduce board setup code for maintenance

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The board now runs off the internal oscillator at 48 MHz.
This is sufficient to run the TinyUSB examples.

A better performing clock setup is keep in the file as init_clock_xtal()
as an example.
This commit is contained in:
Jean Gressmann 2021-03-21 09:43:29 +01:00
parent a2006ce214
commit 1a5a113655
2 changed files with 19 additions and 5 deletions
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2
hw/bsp/same54xplainedpro/board.mk
View File

@ -1,6 +1,6 @@
DEPS_SUBMODULES = hw/mcu/microchip
CONF_CPU_FREQUENCY ?= 120000000
CONF_CPU_FREQUENCY ?= 48000000
CFLAGS += \
-mthumb \

22
hw/bsp/same54xplainedpro/same54xplainedpro.c
View File

@ -59,7 +59,19 @@ void USB_3_Handler(void)
#define BUTTON_PIN PIN_PB31
#define BOARD_SERCOM SERCOM2
static inline void init_clock(void)
/** Initializes the clocks from the external 12 MHz crystal
*
* The goal of this setup is to preserve the second PLL
* for the application code while still having a reasonable
* 48 MHz clock for USB / UART.
*
* GCLK0: CONF_CPU_FREQUENCY (default 120 MHz) from PLL0
* GCLK1: unused
* GCLK2: 12 MHz from XOSC1
* DFLL48M: closed loop from GLCK2
* GCLK3: 48 MHz
*/
static inline void init_clock_xtal(void)
{
/* configure for a 12MHz crystal connected to XIN1/XOUT1 */
OSCCTRL->XOSCCTRL[1].reg =
@ -118,13 +130,14 @@ static inline void init_clock(void)
while(1 == GCLK->SYNCBUSY.bit.GENCTRL3);
}
/* Initialize SERCOM2 for 115200 bps 8N1 using a 48 MHz clock */
static inline void uart_init(void)
{
gpio_set_pin_function(PIN_PB24, PINMUX_PB24D_SERCOM2_PAD1);
gpio_set_pin_function(PIN_PB25, PINMUX_PB25D_SERCOM2_PAD0);
MCLK->APBBMASK.bit.SERCOM2_ = 1;
GCLK->PCHCTRL[SERCOM2_GCLK_ID_CORE].reg = GCLK_PCHCTRL_GEN_GCLK3 | GCLK_PCHCTRL_CHEN;
GCLK->PCHCTRL[SERCOM2_GCLK_ID_CORE].reg = GCLK_PCHCTRL_GEN_GCLK0 | GCLK_PCHCTRL_CHEN;
BOARD_SERCOM->USART.CTRLA.bit.SWRST = 1; /* reset and disable SERCOM -> enable configuration */
while (BOARD_SERCOM->USART.SYNCBUSY.bit.SWRST);
@ -167,7 +180,8 @@ static inline void uart_send_str(const char* text)
void board_init(void)
{
init_clock();
// Uncomment this line to run off the XTAL
// init_clock_xtal();
SystemCoreClock = CONF_CPU_FREQUENCY;
@ -218,7 +232,7 @@ void board_init(void)
* The USB module requires a GCLK_USB of 48 MHz ~ 0.25% clock
* for low speed and full speed operation.
*/
hri_gclk_write_PCHCTRL_reg(GCLK, USB_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK3_Val | GCLK_PCHCTRL_CHEN);
hri_gclk_write_PCHCTRL_reg(GCLK, USB_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK0_Val | GCLK_PCHCTRL_CHEN);
hri_mclk_set_AHBMASK_USB_bit(MCLK);
hri_mclk_set_APBBMASK_USB_bit(MCLK);