N18 Display with Spider II and Cellular

I am finishing up a project for a customer that uses a Spider II with Ethernet and the GHI Cellular modem. I am communicating with a web service using the SIM900’s build in TCP/IP stack. I am not using PPP because I am collecting data using the Spider II’s built in Ethernet. (It is my understanding that .NET mf only supports a single network interface.)

I decided to add an N18 display to show some status information from the Spider. It seems that adding the display has caused more modem communication errors and failed communication attempts with the web service.

When the SPI port is transmitting does it block the UART port from receiving data or interrupts from servicing the UART? I have tried to limit the N18 updates and schedule them around modem communications and that seems to have helped some.

Would using the Spider II’s built in graphics controller with a different display be more efficient?

Any thoughts would be appreciated. Thanks!

Everything in netmf blocks everything else (almost). Try to update only what is necessary instead of updating the whole screen.

@ Gus - That is kind of what I figured. Would using a different display and the internal graphics controller of the Spider be more efficient and block less? I am just guessing, but I would assume it would be since it is using shared memory and the controller handles the actual transfer to the display all in hardware without software control.

Using the internal display would almost not use any resources. The internal hardware does everything without the need for any processor time.

could adding the display introduced a power issue?

@ Mike - I don’t think it was with the N18. There seemed to be more messages garbled or missing characters. But I wouldn’t rule it out completely.
Now the CP7 display caused power issues. The modem would just shutdown. I added a larger 5v supply and it has been running with the CP7 for the last 8 hours. I will circle back with the N18 and larger supply and see if there is any difference. Since it uses only 3.3vdc and not 5vdc I suspect there won’t be much difference. I really think the SPI transfers to the display blocked for to long and caused characters to get dropped from the UART.