Software Serial/UART

[mayursavaj]

Hi,

We are using MK22Fx512 controller of Cortex-M4 series.

I want to use ADC (Pin 15/16/17) as UART-Rx or UART Tx pin as UART Rx because I don't have any UART pin left.

Will anyone suggest me how I will go about it?

Thanks in advance.

[egoodii]

You can certainly implement a 'timer-banged' UART, ala' AN2637.

Reception can use virtually any GPIO -- set a falling-edge trigger to grab the leading edge of the 'start bit', then set a timer for 'somewhat less' than 1/2 bit-time (to compensate for interrupt-response on this, and the subsequent bit-interrupt), thence on that interrupt re-sample 'start' and if valid set 9 more 'full bit' timer-interrupts in succession to sample the input pin to build up the byte, and end by checking 'stop'.  Variations in interrupt-response-time WILL affect the 'quality' of the 'center bit sampling'.

Sending is 'easier and better timed', but requires the use of a timer-output-pin.  For each bit to send, you just set the 'software triggered' output mode, at the bit-width, and on each interrupt you set the NEXT 'state to set at timer expiration' per the next output-bit value.  THIS interrupt-response time is 'relaxed' and only HAS to respond in less than a bit-time.

[mjbcswitzerland]

Earl

The MK22Fx512 is available in a number of packages and as far as I can tell (without being 100% sure though) the pins 15, 16 and 17 referred to are probably on a 64 pin part where they are exclusively ADC (no GPIO function).

Mayur - could you be more specific as to the part number (specifically the pin-count) and which pins are actually being referred to?

Regards

Mark

[mayursavaj]

Hi Mark,

I am using MK22FX512VLL12 of kinetic K series. It have 100 pin package.

Pin No 15, 16 and 17 is dedicated to exclusively ADC.

Can i use this pin as UART Rx? if yes than How?

I have one more pin left UART Tx. Can i use UART-Tx as UART-Rx? if yes than How.

Please give your feedback.

Thanks.

[Hui_Ma · Accepted solution]

Hi,

For pin No. 15, 16 and 17 only with ADC function, there is no way to using software UART with those pins.

For K22 UART  supports Single-wire operation mode, the UART TX could be used as UART transmit and receive pin in a half-duplex working mode.

Please check below picture for the detailed info:

Wish it helps.

Have a great day,
Ma Hui

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[mayursavaj]

Thanks Hui Ma,