mirror of
https://github.com/rfivet/stm32bringup.git
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147 lines
4.0 KiB
HTML
147 lines
4.0 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>2.2 Another Day, Another Board</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>2.2 Another Day, Another Board</h1>
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As I switched to a new board, I need to check that the code I wrote so
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far is still working as expected. Unfortunately the user LED on the new
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board is wired differently than the first one.
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<h2>Board Schematics</h2>
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<img src="img/22_ledv200.png">
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<p>
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The new board uses <b>PA4</b> to turn the LED ON when <b>high</b>. Also, by
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taking off a jumper, <b>PA4</b> can be used for other purposes.
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<p>
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The first board uses <b>PB1</b> to turn the LED ON when <b>low</b> as I have
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seen previously <a href="14_ledon.html">here</a>.
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<p>
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I can adapt the code by adding the base address of <b>GPIOA</b> and
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shifting pin location accordingly, but this type of variations is so
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common that I want to make sure adaptations can be done easily without
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errors.
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<h2>Board Description</h2>
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I want to be able to capture the board variations through simple definitions:
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<p>
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For the new board:
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<pre>
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#define LED_IOP A
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#define LED_PIN 4
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#define LED_ON 1
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</pre>
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And for the vcc-gnd board:
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<pre>
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#define LED_IOP B
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#define LED_PIN 1
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#define LED_ON 0
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</pre>
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<h2>Implementation</h2>
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I make a copy of <b>init.c</b> into <b>board.c</b> and rework the preprocessor
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macroes.
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<p>
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As I have several GPIO peripheral GPIOA .. GPIOF, I switch notation,
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instead of writing, say, <code>GPIOA_MODER</code>, I will write either
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<code>GPIOA[ MODER]</code> or <code>GPIO( A)[ MODER]</code>. This way I could
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refer directly to <code>GPIO( LED_IOP)[ MODER]</code>.
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<p>
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I use conditional compilation based on <code>LED_ON</code>. If
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<code>LED_ON</code> is high, I need an extra step during initialization
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compare to <code>LED_ON</code> low. On the other hand, if <code>LED_ON</code>
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is undefined, the code would be removed for a board that doesn’t have a user
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LED.
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<pre>
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#define SYSTICK ((volatile long *) 0xE000E010)
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#define SYSTICK_CSR SYSTICK[ 0]
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#define SYSTICK_RVR SYSTICK[ 1]
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#define SYSTICK_CVR SYSTICK[ 2]
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#define CAT( a, b) a##b
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#define HEXA( a) CAT( 0x, a)
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#define RCC ((volatile long *) 0x40021000)
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#define RCC_AHBENR RCC[ 5]
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#define RCC_AHBENR_IOP( h) (1 << (17 + HEXA( h) - 0xA))
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#define GPIOA ((volatile long *) 0x48000000)
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#define GPIOB ((volatile long *) 0x48000400)
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#define GPIO( x) CAT( GPIO, x)
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#define MODER 0
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#define ODR 5
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/* user LED ON when PA4 is high */
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#define LED_IOP A
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#define LED_PIN 4
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#define LED_ON 1
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void SysTick_Handler( void) {
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#ifdef LED_ON
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GPIO( LED_IOP)[ ODR] ^= 1 << LED_PIN ; /* Toggle User LED */
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#endif
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}
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int init( void) {
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/* By default SYSCLK == HSI [8MHZ] */
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/* SYSTICK */
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SYSTICK_RVR = 1000000 - 1 ; /* HBA / 8 */
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SYSTICK_CVR = 0 ;
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SYSTICK_CSR = 3 ; /* HBA / 8, Interrupt ON, Enable */
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/* SysTick_Handler will execute every 1s from now on */
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#ifdef LED_ON
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/* User LED ON */
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RCC_AHBENR |= RCC_AHBENR_IOP( LED_IOP) ; /* Enable IOPx periph */
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GPIO( LED_IOP)[ MODER] |= 1 << (LED_PIN * 2) ; /* LED_IO Output [01],
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** over default 00 */
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/* OTYPER Push-Pull by default */
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/* Pxn output default LOW at reset */
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# if LED_ON
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SysTick_Handler() ;
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# endif
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#endif
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return 0 ;
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}
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</pre>
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<h2>Build and Test</h2>
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I just need to add the <code>SRCS</code> definition in <b>Makefile</b>.
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<pre>SRCS = startup.c board.c success.c</pre>
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and build.
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<pre>
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$ make
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f030f4.elf
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text data bss dec hex filename
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224 0 0 224 e0 f030f4.elf
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f030f4.hex
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f030f4.bin
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</pre>
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Once I have flashed the board with this new binary, I put back the BOOT0
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jumper and press reset. This board user LED is red. 😎
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<h2>Checkpoint</h2>
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I made sure the code I have evolved so far works on the board with the
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serial connection.
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<p>
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<a href="23_hello.html">Next</a>, I will do some serial transmission.
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<hr>© 2020-2024 Renaud Fivet
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</body>
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</html>
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