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AnsweredHot!UART6 line (pin 78 of 144) doesn't go above 1V

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snellr314
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2020/05/08 04:57:12 (permalink)
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UART6 line (pin 78 of 144) doesn't go above 1V

Hello,
 
I have a Harmony v3 generated project for PIC32MZ2048EFM144 trying to communicate over UART6 with pin 78 (F3) as TX and pin 79 (F2) as RX. The TX line is at 1V steady and then toggles to ground when I am transmitting, but it never goes above 1V, before during or after. I even cut my trace so that there was nothing else connected to the pin and it still never got above 1V. I pulled out a second board (both professionally populated) and it had the same issue.
 
Supposedly, those pins can be reversed, so I put the TX on pin 79 and it rose to 3V and transmitted fine. But pin 78, now on RX, still only rose to 1V.
 
Is there an issue with pin 78?
 

    /* PORTF Initialization (pin 78 TX) */
    LATF = 0x0; /* Initial Latch Value */
    TRISFCLR = 0x13; /* Direction Control */
    ANSELFCLR = 0x3000; /* Digital Mode Enable */
    CNPDFSET = 00; /* Pull-Down Enable */

 
post edited by snellr314 - 2020/05/08 07:21:52
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LostInSpace
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Re: UART6 line (pin 78 of 144) doesn't go above 1V 2020/05/22 21:29:11 (permalink) ☼ Best Answerby snellr314 2020/05/25 06:00:07
5 (3)
Unfortunately you have fallen into the RF3 Pin Black Hole of non-functionality. The USB Module must be powered to use RF3 as a digital IO. Full details here,
https://www.microchip.com/forums/m949914.aspx
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snellr314
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Re: UART6 line (pin 78 of 144) doesn't go above 1V 2020/05/25 06:00:54 (permalink)
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Thank you, LostInSpace. I'll find a different gpio to use, but I'm glad to know that I didn't just have a weird solder bridge or messed up project configuration. I did test and validated your conclusion.
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