Hello Philipp,

Saturday, August 5, 2017, 8:41:42 PM, you wrote:

PS> Yes, you're probably right.

PS> Though I wonder when and how they programmed the firmware. Before or
PS> after soldering?

Most likely before, unless they have some debug header exposed. From
[1]:

> When the hardware and software nears production readiness, it is
> common practice to preprogram flash memory devices prior to
> starting high-volume PCB manufacturing flows for two principal
> reasons. First, firmware loaded onto the device can be used to
> perform basic booting and testing of the PCB during manufacturing
> to check system/module functionality. Second, loading the final
> firmware, operating system (OS), and application code on the flash
> device prior to manufacturing maintains a high-volume
> manufacturing beat rate. To support these usage models, multiple
> vendors provide systems for loading firmware and data into flash
> memory devices prior to the PCB solder flow process.

Modern flash chips don't have issues retaining programmed bits during reflow
soldering as long as the correct temperature profile is observed [2].

[1]: 
http://www.electronicdesign.com/memory/understanding-onboard-flash-programming
[2]: http://dataioinfo.com/LiveImages/26/20/DocumentURL.pdf



-- 
WBR,
 Igor                            mailto:rox...@skynet.be


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