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Microchip Pic32 exception: ???

Hi. I'm trying to understand the Pic32 (a decade of familiarity with Pic16 and Pic18). I got myself an Ethernet Starter Kit. The demos run, and I have been able to edit them. So I tried to get two stacks working together. I then proceeded merging the TCPIP demo and the USB MSD demo. The latter just looks for a pendrive and when it sees it a simple text file gets written. The TCPIP integrates a basic http webserver. By themselves I'm able to run them. I merged the source files, integrating the USB stack calls in the main loop after the TCPIP stack calls. Fact is the compilation goes through but upon running, code gets stuck. Initialization goes through until the MAC init, at line 238 of ETHPIC32IntMac.c there is this line

if(EthDescriptorsPoolAdd(EMAC_TX_DESCRIPTORS, ETH_DCPT_TYPE_TX, _MacAllocCallback, 0)!=EMAC_TX_DESCRIPTORS)

this one apparently fails and I have no clue why. EMAC_TX_DESCRIPTORS are defines, but ETH_DCPT_TYPE_TX is nowhere to be found, as well as the EthDescriptorsPoolAdd function. Fact is they are nowhere to be found even in the demo project that works!

After that the code falls down to the main exception handler

void _general_exception_handler(unsigned cause, unsigned status) { Nop(); Nop(); }

codes are

cause = 0x10800034 status = 0x00100003

which I can't find anywhere. Now the exception handler description suggests that a read/write operation was issued on a NULL pointer, or that the stack was overflowed.

But the function looks to be asking for memory allocation, and infact it's a calloc that fails. But then even increasing the HEAP size doesn't make it. The project compiles, it runs without getting stuck, but every function calling on the MAC interface fails. As if the pointer is wrong or there is no MAC interface instanced.

I really don't know where to look. Can you suggest me a course of action?

Thanks Claudio

Reply to
Claude
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Have you tried the microchip pic32 forum?

formatting link

Reply to
Rocky
[much elided]

You are *sure* this statement is being compiled in the demo project(s)? If so, then ETH_DCPT_TYPE_TX *is* somewhere -- along with EthDescriptorsPoolAdd(). Look harder. :>

You should be able to examine the stack pointer as well as the stack's contents.

Are either the size or number of elements *0*? Alternatively, are either of these "extraordinarily *big*" values?

You sound like you're just poking the code with a stick instead of trying to *identify* what it is actually doing. IME, that's a terribly inefficient and ineffective debugging technique. :<

Does your IDE allow you to cross-reference symbols? (i.e., to chase down the above)

Do you have a recursive grep(1) available?

Can you *step* through the code to see where it tries to go (then look at the link map to see what is actually *there*)?

The machine does what it is *told*. Figure out what it is being *told* to do and you will have a better insight into why it isn't doing what you *think* it should!

HTH

Reply to
Don Y

status)

cause and status are defined by the MIPS architecture. Google 'MIPS32 architecture for programmers' and look in volume III under the chapter for exceptions. It's useful to look at the address in the EPC - that should be where the fault occurred. In this case it looks like a trap exception.

When an exception happens the software exception handler is in charge of storing off the registers (except cause, status, and EPC), so you need to know how that works to decode the state of the registers and the register save area.

Reply to
Andy

ETH_DCPT_TYPE is defined as 0x2 in: Microchip/MPLAB C32 Suite/pic32-libs/include/peripheral/eth.h

EthDescriptorsPoolAdd is in the application library that links in from the compiler library. It's there somewhere.

Reply to
linnix

Thank you very much, it looks like usefull information. I'll check it.

Claudio

Reply to
Claude

Been there, done that. Those forums are pretty much useless.

Claudio

Reply to
Claude

In article , snipped-for-privacy@here.com says... Thank you DonY, your has been the most usefull post till now.

Will comply...

Yes I should, but I'm a bit unfamiliar with this kind of low level debugging.

It didn't look like it, but I will check again.

If you mean stepping backwards then no. And no grep, there is no OS beneath this, it's purely microcontroller work.

Yes and it jumps. I can follow through to the incriminated calloc I mentioned, then since it's implementation isn't available as source, it steps though some asm garbage I can't comprehend (I never learned asm) and then arrives to the asm equivalent of the exception handler.

Yeah, know it pretty well. Luckily it's not my first project ;)

Claudio

Reply to
Claude

My bad. I'm under windows, I can search whatever file I want. I'm not clear on the recursive grep... Literally no, but anyway what would you want me to search in such a way?

The IDE offers a project-wide text search, so I can look in any explicitely included file. That means though that if a file gets included deep in another file, and not explicitely in the project, the search won't go through it.

Claudio

Reply to
Claude

Did you look at my post? I already did a "find ./Microchip -exec grep ETH_DCPT_TYPE_TX {} ;" on the compiler tree. It's defined as 0x2 in Microchip/MPLAB C32 Suite/pic32-libs/include/peripheral/eth.h

Reply to
linnix

Thanks Linnix, I missed it.

Claudio

Reply to
Claude

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