EOC ADC INTERRUPT

[gdiez]

Posted on August 31, 2010 at 09:51

EOC ADC INTERRUPT

[lipin]

Posted on May 17, 2011 at 14:04

Continuousmode off means there is one sampling & conversion. So it enters ISR andthen stops u need to trigger ADC once again by usingADC_SoftwareStartConvCmd(ADC1, ENABLE); .

Continuousmode on it triggers interrupt on each (group) conversion done. Conversions are made in infinite row.Going more deeply according that you are using 72Mhz clock your ADC clock is:

RCC_ADCCLKConfig(RCC_PCLK2_Div8);

72Mhz / 8 =9Mhz

totalconversion cycles = 1,5 (ADC_SampleTime_1Cycles5) + 12,5 cycles

totalconversion time = 14 * 1/9Mhz = 1,(5) us

So each1,5us you have new value and EOC flag is set. More or less its very short timeand you need to do all your math in this time otherwise next eoc flag is setand may not enter main loop at all. Let’s mention that interrupt latency is 12cycles.

Do youreally need that frequent short time sampling? I bet you want short timesampling but not that frequent than use that continuous mode for sake of simplicityand additional timer to read values. Don’t use EOC flag.

That is theway I see it i might be wrong just starting with stm32.

[gdiez]

Posted on May 17, 2011 at 14:04

My only requeriments are the follow:

- ADC Conversion time =1uS- 20KHz conversion frecuency I have the configuration:XTAL=8MHzHCLK=56MHZ RCC_PLLConfig(RCC_PLLSource_HSE_Div1,RCC_PLLMul_7);APB2= 56MHz RCC_PCLK2Config(RCC_HCLK_Div1);ADCCLK=14MHz RCC_ADCCLKConfig(RCC_PCLK2_Div4);1 Regular channel 1.5 cycles  ADC_RegularChannelConfig(ADC1, ADC_Channel_15, 1, ADC_SampleTime_1Cycles5); 

totalconversion time = 14 * 1/14Mhz = 1us

My sysclk is 56MHz so i think that one clock cycle is 17,85nS more or less, so I think that have enough time to leave the ISR

[lipin]

Posted on May 17, 2011 at 14:04

It's still only 56 cycles but you should be able toquit isr and jump to main loop. Did you set a trap in main loop to check if itsreally not going into there?.  Also try increasing conversion time tocheck if its not really I am to slow in ISR problem.

If you want behavior like in diagram above.

1.

Configure ADC to continuousmode off

2.

Start periodic 20kHz timer

3.

On timer update event start manually conversion ADC_RegularChannelConfig(ADC1,ADC_Channel_15, 1, ADC_SampleTime_1Cycles5);

4.

Wait for conversion by using EOC ISR

5.

When done (ISRevent) setup output compare registers to get desired pulses shape.

Regards

Thomas

[gdiez]

Posted on May 17, 2011 at 14:04

Thks Litom:

I´ve just post the same question in another post hehehe. I will try it and I will tell you. Thks for the help dude

[gdiez]

Posted on May 17, 2011 at 14:04 The original post was too long to process during our migration. Please click on the provided URL to read the original post. https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I6WP&d=%2Fa%2F0X0000000bpp%2F4CVByy4Rhx0LO1RD2iySxXvk18ZW0lVJk8kYuRVTGDg&asPdf=false

[lipin]

Posted on May 17, 2011 at 14:04

Now I see that beginning is just initial condition.

1.

Configure ADC to continuousmode off

2.

Start periodic 20kHz timer

3.

Setup compare registers to trigger interrupt close to end of timer periodand start adc conversion.

4.

On timer updateevent or EOC read analog value and do whatever you want with this probablysetup another compare register to get desired pulse shape.

Even more easy if you don’t need sampling in exactperiods of time. Run ADC in continuous mode forget about EOC flag and readvalue at the beginning of timer update event.

First scenario is also not time accurate too becauseyou need to fire up conversion. As for timers I know there can be made hardwaresynchronization and I bet ADC is able to be externally triggered read docs ifyou need this kind of accuracy.

Regards

Thomas