2021-11-08

  • zy09 reading assigned. Target done by Wednesday.

  • zy10 reading also assigned. May as well start.

1. UART Serial communication

  • Universal Asynchronous Receiver-Transmitter

https://www.analog.com/en/analog-dialogue/articles/uart-a-hardware-communication-protocol.html

https://en.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter

Maxim Integrated AN2141 - Determining Clock Accuracy Requirements for UART Communications

The protocol is pretty simple. One. Bit. At. A. Time.

  1. Start bit. Mark -> Space transition (usually 1->0)

    • hold low for 1 bit time

  2. Data bits

    • least-significant bit first!

    • N data bits total (5…​?)

      • 8-bits is common

      • 7-bits is found in oldskool ASCII systems

  3. Parity bit?

    • none

    • even (such that there is an even number of 1’s)

    • odd (…​ to make an odd number of 1’s)

  4. Stop bit

  5. Second stop bit?

    1. optional, rare

  6. (back to idle)

    • usually back to Mark level (1)

uart bits

ASCII is an encoding, it maps a group of 7-bits (0b0xxx xxxx)to a symbolic meaning

2. Serial terminal

Supplies:

  • PC with terminal program

  • MSP430 LaunchPad, loaded with msp4th

  • AD2

Watch the protocol in real time.

Open MobaXterm

Session -> Serial

mobaxterm serial

Ensure the MSP430 is attached.

Then, run the session and select a COM Port:

mobaxterm serial port

You should see a blank black screen.

Press RST on your LaunchPad.

You should see

msp4th!

>

Forth code:

https://drive.google.com/file/d/1Ovn8UbG7c3-Y2zkLwbYdORB3EE-lZllb/view?usp=sharing

Paste into Notepad++:

\ word definitions for accessing MSP430 GPIO registers
\ builds "ledN" to

\ set language to Forth for highlighting


\\\\\\\\\\\\\\\\
\ setup some "constant"s
\\\\\\\\\\\\\\\\

\ P1OUT register address
( -- &P1OUT )
: P1OUT 0x0200 0x02 + ;

\ P9OUT register address
( -- &P9OUT )
: P9OUT 0x0280 0x02 + ;



\\\\\\\\\\\\\\\\
\ utility functions (words in Forth)
\\\\\\\\\\\\\\\\

\ clear bits at memory address
( mask addr -- )
: bic tuck @ swap ~ & swap ! ;

\ set bits at memory address
( mask addr -- )
: bis tuck @ swap | swap ! ;


\\\\\\\\\\\\\\\\
\ "application" words
\\\\\\\\\\\\\\\\


\ set an LED on/off
( bool -- )
: led1 push0 == if 0x01 P1OUT bic else 0x01 P1OUT bis then ;

\ alternate defintion style, doesn't repeat the port/pin info
: led1 push0 == 0x01 P1OUT 2 roll if bic else bis then ;

\ set led2 to bool
( bool -- )
: led2 push0 == 0x80 P9OUT 2 roll if bic else bis then ;


\ example: turn LED1 on then off
1 led1
0 led1

https://documentation.help/PuTTY/config-crlf.html

3. msp4th

Download and unzip msp4th-launchpad.zip

  • Create a new Code Composer Studio project.

  • Replace/paste main.c

  • Add the other two files to the project.

  • Build and flash

Default configuration uses the built-in LaunchPad UART at 9600 8N1:

  • 9600 baud

  • 8-bit transfers

  • No parity

  • One stop bit

https://www.embedded.com/catching-errors-early-with-compile-time-assertions/

https://www.forth.com/starting-forth/1-forth-stacks-dictionary/

https://www.forth.com/starting-forth/4-conditional-if-then-statements/

0 echo

: P1OUT 0x0200 0x02 + ;  ( -- &P1OUT )
: P9OUT 0x0280 0x02 + ;  ( -- &P9OUT )
: bic tuck @ swap ~ & swap ! ;  ( mask addr -- ) \ clear bits at memory address
: bis tuck @ swap | swap ! ;  ( mask addr -- ) \ set bits at memory address

//
: led1 push0 == if
        0x01 P1OUT bic
    else
        0x01 P1OUT bis
    then ;

: led1 push0 == 0x01 P1OUT 2 roll
    if bic
    else bis
    then ;

: led2 push0 == 0x80 P9OUT 2 roll
    if bic
    else bis
    then ;

1 echo

https://dev.ti.com/tirex/explore/node?devtools=MSP-EXP430FR6989&node=AOpNP3B6FOXx.PNv5ZDeJQIOGqZriLATEST

msp430fr69xx_euscia0_uart_03.c