In this case it turned out to be hardware issue on the peripheral explorer side because of an incorrect schematic diagram. This is prevalent with all TI C2000 peripheral explorers.
The schematic for the Peripheral Explorer R5 shows that the USB-SCI path as:
-GPIO-28 -> USB_SCI_RX -> RX
-GPIO-29 -> USB_SCI_TX -> TX
However, it should be:
-GPIO-28 -> USB_SCI_RX -> TX
-GPIO-29 -> USB_SCI_TX -> RX
You can rework the board by cutting these traces and adding some wires to make the correct connections. Please see the corrected schematics attached with the article.
Texas Instruments have logged this as a hardware bug, however, since the board is relatively stable, it may be a while before a revision occurs.
Please refer this link from Texas instrument's forum describing this issue:
In addition, check your hardware connections along with the settings made on the software side such as baud rate and clock frequency which can also cause similar errors. These are general debugging steps for external mode failures.
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