diff options
| -rw-r--r-- | software/double_tap_dontboot/double_tap_dontboot.c | 116 |
1 files changed, 59 insertions, 57 deletions
diff --git a/software/double_tap_dontboot/double_tap_dontboot.c b/software/double_tap_dontboot/double_tap_dontboot.c index 575e748..0cae5b5 100644 --- a/software/double_tap_dontboot/double_tap_dontboot.c +++ b/software/double_tap_dontboot/double_tap_dontboot.c @@ -53,7 +53,6 @@ int main(void) { uint64_t now; uint64_t then; - // Restore the default mtvec (which may have been set by initialization // code, depending on the environment in which this C code is compiled). @@ -67,71 +66,71 @@ int main(void) if ((AON_REG(AON_PMUCAUSE) & AON_PMUCAUSE_WAKEUPCAUSE) == AON_WAKEUPCAUSE_RESET) { - if (AON_REG(AON_BACKUP15) == BACKUP15_MAGIC) { - // Reset was "double-tapped". - - // Re-arm the reset double-tap - AON_REG(AON_BACKUP15) = 0; - - // PWM Red LED - - GPIO_REG(GPIO_IOF_EN) |= (1 << RED_LED); - GPIO_REG(GPIO_OUTPUT_XOR) &= ~(1 << RED_LED); - GPIO_REG(GPIO_IOF_SEL) |= (1 << RED_LED); - - GPIO_REG(GPIO_OUTPUT_VAL) &= ~(1 << GREEN_LED); - GPIO_REG(GPIO_OUTPUT_XOR) &= ~(1 << GREEN_LED); - GPIO_REG(GPIO_OUTPUT_EN) &= ~(1 << GREEN_LED); - - PWM1_REG(PWM_CFG) = 0; - PWM1_REG(PWM_COUNT) = 0; - PWM1_REG(PWM_CMP0) = 0xFF; - PWM1_REG(PWM_CMP3) = 0xFF; - PWM1_REG(PWM_CFG) = PWM_CFG_ENALWAYS; - - int pwm_val = 255; + if (AON_REG(AON_BACKUP15) == BACKUP15_MAGIC) { + // Reset was "double-tapped". + + // Re-arm the reset double-tap + AON_REG(AON_BACKUP15) = 0; + + // PWM Red LED + + GPIO_REG(GPIO_IOF_EN) |= (1 << RED_LED); + GPIO_REG(GPIO_OUTPUT_XOR) &= ~(1 << RED_LED); + GPIO_REG(GPIO_IOF_SEL) |= (1 << RED_LED); + + GPIO_REG(GPIO_OUTPUT_VAL) &= ~(1 << GREEN_LED); + GPIO_REG(GPIO_OUTPUT_XOR) &= ~(1 << GREEN_LED); + GPIO_REG(GPIO_OUTPUT_EN) &= ~(1 << GREEN_LED); + + PWM1_REG(PWM_CFG) = 0; + PWM1_REG(PWM_COUNT) = 0; + PWM1_REG(PWM_CMP0) = 0xFF; + PWM1_REG(PWM_CMP3) = 0xFF; + PWM1_REG(PWM_CFG) = PWM_CFG_ENALWAYS; + + int pwm_val = 255; - // Wait for debugger or another RESET press. - while(1){ - - // Make the PWM a fade. This is preferable to just a PWM blink - // because it makes it clear that the processor is actually - // running this code, not just the PWM hardware. - - now = *((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)); - then = now + 32768/500; - while (*((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)) < then) { - asm volatile (""); - } - pwm_val = (pwm_val == 0) ? 255 : (pwm_val -1); - PWM1_REG(PWM_CMP3) = pwm_val << 4; - } + // Wait for debugger or another RESET press. + while(1){ + + // Make the PWM a fade. This is preferable to just a PWM blink + // because it makes it clear that the processor is actually + // running this code, not just the PWM hardware. + + now = *((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)); + then = now + 32768/500; + while (*((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)) < then) { + asm volatile (""); + } + pwm_val = (pwm_val == 0) ? 255 : (pwm_val -1); + PWM1_REG(PWM_CMP3) = pwm_val << 4; + } - } // If Magic + } // If Magic // Turn on Green LED to indicate time-to-double-tap // LEDs are Active-Low - GPIO_REG(GPIO_OUTPUT_VAL) |= (1 << GREEN_LED); - GPIO_REG(GPIO_OUTPUT_XOR) |= (1 << GREEN_LED); - GPIO_REG(GPIO_OUTPUT_EN) |= (1 << GREEN_LED); + GPIO_REG(GPIO_OUTPUT_VAL) |= (1 << GREEN_LED); + GPIO_REG(GPIO_OUTPUT_XOR) |= (1 << GREEN_LED); + GPIO_REG(GPIO_OUTPUT_EN) |= (1 << GREEN_LED); - // Re-arm the reset double-tap - uint32_t save = AON_REG(AON_BACKUP15); + // Re-arm the reset double-tap + uint32_t save = AON_REG(AON_BACKUP15); - AON_REG(AON_BACKUP15) = BACKUP15_MAGIC; - - // Wait 500 ms. If reset is tapped at this point, - // we will execute the "magic" loop above. - now = *((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)); - then = now + 32768/2; - while (*((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)) < then) { - asm volatile (""); - } + AON_REG(AON_BACKUP15) = BACKUP15_MAGIC; + + // Wait 500 ms. If reset is tapped at this point, + // we will execute the "magic" loop above. + now = *((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)); + then = now + 32768/2; + while (*((volatile uint64_t*) (CLINT_BASE_ADDR + CLINT_MTIME)) < then) { + asm volatile (""); + } - // Re-arm the reset double-tap - AON_REG(AON_BACKUP15) = save; + // Re-arm the reset double-tap + AON_REG(AON_BACKUP15) = save; - } + } // Restore the GPIO Registers to their default GPIO_REG(GPIO_OUTPUT_VAL) = 0; @@ -142,5 +141,8 @@ int main(void) void (*pgm_start)(void) = (void*) FINAL_ADDRESS; pgm_start(); + // This value is meaningless, but + // since this code should never be reached, + // make it non-zero. return (1234567); } |