Initial commit

main.c

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+/* Megumin LED display firmware
+ * Copyright (C) 2018 Sebastian Götte <code@jaseg.net>
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "global.h"
+
+#define RTC_INITIALIZED_REGISTER BKP->DR1
+#define RTC_INITIALIZED_FLAG 1
+
+uint32_t pcg32_random_r() {
+    // *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
+    // Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
+    static uint64_t state = 0xbc422715d3aef60f;
+    static uint64_t inc = 0x6605e3bc6d1a869b; 
+    uint64_t oldstate = state;
+    // Advance internal state
+    state = oldstate * 6364136223846793005ULL + (inc|1);
+    // Calculate output function (XSH RR), uses old state for max ILP
+    uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
+    uint32_t rot = oldstate >> 59u;
+    return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
+}
+
+unsigned char dumb_random() {
+    static unsigned char x=0x66, a=0x05, b=0xe3, c=0xbc;
+    x++; //x is incremented every round and is not affected by any other variable
+    a = (a ^ c ^ x); //note the mix of addition and XOR
+    b = (b + a); //And the use of very few instructions
+    c = (((c + (b >> 1)) ^ a)); // the AES S-Box Operation ensures an even distributon of entropy
+    return (c);
+}
+
+void rtc_write(volatile uint32_t *reg, uint32_t val) {
+    while (!(RTC->CRL & RTC_CRL_RTOFF)) ;
+    RTC->CRL |= RTC_CRL_CNF;
+
+    reg[0] = val>>16;
+    reg[1] = val&0xffff;
+
+    RTC->CRL &= ~RTC_CRL_CNF;
+    while (!(RTC->CRL & RTC_CRL_RTOFF)) ;
+}
+
+void rtc_bus_sync(void) {
+    RTC->CRL &= ~RTC_CRL_RSF;
+    while (!(RTC->CRL & RTC_CRL_RSF)) ;
+}
+
+void rtc_alarm_reset(void) {
+    RTC->CRL &= ~RTC_CRL_ALRF;
+}
+
+void rtc_init(void) {
+    rtc_bus_sync();
+    RTC->CRH = 0;
+    if (!(RTC_INITIALIZED_REGISTER & RTC_INITIALIZED_FLAG)) {
+        rtc_write(&RTC->PRLH, 32768-1);
+        rtc_write(&RTC->CNTH, 0);
+        RTC_INITIALIZED_REGISTER = RTC_INITIALIZED_FLAG;
+    }
+}
+
+void rtc_set_alarm_sec(uint32_t value) {
+    rtc_write(&RTC->ALRH, value);
+}
+
+void rtc_set_alarm_rel_sec(uint32_t value) {
+    uint32_t now = RTC->CNTH<<16 | RTC->CNTL;
+    rtc_set_alarm_sec(now + value);
+}
+
+int main(void){
+    /* We're starting out from HSI@8MHz */
+    SystemCoreClockUpdate();
+    SCB->SCR &= (~SCB_SCR_SLEEPONEXIT_Msk) & SCB_SCR_SLEEPDEEP_Msk; /* Disable for now */
+    for (int i=0; i<1000000; i++) /* about 5s */
+        asm volatile ("nop");
+
+    /* Turn on lots of neat things */
+    RCC->APB2ENR |= RCC_APB2ENR_IOPCEN;
+    RCC->APB1ENR |= RCC_APB1ENR_BKPEN | RCC_APB1ENR_PWREN;
+
+    PWR->CR = PWR_CR_PDDS | PWR_CR_DBP;
+
+    RCC->BDCR = RCC_BDCR_RTCEN | (1<<RCC_BDCR_RTCSEL_Pos) | RCC_BDCR_LSEON;
+    while (!(RCC->BDCR & RCC_BDCR_LSERDY)) ;
+
+    GPIOC->CRH |=
+          (0<<GPIO_CRH_CNF13_Pos) | (2<<GPIO_CRH_MODE13_Pos);  /* PC13 - LED */
+    GPIOC->ODR |= 1<<13;
+
+    rtc_init();
+    rtc_set_alarm_rel_sec(2);
+
+    SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk; /* Use deep sleep mode */
+
+    GPIOC->ODR &= ~(1<<13);
+    for (int i=0; i<100000; i++)
+        asm volatile ("nop");
+    GPIOC->ODR |= 1<<13;
+
+    asm volatile ("wfe");
+    return 42;
+}
+
+void gdb_dump(void) {
+    /* debugger hook */
+}
+
+void NMI_Handler(void) {
+    asm volatile ("bkpt");
+}
+
+void HardFault_Handler(void) __attribute__((naked));
+void HardFault_Handler() {
+    asm volatile ("bkpt");
+}
+
+void SVC_Handler(void) {
+    asm volatile ("bkpt");
+}
+
+
+void PendSV_Handler(void) {
+    asm volatile ("bkpt");
+}
+
+void SysTick_Handler(void) {
+    asm volatile ("bkpt");
+}
+