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90 lines
3.0 KiB
HTML
90 lines
3.0 KiB
HTML
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>2.1 UART Validation</title>
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<link type="text/css" rel="stylesheet" href="style.css">
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</head>
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<body>
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<h1>2.1 UART Validation</h1>
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Before I start writing some code that communicates over the Universal
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Synchronous Asynchronous Receiver Transmitter (<b>USART</b>) peripheral, I need
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to validate that I have working hardware and software tools.
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<h2>Board Connectivity</h2>
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Even if the peripheral is capable of doing synchronous communication
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(that’s the S in USART), asynchronous communication (that’s the A) which
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only needs 3 wires (GND, TX, RX, (no clock)) is usually what is needed
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in non specialized cases.
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<p>
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Boards sold online often have dedicated pre-soldered pins for UART
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connectivity similar to what I have seen before for the SWD interface.
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The VCC-GND board I used previously doesn’t have such dedicated pins but the
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functionality is wired on the pins PA9 (<b>TX</b>) and PA10 (<b>RX</b>).
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<p>
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I will use a board with dedicated pins (GND, TX, RX, VCC 3.3V). Board
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specifications can be found
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<a href="https://stm32-base.org/boards/STM32F030F4P6-STM32F030F4-V2.00">
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here</a>.
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<p>
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<img alt="STM32F030F4-V2.00" src="img/21_boardv200.png">
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<h2>USB to UART adapter</h2>
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An adapter is needed to connect to a PC. Either due to difference in
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voltage (<b>RS232</b>) or serial protocol (<b>USB</b>). Pins PA9 and PA10 are
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5V tolerant, so you could interface an Arduino Uno to a STM32 board to use
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it as a USB to serial adapter if you happen to have a spare Arduino Uno.
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<p>
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I use an adapter based on <b>Silicon Labs CP2102</b> chipset.
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Windows has USB driver available for Silicon Labs CP210x chipset family.
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The adapter enumerates as <b>COM4</b> on my Windows PC.
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<p>
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I connect the adapter to the board to provide 3.3V and make sure to cross
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RX and TX wires (STM32 RX <-> Adapter TX, STM32 TX <-> Adapter RX).
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<h2>STM32 Cube Programmer UART connection</h2>
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So far I have been using the ST-Link interface with STM32 Cube
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Programmer to flash and debug. The application also support the UART
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interface.
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<h2>Embedded Boot Loader</h2>
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A reset of the board while jumper <b>BOOT0</b> is removed will select the
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System memory instead of the flash memory for execution. This is where
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the serial flash loader protocol is implemented on chipset side.
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<p>
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<img alt="BOOT0 Jumper Selection" src="img/21_boot0.png">
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<h2>Testing</h2>
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The checklist goes like this:
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<ul>
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<li> Board connected to USB adapter
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<li> USB driver installed on Windows PC
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<li> USB adapter plugged in and enumerates as a COM port
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<li> STM32 Cube Programmer list the COM port in device selection menu
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<li> BOOT0 jumper removed and board reset to start the embedded flash
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loader.
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<li> Board flash memory can be erased, written or read with the programmer.
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</ul>
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<h2>Checkpoint</h2>
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I have now working hardware and software that communicate through the
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serial link.
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<p>
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<a href="22_board.html">Next</a>, I will make sure the code I wrote so far is
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working on the new board.
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<hr>© 2020-2024 Renaud Fivet
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</body>
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</html>
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