I'm trying to get Arduino to control DS1801+ digital potentiometer. Datasheet available here: hxxp://datasheets.maxim-ic.com/en/ds/DS1801.pdf . The IC SPI implementation is very straight forward, just need to send 2 bytes in LSB order to set the pot to the desired values. I downclocked the SPI on Arduino to the lowest possible freq (IC supports up to 10Mhz) so it is not an issue here. So, now I'm only able to successfully send about 6 to 10 2 byte commands to the chip and then Arduino communication is broken. I have the Diecimila version with the LED (Prototype Limited Edition) and I have read about other people having trouble with NG version with LED. Could it be an issue here? Actually I can see the LED blinking when the data is being sent. I measured voltage on PIN 13 while the LED is ON and it's 5V. Maybe it's just an issue when the pin is in the SPI CLOCK mode? This is just a part of bigger project and it's a huge show stopper for me. Any help will be appreciated.