wierd float64_t vs. float32_t

[schef]

Hi, I have wierd experience about using float32_t. This is my test:

When i use operations on float64_t i got:

0.0001s   MAIN:INFO:init_finished
0.0001s   MAIN:INFO:loop
0.5077s   MAIN:INFO:loop //timer interrupt
0.4978s   MAIN:INFO:loop //timer interrupt
0.4970s   MAIN:INFO:loop //timer interrupt

normal timer interrupt which happend every 500ms.

in main i have:

for (;;)
{
  NRF_LOG_INFO("loop\n");
  power_manage();
}

but when i use float32_t i have strange interrupts:

0.0001s   MAIN:INFO:init_finished
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop
0.0001s   MAIN:INFO:loop

Does this have any sense?

I use nrf52 with sdk 12.2.0 i have this code:

#define ARM_MATH_CM4
#include "arm_const_structs.h"
#include "arm_math.h"

and flags

CFLAGS += -mfloat-abi=hard
CFLAGS += -mfpu=fpv4-sp-d16
LDFLAGS += -mfloat-abi=hard
LDFLAGS += -mfpu=fpv4-sp-d16

[RK]

you haven't posted any code so it's impossible to know what it is generating your output

[schef]

I was able to reproduce the error on the example. So i have attached the code. Try to play in sensors/battery_level/battery_ext_level.c function static void convert_battery_ext_level_to_buffer(uint16_t value, uint8_t *buffer) on line 10.

If you change the type from float to double there is no error.

ble_app_hts_float_problem.rar

[schef]

here is a video demonstration asciinema.org/.../bpd6s70capvyrxo07jhtgizjm

[Sigurd]

Hi,

You seem to be running into errata [87] CPU: Unexpected wake from System ON Idle when using FPU. Add the workaround to the power_manage() function, and the problem should be solved:

 void power_manage(void)
{
  NRF_LOG_INFO("power_manage!\r\n");
  #if (__FPU_USED == 1)
  __set_FPSCR(__get_FPSCR() & ~(0x0000009F)); 
  (void) __get_FPSCR();
  NVIC_ClearPendingIRQ(FPU_IRQn);
  #endif
  uint32_t err_code = sd_app_evt_wait();
  APP_ERROR_CHECK(err_code);
}

[schef]

Yes, thank you. That did solve the problem.