PV198 - UART I
One-chip Controllers
Daniel Dlhopolček, Marek Vrbka, Jan Koniarik, Oldřich Pecák, Tomáš
Rohlínek, Ján Labuda, Jan Horáček, Matúš Škvarla
Faculty of Informatics, Masaryk University
8/2023
Introduction
UART
FRDM-K66F UART
Application
Homework
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Introduction
Intro
Switch the branch to Week_08!
Discussion of HW7
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UART
Embedded communication buses
SPI – Serial Peripheral Interface
I²C – Inter-Integrated Circuit
UART – Universal asynchronous receiver / transmitter
CAN – Controller Area Network
1-Wire
RS-485
RS-232
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UART
UART
UART = Universal Asynchronous Receiver-Transmitter
Serial communication
"Serial port" – old D-SUB 9 connector (UART = RS232 TTL)
Application: intra-board communication
sensors
GPS
bluetooth
modems
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UART
UART Principles
2 wires
1. RX – receive
2. TX – transmit
1 to 1 communication
No master nor slave, just 2 equal
communication participants
Works without clock signal
Requires same UART configuration
for both communicating devices
(baud rate, parity, etc.)
Asynchronous
Full-duplex
Device 1 Device 2
RX
TX
RX
TX
GND GND
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UART
UART Message
BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 BIT 8START
BIT
STOP
BIT
START
BIT ...
1 start bit 8-9 data bits 1-2 stop bits
0-1 parity bits
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UART
UART Settings
Baud rate (typical 9600 baud/s – 115 200 baud/s)
Number of data bits (8–9)
Number of stop bits (1–2)
Parity bit (disabled / odd / even)
Note – Baudrate vs. bitrate
Bitrate = bits per seconds.
Baudrate = symbols per second.
When bus allows more than 2 states (0/1) at one time, bitrate is
higher than baudrate. E.g. bus with 4 voltage levels (2 bits at one
time) with baudrate 1 kBaud/s has bitrate 2 kBits/s.
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FRDM-K66F UART
FRDM-K66F UART
5 UART modules
RS-485 support
Hardware flow control (RTS/CTS)
9-bit UART support
Interrupts
DMA support
TX/RX FIFO
MCUXpresso SDK API Reference Manual – UART driver
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FRDM-K66F UART
USB to UART Bridge CP2102
We use it to connect MCU’s UART to PC.
Specification
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Application
Seminar task I
Create an application that reads data from UART and sends the
data back to PC.
Update your code to rotate received character +2.
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Application
Seminar task I – Step-by-step guide
1. Create an empty FRDM-K66F project.
2. Setup pins routing & peripherals for UART communication.
PTB11 as UART3_TX, PTB10 as UART3_RX
UART3 with 8 bit data, 1 stop bit, no parity, 115200 baudrate
3. Connect “USB to UART bridge” to a board (based on pins
routing).
Connect just RXD, TXD, GND.
Do not forget to swap RX & TX.
4. Connect “USB to UART bridge” to a PC, new COM port appears in
Device Manager in “Ports (COM & LPT)”.
5. Program desired functionality.
MCUXpresso SDK API Reference Manual – UART driver
6. Open terminal application (e.g. PuTTy or Terminal view in
MCUXpresso IDE) and connect to correct COM port with UART
settings configured in MCU. Try programmed functionality.
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Application
Seminar task II
Task II
Write a PC application which communicates with your MCU.
1. Use same MCU program as in Task I.
2. Use Python, use import serial.
In case pyserial is not available:
python.exe -m pip install pyserial
3. Send string to the device.
4. Read "encrypted" string back.
5. Check if device correctly "encrypted" the string.
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Homework
Homework – RGB over UART
On device side you will receive 3 bytes.
These 3 bytes represent RGB values in order RGB.
Your goal is to set RGB LEDs colors according to received values.
Use PWM.
Due to testing, set the Timer Output Frequency in the FTM
peripheral to “262 144 Hz”
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