djsundog/circuitpython
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

stmhal: Improve pyb.freq to allow 8 and 16MHz (not usable with USB).

Browse Source 
Also restrict higher frequencies to have a VCO_OUT frequency below
432MHz, as specified in the datasheet.

Docs improved to list allowed frequencies, and explain about USB
stability.
This commit is contained in:
Damien George 2014-11-02 15:10:15 +00:00
parent 039887a0ac
commit 38bd762121
2 changed files with 118 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
docs/library/pyb.rst
View File

@ -103,6 +103,18 @@ Power related functions
supported and the largest supported frequency not greater than
the given sys_freq will be selected.
Supported frequencies are (in MHz): 8, 16, 24, 30, 32, 36, 40, 42, 48,
54, 56, 60, 64, 72, 84, 96, 108, 120, 144, 168.
8MHz uses the HSE (external crystal) directly and 16MHz uses the HSI
(internal oscillator) directly. The higher frequencies use the HSE to
drive the PLL (phase locked loop), and then use the output of the PLL.
Note that if you change the frequency while the USB is enabled then
the USB may become unreliable. It is best to change the frequency
in boot.py, before the USB peripheral is started. Also note that
frequencies below 36MHz do not allow the USB to function correctly.
.. function:: wfi()
Wait for an interrupt.

169
stmhal/modpyb.c
View File

@ -195,80 +195,123 @@ STATIC mp_obj_t pyb_freq(mp_uint_t n_args, const mp_obj_t *args) {
} else {
// set
mp_int_t wanted_sysclk = mp_obj_get_int(args[0]) / 1000000;
// search for a valid PLL configuration that keeps USB at 48MHz
for (; wanted_sysclk > 0; wanted_sysclk--) {
for (mp_uint_t p = 2; p <= 8; p += 2) {
if (wanted_sysclk * p % 48 != 0) {
continue;
}
mp_uint_t q = wanted_sysclk * p / 48;
if (q < 2 || q > 15) {
continue;
}
if (wanted_sysclk * p % (HSE_VALUE / 1000000) != 0) {
continue;
}
mp_uint_t n_by_m = wanted_sysclk * p / (HSE_VALUE / 1000000);
mp_uint_t m = 192 / n_by_m;
while (m < (HSE_VALUE / 2000000) || n_by_m * m < 192) {
m += 1;
}
if (m > (HSE_VALUE / 1000000)) {
continue;
}
mp_uint_t n = n_by_m * m;
if (n < 192 || n > 432) {
continue;
}
// found values!
// default PLL parameters that give 48MHz on PLL48CK
uint32_t m = HSE_VALUE / 1000000, n = 336, p = 2, q = 7;
uint32_t sysclk_source;
// let the USB CDC have a chance to process before we change the clock
HAL_Delay(USBD_CDC_POLLING_INTERVAL + 2);
// the following logic assumes HSE < HSI
if (HSE_VALUE / 1000000 <= wanted_sysclk && wanted_sysclk < HSI_VALUE / 1000000) {
// use HSE as SYSCLK
sysclk_source = RCC_SYSCLKSOURCE_HSE;
} else if (HSI_VALUE / 1000000 <= wanted_sysclk && wanted_sysclk < 24) {
// use HSI as SYSCLK
sysclk_source = RCC_SYSCLKSOURCE_HSI;
} else {
// search for a valid PLL configuration that keeps USB at 48MHz
for (; wanted_sysclk > 0; wanted_sysclk--) {
for (p = 2; p <= 8; p += 2) {
// compute VCO_OUT
mp_uint_t vco_out = wanted_sysclk * p;
// make sure VCO_OUT is between 192MHz and 432MHz
if (vco_out < 192 || vco_out > 432) {
continue;
}
// make sure Q is an integer
if (vco_out % 48 != 0) {
continue;
}
// solve for Q to get PLL48CK at 48MHz
q = vco_out / 48;
// make sure Q is in range
if (q < 2 || q > 15) {
continue;
}
// make sure N/M is an integer
if (vco_out % (HSE_VALUE / 1000000) != 0) {
continue;
}
// solve for N/M
mp_uint_t n_by_m = vco_out / (HSE_VALUE / 1000000);
// solve for M, making sure VCO_IN (=HSE/M) is between 1MHz and 2MHz
m = 192 / n_by_m;
while (m < (HSE_VALUE / 2000000) || n_by_m * m < 192) {
m += 1;
}
if (m > (HSE_VALUE / 1000000)) {
continue;
}
// solve for N
n = n_by_m * m;
// make sure N is in range
if (n < 192 || n > 432) {
continue;
}
// set HSE as system clock source to allow modification of the PLL configuration
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSE;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK) {
goto fail;
// found values!
sysclk_source = RCC_SYSCLKSOURCE_PLLCLK;
goto set_clk;
}
}
nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "can't make valid freq"));
}
// re-configure PLL
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = m;
RCC_OscInitStruct.PLL.PLLN = n;
RCC_OscInitStruct.PLL.PLLP = p;
RCC_OscInitStruct.PLL.PLLQ = q;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
goto fail;
}
set_clk:
//printf("%lu %lu %lu %lu %lu\n", sysclk_source, m, n, p, q);
// set PLL as system clock source
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK) {
goto fail;
}
// let the USB CDC have a chance to process before we change the clock
HAL_Delay(USBD_CDC_POLLING_INTERVAL + 2);
// re-init TIM3 for USB CDC rate
timer_tim3_init();
// desired system clock source is in sysclk_source
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
if (sysclk_source == RCC_SYSCLKSOURCE_PLLCLK) {
// set HSE as system clock source to allow modification of the PLL configuration
// we then change to PLL after re-configuring PLL
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSE;
} else {
// directly set the system clock source as desired
RCC_ClkInitStruct.SYSCLKSource = sysclk_source;
}
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK) {
goto fail;
}
return mp_const_none;
// re-configure PLL
// even if we don't use the PLL for the system clock, we still need it for USB, RNG and SDIO
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = m;
RCC_OscInitStruct.PLL.PLLN = n;
RCC_OscInitStruct.PLL.PLLP = p;
RCC_OscInitStruct.PLL.PLLQ = q;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
goto fail;
}
void __fatal_error(const char *msg);
fail:
__fatal_error("can't change freq");
// set PLL as system clock source if wanted
if (sysclk_source == RCC_SYSCLKSOURCE_PLLCLK) {
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK) {
goto fail;
}
}
nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "can't make valid freq"));
// re-init TIM3 for USB CDC rate
timer_tim3_init();
return mp_const_none;
fail:;
void NORETURN __fatal_error(const char *msg);
__fatal_error("can't change freq");
}
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_freq_obj, 0, 1, pyb_freq);