diff options
Diffstat (limited to 'software/double_tap_dontboot/double_tap_dontboot.c')
| -rw-r--r-- | software/double_tap_dontboot/double_tap_dontboot.c | 153 |
1 files changed, 0 insertions, 153 deletions
diff --git a/software/double_tap_dontboot/double_tap_dontboot.c b/software/double_tap_dontboot/double_tap_dontboot.c deleted file mode 100644 index 53c2c64..0000000 --- a/software/double_tap_dontboot/double_tap_dontboot.c +++ /dev/null @@ -1,153 +0,0 @@ -// See LICENSE for license details. - -// This is the 'bootloader' which ships on HiFive1 boards, -// at SPI Flash location 0x20000000. -// HiFive1 boards have code burned into their OTP which ends with -// a jump to 0x20000000. The Freedom E SDK and the Arduino IDE -// linker scripts cause user programs to be compiled and -// flashed at 0x20400000. Therefore, this code ultimately jumps -// to 0x20400000, while attempting to leave the machine state as close -// to its reset state as possible. -// -// When compiled in the freedom-e-sdk environment, this code will -// be compiled as a user program at 0x20400000, so will continuously jump to itself. -// It is provided in the freedom-e-sdk mostly for reference purposes, so -// users know what is running on their board. Replacing the bootloader -// at 0x20000000 is not currently supported by the SDK. -// -// These are the instructions for the user of this program, from the -// HiFive1 Getting Started Guide: -// -// This program is designed to allow quick boot, but -// also a "safe" reboot option if a "bad" program -// is flashed into the HiFive1's SPI Flash. A "bad" program -// is one which makes it impossible for the programmer -// to communicate with the HiFive1. For example, a program which -// disables FE310's active clock, or which puts the FE310 to sleep -// with no way of waking it up. Bad programs can always be restarted using -// the RESET button, and using the "safe" bootloader can be halted -// before they perform any unsafe behavior. -// -// To activate "normal" boot mode, press the RESET button on -// the HiFive1. After approximately 1s, the green LED will flash -// for 1/2 second, then the user program will execute. -// -// To activate "safe" boot mode, press the RESET button. When -// the green LED flashes, immediately press the RESET button again. -// After 1 second, the red LED will blink. The user program will not -// execute, and the programmer can connect. To exit "safe" boot mode, -// press the RESET button a final time. - -#include <stdint.h> -#include "platform.h" -#include "encoding.h" - -#ifndef _SIFIVE_HIFIVE1_H -#error "double_tap_dontboot is designed to run on HiFive1 and/or E300 Arty Dev Kit." -#endif - - -#define BACKUP15_MAGIC 0xD027B007 - -#define FINAL_ADDRESS 0x20400000 - -#define RED_LED 22 -#define GREEN_LED 19 - -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). - // By default, this would cause an infinite loop upon exception, which is - // also "safe" behavior and the debugger can connect. - - write_csr(mtvec, 0x0); - - // How did we get here? We only want to execute this code - // on resets (vs waking up from sleep). - 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; - - // 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_CTRL_ADDR + CLINT_MTIME)); - then = now + 32768/500; - while (*((volatile uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIME)) < then) { - asm volatile (""); - } - pwm_val = (pwm_val == 0) ? 255 : (pwm_val -1); - PWM1_REG(PWM_CMP3) = pwm_val << 4; - } - - } // 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); - - // 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_CTRL_ADDR + CLINT_MTIME)); - then = now + 32768/2; - while (*((volatile uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIME)) < then) { - asm volatile (""); - } - - // Re-arm the reset double-tap - AON_REG(AON_BACKUP15) = save; - - } - - // Restore the GPIO Registers to their default - GPIO_REG(GPIO_OUTPUT_VAL) = 0; - GPIO_REG(GPIO_OUTPUT_XOR) = 0; - GPIO_REG(GPIO_OUTPUT_EN) = 0; - - // Jump to "user code" in SPI Flash. - 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); -} |