Slow ADC conversion on Xpresso board

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by andrejvrecer on Sun Nov 16 07:07:41 MST 2014

I have some issues with ADC conversation. I have used example code from lpcopen_2_08c_lpcxpresso_nxp_lpcxpresso_1549.zip on ADC src.
I have added USB VCom code to my project to use as debug port.

Have used SysTick to sent out debug every 1s. I use uint32_t counter to count how many ADC measurements on 1 channel (ADC0.1) is made in burst mode on SEQ_A
The number is ONLY 19229 times! I can't get anything close to 2MSamples. Also I used osciloscope to measure time between 2 ADC interrupts and time was around 50us which is around the same as numbers of ADCs in 1 sec.

The same problem I have on ACMP where I wished to measure response time on input pulse. From time I pressed external button to LED change using ACMP interrupt it took around 80-100us !! Is this normal? I need response time on less then 10us. Non filters were used on ACMP (bypass mode).

So at the end my research is showing that my xpresso board is "slow"? I have debug out all clocks and are 72MHz and devider is 1 for perihibal.

What am I doing wrong. I can attach code but at the end is example code from you guys.

Before I have used LPC1347 and ADC measure time was around 20us (now 50+)

I have tried Release and Debug compile...both made the same result. Is LPC1549 slow when some debug chip is connected to it?

Please help me I am out of ideas after 3 days of coding.