NMI-based hw_timer implementation in RTOS SDK

[rhaenel]

Hi,

I have some pulse shaping applications that are very sensitive to correct timing (in the 100ns-range).

After some experiments I found that even though I disabled interrupts during my function, I still get interrupted, and I assume thats the NMI which I cannot turn off.

However someone pointed me towards the hw_timer implementation where I can actually execute code from within the NMI, and that means that another NMI cannot interrupt me - great!

Unfortunately I just found out that the hw_timer stuff with NMI doesn't seem exist in the RTOS SDK. Stuff is missing from the header files, I could add that, but then it seems that some internal stuff is missing from libmain.a (NmiTimSetFunc) and that's a binary blob I don't have access to.

So the question is: is there any way to use an NMI-based hw_timer in the RTOS SDK? Or any other way to capture and/or disable the NMI in the RTOS SDK? I only need uninterruptible control for a very short period (~ 10 microseconds).

Greetings,
Roland

[ESP_Faye]

Hi,

I only need uninterruptible control for a very short period (~ 10 microseconds).

Do you mean that this 10 microseconds can not be interrupt by NMI either ?

1. Call wifi_set_opmode(NULL_MODE); first, then enter critical state. These will allow an uninterruptible control for about 1.5 seconds.

2. Call wifi_set_opmode to set a normal Wi-Fi mode, then enter critical state. Only Wi-Fi NMI can interrupt task or other interrupts.

Thanks for your interest in Espressif Systems and ESP8266 !

[rhaenel]

Thanks.

Calling wifi_set_opmode(NULL_MODE); would kill the current WiFi connection, correct? If I enable station mode after the time critical stuff (10us), this will trigger WiFi connect including DHCP etc. again, correct?

Greetings,
Roland

[eriksl]

AFAIK pwm also uses nmi, maybe other software emulated subsystems as well.

[dkinzer]

AFAIK pwm also uses nmi,

I haven't seen a PWM example using NMI. The PWM code in the v0.9.5 SDK IOT_demo directory uses a regular interrupt. Earlier versions of the SDK (e.g. v0.6) had PWM example code that used os_timer_setfn(). Do you have a URL for PWM code that uses NMI?

[eriksl]

I am talking of the pwm implementation IN the sdk, not an example. Current sdk is 1.2.0, why would you use 0.9.5? See include/pwm.h.

[dkinzer]

Current sdk is 1.2.0, why would you use 0.9.5? See include/pwm.h.

I am using v1.2.0. I was referring to the example pwm.c code found in the earlier versions of the SDK that is not present in 1.2.0.

[eriksl]

I was merely trying to explain that at least one sdk subsystem is using NMI interrupts, namely pwm, maybe others too. These might interfere with your tight timing requirements.