Target reboots during driver debug

Hello tns1,

Trace is available without an additional license from FS2 for 16 frames of trace data. Several instructions are packed into the bits of each trace frame, resulting in a few dozen instructions worth of trace from these 16 trace buffers. You also get 2 data breakpoints and 2 instruction breakpoints without an additional license. You can use these breakpoints with an event of turning on or off trace, thereby targeting those few dozen instructions worth of trace information right where you want them.

I think your guess of a wild pointer is probably accurate. The most common problem I have seen with ethernet drivers and the lwIP stack is a stack overflow. Such an overflow may be causing a jump to zero, and if your reset address is located at zero, this could make a symptom of stack overflow look like a reset of the board. This is common because any task which uses sockets must be created by the lwIP sys_thread_new instead of OSTaskCreate, and sys_thread_new only allocates 2048 bytes per task. Any call to an RTL function, including printf, consumes almost 1000 bytes of stack space, which is half of your task stack right there. One customer who I helped had identical symptoms, but had all of his printf statements wrapped with a# define for DEBUGGING. After turning off hi DEBUGGING macro, and therefore eliminating all of his calls to printf from with any tasks, incluing those using sockets, his ethernet driver worked fine.

You can modify the stack space created for each sys_thread_new call by modifying this function's definition. This source code is located in the Nios II Device Drivers project, under the lwip component.

You can use FS2 data breakpoints to watch for stack overflow. Step into the sys_thread_new function calls, which calls OSTaskCreate, in order to find the address which is passed to the OSTaskCreate calls as the stack address parameter. Then set your FS2 data breakpoints to watch for any writes to the end of that stack, and you can catch your stack overflow.

By the way, the FS2 interface has been improved for Nios version 1.01, and is well worth downloading, installing, and recreating your projects under the new version (remember to uninstall Nios 1.0 first).