Maria Christopoulou

Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

5 years, 7 months ago.

LPC1768 & AD9850 DDS distorted signal

Hello,

I am using the LPC1768 to control an AD9850 DDS module (indicative module http://bit.do/eQYWY), with the program https://os.mbed.com/users/alan_matheson/code/AD9850/. However, the output DDS signal is severely distorted.

The connections between the LPC1768 and AD9850 are:

AD9850LPC1768
W_CLKp7
FU_UDp8
DATAp5
RESETp15

I use an external power supply for the DDS module and I have tried both 3.3V and 5V without any result.

The LPC1768 is powered by the USB connector.

For reference, I measured the voltage of the connected mbed digital output pins at around 2.3V. Other unconnected digital pins also have the same voltage.

Please note that the same AD9850 module is working properly when controlled by an Arduino Nano.

Is there any suggestion on how to resolve this issue?

Thank you,

SV1PLE

1 Answer

Wim Huiskamp
5 years, 7 months ago.

I have not used the AD9850 DDS before, but since you have an external powersupply for the AD9850 you should make sure there is a common GND between the mbed and the device module.

Accepted Answer

I connected the VU and GND pins of the LPC1768 to the ADS9850 module (and removed the external power supply) and it is working properly.

Thank you.

posted by Maria Christopoulou 30 Apr 2019