We use SCM20260N modules. When releasing devices, we flash TinyCLR v2.2.0.5000 and the application. The application requires an extended heap and an extended deployment. After enabling extended deployment, the module is no longer detected via USB. This problem appeared once a long time ago. But it has recently been repeated on the second device. What is it, how to fix it if possible?
Will complete erase of the device and reflash get it back to life? Was this device working before?
When the LDR pin is pulled low during startup, we can enters to bootloader mode and completely erase it. Then we can flash TinyCLR again and after enabling the extended deployment, everything breaks again. We are mass-producing devices and new modules are installed in them.
Does the tca file work on other modules or just bad on that specific module?
tca file work on all other modules fine.
In addition, the flash of the application has not yet been made.
Flash TinyCLR and App via TinyCLR Config
seems to me the module has bad chip somehow. Could you please do few steps below for investigation
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Try to deploy a different application, just hello world, add some binary files to resource (> 1MB), enable external mem and deployment and deploy that app? does it work?
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If (1) doesn’t work, can you update firmware to latest, and do (1) again? latest firmware we reduced QSPI that may help.
Tell us 1) and 2) result then we will think about next
I can’t enable extended deploymen via TinyCLR Config.
I tried enable it via code in Main() but the result is the same
Can you update latest firmware to see if that help? Just update latest firmware and use the tool to see if you can enable external deployment
I will definitely try, but not today. I’m already at home 
Today I checked the modules again and discovered that I was mistaken - the extend heap does not turn on. Please excuse me. I have adjusted the topic. The behavior is the same as I described.
And one more thing. When I turn it on for the first time, the bootloader does not start, but only when the LDR pin is pulled low during startup.
Could you look at the SDRAM pins, check carefully if any pin doesn’t have good connection?
does this module work before right?
these are new modules
Could you please check if all SDRAM pins have good connection?
I’ll check it under a microscope
We have two modules like this, they work ok until you enable the extended heap.
A simple memory test program shows the extended RAM isn’t working correctly- on one there are just a few bad areas, on the other the whole RAM appears bad.
I bought a couple of replacement RAM chips with the plan to try swapping them when I’m back from travels at the end of next month - not sure how I’ll go about that yet as they are installed on otherwise good custom boards.
I looked and didn’t see anything suspicious
Is there some kind of memory check performed when modules are released?
Yes of course, everything is checked but we are checking everything in your case to see what the problem mighty be.
Looks like the problem is the same as C_Born’s
If SDRAM is bad then it somehow got damaged. I know these chips are sensitive to humidity when they go in reflow ovens, which is why we require baking before soldering. This is just a possibility.