GPIO act incorrectly when building with GCC

RE: GPIO act incorrectly when building with GCC

Quark — Thu, 30 Mar 2017 14:06:30 GMT

Tried Os option, but even set optimization for size does not make it slower, I still need to add the delay to produce correct clock sequence. FYR

RE: GPIO act incorrectly when building with GCC

Quark — Thu, 30 Mar 2017 13:59:51 GMT

OK, I will try it.

RE: GPIO act incorrectly when building with GCC

Radoslaw Koppel — Thu, 30 Mar 2017 13:48:24 GMT

In our examples GCC is optimised using O3 level that intuitively relates to Level 3 optimisation in Keil. (Whisper:) Use Os instead and compare the compiled codes.

RE: GPIO act incorrectly when building with GCC

Quark — Thu, 30 Mar 2017 13:34:10 GMT

Great, myth busted, thanks for the answer!

RE: GPIO act incorrectly when building with GCC

Radoslaw Koppel — Thu, 30 Mar 2017 13:00:14 GMT

Yes - We was also experiencing this issue writting the libraries. GCC is much more efficient with inlining the code.

RE: GPIO act incorrectly when building with GCC

Quark — Thu, 30 Mar 2017 12:40:10 GMT

I found I can fix the problem by adding some delay (1us will be fine) as below

  for (int i = 0; i < DOUT_LINES; i++) {
        nrf_gpio_pin_write(DS, i == line);
		nrf_delay_us(1);
		nrf_gpio_pin_write(SHCP, HIGH);
		nrf_delay_us(1);
		nrf_gpio_pin_write(SHCP, LOW);
		nrf_delay_us(1);
  }

But why code compiled with Keil does not need this delay? Does it mean GCC compiled code is running more efficiently (faster) than compiled by Keil?