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I'm encountering problems flashing my LPCxpresso1769 with FlashMagic.

I had previously been able to get it to work using a USB to UART lead (TTL-234X-3V3) and powering the device externally (i.e. not via the USB debug probe).

I've since lost the USB to UART lead so have tried using a USB to RS232 instead (https://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_USB_RS232_CABLES.pdf). Is this the reason for my problems? Do I need to use UART?

19172281
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1 Answers1

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Both are USB UART cables, but you need one with 3.3V TTL voltage levels, the microcontroller cannot tolerate RS232 voltage levels and they have inverted polarity as well, so RS232 cables would be incompatible and may break the MCU with overvoltage.

Justme
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  • Yes, I read up on RS232, and noticed that the voltage levels were not TTL. Is is safe to assume that I've damaged my board? – 19172281 Jan 04 '20 at 17:26
  • You can't assume anything unless you have tested it. It may be just fine or may be broken. MCUs do have protection diodes, and the overvoltage/overcurrent situation magnitude depends on how strong RS232 drivers the cable had, and also time of duration for it. – Justme Jan 04 '20 at 17:29