How to just use TTL puart in TAG3 without through USB?

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Anonymous
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I have read MMP920737TAG03-HWUM100-R.pdf, I know that TAG3 have a USB port and it can simulate two com ports on PC, one is HCI, the other is puart.

Through USB, HCI and PUART work fine. But I have an idea that use PUART TX and RX pins which are TTL level. After checking the MMP920737TAG03-HWUM100-R.pdf, on GPIO header, I found that J7 Pin 5 and J8 Pin 1 are PUART TX and RX. I also found that I should switch SW4 pos5~6 to OFF to make PUART disconnect with USB module. Then, I use my TTL2USB cable to connect with J7 pin5 and J8 pin 1, but I can't get anything through tera term4.83. But after switch SW4 pos5~6 to ON, I can data output and input work normal through USB port.

So, what extra action should be taken if I want to use PUART pin32 and pin33 which do not connect with USB port?

BTW, my TTL2USB cable is this one: http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm

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1 Solution
Anonymous
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Resolved this issue.

I initial PUART_RX as pin25 which should be pin32.

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