1 /* Teensyduino Core Library
2 * http://www.pjrc.com/teensy/
3 * Copyright (c) 2013 PJRC.COM, LLC.
5 * Permission is hereby granted, free of charge, to any person obtaining
6 * a copy of this software and associated documentation files (the
7 * "Software"), to deal in the Software without restriction, including
8 * without limitation the rights to use, copy, modify, merge, publish,
9 * distribute, sublicense, and/or sell copies of the Software, and to
10 * permit persons to whom the Software is furnished to do so, subject to
11 * the following conditions:
13 * 1. The above copyright notice and this permission notice shall be
14 * included in all copies or substantial portions of the Software.
16 * 2. If the Software is incorporated into a build system that allows
17 * selection among a list of target devices, then similar target
18 * devices manufactured by PJRC.COM must be included in the list of
19 * target devices and selectable in the same manner.
21 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
22 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
24 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
25 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
26 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
27 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
34 extern unsigned long _stext;
35 extern unsigned long _etext;
36 extern unsigned long _sdata;
37 extern unsigned long _edata;
38 extern unsigned long _sbss;
39 extern unsigned long _ebss;
40 extern unsigned long _estack;
41 //extern void __init_array_start(void);
42 //extern void __init_array_end(void);
43 extern int main (void);
44 void ResetHandler(void);
45 void _init_Teensyduino_internal_(void);
46 void __libc_init_array(void);
52 // keep polling some communication while in fault
53 // mode, so we don't completely die.
54 if (SIM_SCGC4 & SIM_SCGC4_USBOTG) usb_isr();
55 if (SIM_SCGC4 & SIM_SCGC4_UART0) uart0_status_isr();
56 if (SIM_SCGC4 & SIM_SCGC4_UART1) uart1_status_isr();
57 if (SIM_SCGC4 & SIM_SCGC4_UART2) uart2_status_isr();
66 extern volatile uint32_t systick_millis_count;
67 void systick_default_isr(void)
69 systick_millis_count++;
72 void nmi_isr(void) __attribute__ ((weak, alias("unused_isr")));
73 void hard_fault_isr(void) __attribute__ ((weak, alias("unused_isr")));
74 void memmanage_fault_isr(void) __attribute__ ((weak, alias("unused_isr")));
75 void bus_fault_isr(void) __attribute__ ((weak, alias("unused_isr")));
76 void usage_fault_isr(void) __attribute__ ((weak, alias("unused_isr")));
77 void svcall_isr(void) __attribute__ ((weak, alias("unused_isr")));
78 void debugmonitor_isr(void) __attribute__ ((weak, alias("unused_isr")));
79 void pendablesrvreq_isr(void) __attribute__ ((weak, alias("unused_isr")));
80 void systick_isr(void) __attribute__ ((weak, alias("systick_default_isr")));
82 void dma_ch0_isr(void) __attribute__ ((weak, alias("unused_isr")));
83 void dma_ch1_isr(void) __attribute__ ((weak, alias("unused_isr")));
84 void dma_ch2_isr(void) __attribute__ ((weak, alias("unused_isr")));
85 void dma_ch3_isr(void) __attribute__ ((weak, alias("unused_isr")));
86 void dma_ch4_isr(void) __attribute__ ((weak, alias("unused_isr")));
87 void dma_ch5_isr(void) __attribute__ ((weak, alias("unused_isr")));
88 void dma_ch6_isr(void) __attribute__ ((weak, alias("unused_isr")));
89 void dma_ch7_isr(void) __attribute__ ((weak, alias("unused_isr")));
90 void dma_ch8_isr(void) __attribute__ ((weak, alias("unused_isr")));
91 void dma_ch9_isr(void) __attribute__ ((weak, alias("unused_isr")));
92 void dma_ch10_isr(void) __attribute__ ((weak, alias("unused_isr")));
93 void dma_ch11_isr(void) __attribute__ ((weak, alias("unused_isr")));
94 void dma_ch12_isr(void) __attribute__ ((weak, alias("unused_isr")));
95 void dma_ch13_isr(void) __attribute__ ((weak, alias("unused_isr")));
96 void dma_ch14_isr(void) __attribute__ ((weak, alias("unused_isr")));
97 void dma_ch15_isr(void) __attribute__ ((weak, alias("unused_isr")));
98 void dma_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
99 void mcm_isr(void) __attribute__ ((weak, alias("unused_isr")));
100 void flash_cmd_isr(void) __attribute__ ((weak, alias("unused_isr")));
101 void flash_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
102 void low_voltage_isr(void) __attribute__ ((weak, alias("unused_isr")));
103 void wakeup_isr(void) __attribute__ ((weak, alias("unused_isr")));
104 void watchdog_isr(void) __attribute__ ((weak, alias("unused_isr")));
105 void i2c0_isr(void) __attribute__ ((weak, alias("unused_isr")));
106 void i2c1_isr(void) __attribute__ ((weak, alias("unused_isr")));
107 void i2c2_isr(void) __attribute__ ((weak, alias("unused_isr")));
108 void spi0_isr(void) __attribute__ ((weak, alias("unused_isr")));
109 void spi1_isr(void) __attribute__ ((weak, alias("unused_isr")));
110 void spi2_isr(void) __attribute__ ((weak, alias("unused_isr")));
111 void sdhc_isr(void) __attribute__ ((weak, alias("unused_isr")));
112 void can0_message_isr(void) __attribute__ ((weak, alias("unused_isr")));
113 void can0_bus_off_isr(void) __attribute__ ((weak, alias("unused_isr")));
114 void can0_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
115 void can0_tx_warn_isr(void) __attribute__ ((weak, alias("unused_isr")));
116 void can0_rx_warn_isr(void) __attribute__ ((weak, alias("unused_isr")));
117 void can0_wakeup_isr(void) __attribute__ ((weak, alias("unused_isr")));
118 void i2s0_tx_isr(void) __attribute__ ((weak, alias("unused_isr")));
119 void i2s0_rx_isr(void) __attribute__ ((weak, alias("unused_isr")));
120 void uart0_lon_isr(void) __attribute__ ((weak, alias("unused_isr")));
121 void uart0_status_isr(void) __attribute__ ((weak, alias("unused_isr")));
122 void uart0_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
123 void uart1_status_isr(void) __attribute__ ((weak, alias("unused_isr")));
124 void uart1_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
125 void uart2_status_isr(void) __attribute__ ((weak, alias("unused_isr")));
126 void uart2_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
127 void uart3_status_isr(void) __attribute__ ((weak, alias("unused_isr")));
128 void uart3_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
129 void uart4_status_isr(void) __attribute__ ((weak, alias("unused_isr")));
130 void uart4_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
131 void uart5_status_isr(void) __attribute__ ((weak, alias("unused_isr")));
132 void uart5_error_isr(void) __attribute__ ((weak, alias("unused_isr")));
133 void adc0_isr(void) __attribute__ ((weak, alias("unused_isr")));
134 void adc1_isr(void) __attribute__ ((weak, alias("unused_isr")));
135 void cmp0_isr(void) __attribute__ ((weak, alias("unused_isr")));
136 void cmp1_isr(void) __attribute__ ((weak, alias("unused_isr")));
137 void cmp2_isr(void) __attribute__ ((weak, alias("unused_isr")));
138 void ftm0_isr(void) __attribute__ ((weak, alias("unused_isr")));
139 void ftm1_isr(void) __attribute__ ((weak, alias("unused_isr")));
140 void ftm2_isr(void) __attribute__ ((weak, alias("unused_isr")));
141 void ftm3_isr(void) __attribute__ ((weak, alias("unused_isr")));
142 void cmt_isr(void) __attribute__ ((weak, alias("unused_isr")));
143 void rtc_alarm_isr(void) __attribute__ ((weak, alias("unused_isr")));
144 void rtc_seconds_isr(void) __attribute__ ((weak, alias("unused_isr")));
145 void pit0_isr(void) __attribute__ ((weak, alias("unused_isr")));
146 void pit1_isr(void) __attribute__ ((weak, alias("unused_isr")));
147 void pit2_isr(void) __attribute__ ((weak, alias("unused_isr")));
148 void pit3_isr(void) __attribute__ ((weak, alias("unused_isr")));
149 void pdb_isr(void) __attribute__ ((weak, alias("unused_isr")));
150 void usb_isr(void) __attribute__ ((weak, alias("unused_isr")));
151 void usb_charge_isr(void) __attribute__ ((weak, alias("unused_isr")));
152 void dac0_isr(void) __attribute__ ((weak, alias("unused_isr")));
153 void dac1_isr(void) __attribute__ ((weak, alias("unused_isr")));
154 void tsi0_isr(void) __attribute__ ((weak, alias("unused_isr")));
155 void mcg_isr(void) __attribute__ ((weak, alias("unused_isr")));
156 void lptmr_isr(void) __attribute__ ((weak, alias("unused_isr")));
157 void porta_isr(void) __attribute__ ((weak, alias("unused_isr")));
158 void portb_isr(void) __attribute__ ((weak, alias("unused_isr")));
159 void portc_isr(void) __attribute__ ((weak, alias("unused_isr")));
160 void portd_isr(void) __attribute__ ((weak, alias("unused_isr")));
161 void porte_isr(void) __attribute__ ((weak, alias("unused_isr")));
162 void software_isr(void) __attribute__ ((weak, alias("unused_isr")));
165 // TODO: create AVR-stype ISR() macro, with default linkage to undefined handler
167 __attribute__ ((section(".vectors"), used))
168 void (* const gVectors[])(void) =
170 (void (*)(void))((unsigned long)&_estack), // 0 ARM: Initial Stack Pointer
171 ResetHandler, // 1 ARM: Initial Program Counter
172 nmi_isr, // 2 ARM: Non-maskable Interrupt (NMI)
173 hard_fault_isr, // 3 ARM: Hard Fault
174 memmanage_fault_isr, // 4 ARM: MemManage Fault
175 bus_fault_isr, // 5 ARM: Bus Fault
176 usage_fault_isr, // 6 ARM: Usage Fault
181 svcall_isr, // 11 ARM: Supervisor call (SVCall)
182 debugmonitor_isr, // 12 ARM: Debug Monitor
184 pendablesrvreq_isr, // 14 ARM: Pendable req serv(PendableSrvReq)
185 systick_isr, // 15 ARM: System tick timer (SysTick)
186 #if defined(_mk20dx128_)
187 dma_ch0_isr, // 16 DMA channel 0 transfer complete
188 dma_ch1_isr, // 17 DMA channel 1 transfer complete
189 dma_ch2_isr, // 18 DMA channel 2 transfer complete
190 dma_ch3_isr, // 19 DMA channel 3 transfer complete
191 dma_error_isr, // 20 DMA error interrupt channel
192 unused_isr, // 21 DMA --
193 flash_cmd_isr, // 22 Flash Memory Command complete
194 flash_error_isr, // 23 Flash Read collision
195 low_voltage_isr, // 24 Low-voltage detect/warning
196 wakeup_isr, // 25 Low Leakage Wakeup
197 watchdog_isr, // 26 Both EWM and WDOG interrupt
200 i2s0_tx_isr, // 29 I2S0 Transmit
201 i2s0_rx_isr, // 30 I2S0 Receive
202 uart0_lon_isr, // 31 UART0 CEA709.1-B (LON) status
203 uart0_status_isr, // 32 UART0 status
204 uart0_error_isr, // 33 UART0 error
205 uart1_status_isr, // 34 UART1 status
206 uart1_error_isr, // 35 UART1 error
207 uart2_status_isr, // 36 UART2 status
208 uart2_error_isr, // 37 UART2 error
215 rtc_alarm_isr, // 44 RTC Alarm interrupt
216 rtc_seconds_isr, // 45 RTC Seconds interrupt
217 pit0_isr, // 46 PIT Channel 0
218 pit1_isr, // 47 PIT Channel 1
219 pit2_isr, // 48 PIT Channel 2
220 pit3_isr, // 49 PIT Channel 3
221 pdb_isr, // 50 PDB Programmable Delay Block
222 usb_isr, // 51 USB OTG
223 usb_charge_isr, // 52 USB Charger Detect
226 lptmr_isr, // 55 Low Power Timer
227 porta_isr, // 56 Pin detect (Port A)
228 portb_isr, // 57 Pin detect (Port B)
229 portc_isr, // 58 Pin detect (Port C)
230 portd_isr, // 59 Pin detect (Port D)
231 porte_isr, // 60 Pin detect (Port E)
232 software_isr, // 61 Software interrupt
233 #elif defined(_mk20dx256_)
234 dma_ch0_isr, // 16 DMA channel 0 transfer complete
235 dma_ch1_isr, // 17 DMA channel 1 transfer complete
236 dma_ch2_isr, // 18 DMA channel 2 transfer complete
237 dma_ch3_isr, // 19 DMA channel 3 transfer complete
238 dma_ch4_isr, // 20 DMA channel 4 transfer complete
239 dma_ch5_isr, // 21 DMA channel 5 transfer complete
240 dma_ch6_isr, // 22 DMA channel 6 transfer complete
241 dma_ch7_isr, // 23 DMA channel 7 transfer complete
242 dma_ch8_isr, // 24 DMA channel 8 transfer complete
243 dma_ch9_isr, // 25 DMA channel 9 transfer complete
244 dma_ch10_isr, // 26 DMA channel 10 transfer complete
245 dma_ch11_isr, // 27 DMA channel 10 transfer complete
246 dma_ch12_isr, // 28 DMA channel 10 transfer complete
247 dma_ch13_isr, // 29 DMA channel 10 transfer complete
248 dma_ch14_isr, // 30 DMA channel 10 transfer complete
249 dma_ch15_isr, // 31 DMA channel 10 transfer complete
250 dma_error_isr, // 32 DMA error interrupt channel
252 flash_cmd_isr, // 34 Flash Memory Command complete
253 flash_error_isr, // 35 Flash Read collision
254 low_voltage_isr, // 36 Low-voltage detect/warning
255 wakeup_isr, // 37 Low Leakage Wakeup
256 watchdog_isr, // 38 Both EWM and WDOG interrupt
263 can0_message_isr, // 45 CAN OR'ed Message buffer (0-15)
264 can0_bus_off_isr, // 46 CAN Bus Off
265 can0_error_isr, // 47 CAN Error
266 can0_tx_warn_isr, // 48 CAN Transmit Warning
267 can0_rx_warn_isr, // 49 CAN Receive Warning
268 can0_wakeup_isr, // 50 CAN Wake Up
269 i2s0_tx_isr, // 51 I2S0 Transmit
270 i2s0_rx_isr, // 52 I2S0 Receive
278 uart0_lon_isr, // 60 UART0 CEA709.1-B (LON) status
279 uart0_status_isr, // 61 UART0 status
280 uart0_error_isr, // 62 UART0 error
281 uart1_status_isr, // 63 UART1 status
282 uart1_error_isr, // 64 UART1 error
283 uart2_status_isr, // 65 UART2 status
284 uart2_error_isr, // 66 UART2 error
300 rtc_alarm_isr, // 82 RTC Alarm interrupt
301 rtc_seconds_isr, // 83 RTC Seconds interrupt
302 pit0_isr, // 84 PIT Channel 0
303 pit1_isr, // 85 PIT Channel 1
304 pit2_isr, // 86 PIT Channel 2
305 pit3_isr, // 87 PIT Channel 3
306 pdb_isr, // 88 PDB Programmable Delay Block
307 usb_isr, // 89 USB OTG
308 usb_charge_isr, // 90 USB Charger Detect
319 lptmr_isr, // 101 Low Power Timer
320 unused_isr, // 102 --
321 porta_isr, // 103 Pin detect (Port A)
322 portb_isr, // 104 Pin detect (Port B)
323 portc_isr, // 105 Pin detect (Port C)
324 portd_isr, // 106 Pin detect (Port D)
325 porte_isr, // 107 Pin detect (Port E)
326 unused_isr, // 108 --
327 unused_isr, // 109 --
328 software_isr, // 110 Software interrupt
336 __attribute__ ((section(".flashconfig"), used))
337 const uint8_t flashconfigbytes[16] = {
338 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
339 0xFF, 0xFF, 0xFF, 0xFF, 0xFE, 0xFF, 0xFF, 0xFF
343 // Automatically initialize the RTC. When the build defines the compile
344 // time, and the user has added a crystal, the RTC will automatically
345 // begin at the time of the first upload.
347 #define TIME_T 1349049600 // default 1 Oct 2012 (never used, Arduino sets this)
349 extern void rtc_set(unsigned long t);
353 static void startup_unused_hook(void) {}
354 void startup_early_hook(void) __attribute__ ((weak, alias("startup_unused_hook")));
355 void startup_late_hook(void) __attribute__ ((weak, alias("startup_unused_hook")));
358 __attribute__ ((section(".startup")))
359 void ResetHandler(void)
361 uint32_t *src = &_etext;
362 uint32_t *dest = &_sdata;
365 WDOG_UNLOCK = WDOG_UNLOCK_SEQ1;
366 WDOG_UNLOCK = WDOG_UNLOCK_SEQ2;
367 WDOG_STCTRLH = WDOG_STCTRLH_ALLOWUPDATE;
368 startup_early_hook();
370 // enable clocks to always-used peripherals
371 #if defined(_mk20dx128_)
372 SIM_SCGC5 = 0x00043F82; // clocks active to all GPIO
373 SIM_SCGC6 = SIM_SCGC6_RTC | SIM_SCGC6_FTM0 | SIM_SCGC6_FTM1 | SIM_SCGC6_ADC0 | SIM_SCGC6_FTFL;
374 #elif defined(_mk20dx256_)
375 SIM_SCGC3 = SIM_SCGC3_ADC1 | SIM_SCGC3_FTM2;
376 SIM_SCGC5 = 0x00043F82; // clocks active to all GPIO
377 SIM_SCGC6 = SIM_SCGC6_RTC | SIM_SCGC6_FTM0 | SIM_SCGC6_FTM1 | SIM_SCGC6_ADC0 | SIM_SCGC6_FTFL;
380 // if the RTC oscillator isn't enabled, get it started early
381 if (!(RTC_CR & RTC_CR_OSCE)) {
383 RTC_CR = RTC_CR_SC16P | RTC_CR_SC4P | RTC_CR_OSCE;
386 // release I/O pins hold, if we woke up from VLLS mode
387 if (PMC_REGSC & PMC_REGSC_ACKISO) PMC_REGSC |= PMC_REGSC_ACKISO;
389 // TODO: do this while the PLL is waiting to lock....
390 while (dest < &_edata) *dest++ = *src++;
392 while (dest < &_ebss) *dest++ = 0;
393 SCB_VTOR = 0; // use vector table in flash
395 // default all interrupts to medium priority level
396 for (i=0; i < NVIC_NUM_INTERRUPTS; i++) NVIC_SET_PRIORITY(i, 128);
399 // enable capacitors for crystal
400 OSC0_CR = OSC_SC8P | OSC_SC2P;
401 // enable osc, 8-32 MHz range, low power mode
402 MCG_C2 = MCG_C2_RANGE0(2) | MCG_C2_EREFS;
403 // switch to crystal as clock source, FLL input = 16 MHz / 512
404 MCG_C1 = MCG_C1_CLKS(2) | MCG_C1_FRDIV(4);
405 // wait for crystal oscillator to begin
406 while ((MCG_S & MCG_S_OSCINIT0) == 0) ;
407 // wait for FLL to use oscillator
408 while ((MCG_S & MCG_S_IREFST) != 0) ;
409 // wait for MCGOUT to use oscillator
410 while ((MCG_S & MCG_S_CLKST_MASK) != MCG_S_CLKST(2)) ;
411 // now we're in FBE mode
412 // config PLL input for 16 MHz Crystal / 4 = 4 MHz
413 MCG_C5 = MCG_C5_PRDIV0(3);
414 // config PLL for 96 MHz output
415 MCG_C6 = MCG_C6_PLLS | MCG_C6_VDIV0(0);
416 // wait for PLL to start using xtal as its input
417 while (!(MCG_S & MCG_S_PLLST)) ;
418 // wait for PLL to lock
419 while (!(MCG_S & MCG_S_LOCK0)) ;
420 // now we're in PBE mode
421 #if F_CPU == 96000000
422 // config divisors: 96 MHz core, 48 MHz bus, 24 MHz flash
423 SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(0) | SIM_CLKDIV1_OUTDIV2(1) | SIM_CLKDIV1_OUTDIV4(3);
424 #elif F_CPU == 48000000
425 // config divisors: 48 MHz core, 48 MHz bus, 24 MHz flash
426 SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(1) | SIM_CLKDIV1_OUTDIV2(1) | SIM_CLKDIV1_OUTDIV4(3);
427 #elif F_CPU == 24000000
428 // config divisors: 24 MHz core, 24 MHz bus, 24 MHz flash
429 SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(3) | SIM_CLKDIV1_OUTDIV2(3) | SIM_CLKDIV1_OUTDIV4(3);
431 #error "Error, F_CPU must be 96000000, 48000000, or 24000000"
433 // switch to PLL as clock source, FLL input = 16 MHz / 512
434 MCG_C1 = MCG_C1_CLKS(0) | MCG_C1_FRDIV(4);
435 // wait for PLL clock to be used
436 while ((MCG_S & MCG_S_CLKST_MASK) != MCG_S_CLKST(3)) ;
437 // now we're in PEE mode
438 // configure USB for 48 MHz clock
439 SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(1); // USB = 96 MHz PLL / 2
440 // USB uses PLL clock, trace is CPU clock, CLKOUT=OSCERCLK0
441 SIM_SOPT2 = SIM_SOPT2_USBSRC | SIM_SOPT2_PLLFLLSEL | SIM_SOPT2_TRACECLKSEL | SIM_SOPT2_CLKOUTSEL(6);
443 // initialize the SysTick counter
444 SYST_RVR = (F_CPU / 1000) - 1;
445 SYST_CSR = SYST_CSR_CLKSOURCE | SYST_CSR_TICKINT | SYST_CSR_ENABLE;
450 //_init_Teensyduino_internal_(); XXX HaaTa - Why is this here? Perhaps fixed in a new version of the API?
451 //if (RTC_SR & RTC_SR_TIF) rtc_set(TIME_T); XXX HaaTa - We don't care about the rtc
456 for (ptr = &__init_array_start; ptr < &__init_array_end; ptr++) {
465 // TODO: is this needed for c++ and where does it come from?
472 char *__brkval = (char *)&_ebss;
474 void * _sbrk(int incr)
476 //static char *heap_end = (char *)&_ebss;
477 //char *prev = heap_end;
480 char *prev = __brkval;
485 __attribute__((weak))
486 int _read(int file, char *ptr, int len)
491 /* moved to Print.cpp, to support Print::printf()
492 __attribute__((weak))
493 int _write(int file, char *ptr, int len)
499 __attribute__((weak))
505 #include <sys/stat.h>
507 __attribute__((weak))
508 int _fstat(int fd, struct stat *st)
510 st->st_mode = S_IFCHR;
514 __attribute__((weak))
520 __attribute__((weak))
521 int _lseek(int fd, long long offset, int whence)
526 __attribute__((weak))
527 void _exit(int status)
532 __attribute__((weak))
533 void __cxa_pure_virtual()
538 __attribute__((weak))
539 int __cxa_guard_acquire (int *g)
544 __attribute__((weak))
545 void __cxa_guard_release(int *g)
549 int nvic_execution_priority(void)
552 uint32_t primask, faultmask, basepri, ipsr;
554 // full algorithm in ARM DDI0403D, page B1-639
555 // this isn't quite complete, but hopefully good enough
556 asm volatile("mrs %0, faultmask\n" : "=r" (faultmask)::);
557 if (faultmask) return -1;
558 asm volatile("mrs %0, primask\n" : "=r" (primask)::);
559 if (primask) return 0;
560 asm volatile("mrs %0, ipsr\n" : "=r" (ipsr)::);
562 if (ipsr < 16) priority = 0; // could be non-zero
563 else priority = NVIC_GET_PRIORITY(ipsr - 16);
565 asm volatile("mrs %0, basepri\n" : "=r" (basepri)::);
566 if (basepri > 0 && basepri < priority) priority = basepri;