Simple I2C example for STM32F0 family

examples/stm32/f0/other/i2c/Makefile

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+##
+## This file is part of the libopencm3 project.
+##
+## Copyright (C) 2009 Uwe Hermann <[email protected]>
+##
+## This library is free software: you can redistribute it and/or modify
+## it under the terms of the GNU Lesser General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This library is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU Lesser General Public License for more details.
+##
+## You should have received a copy of the GNU Lesser General Public License
+## along with this library.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+BINARY = i2c
+
+LDSCRIPT = ../stm32f030.ld
+
+include ../../Makefile.include

examples/stm32/f0/other/i2c/README.md

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+# README
+
+It's intended for naked STM32F030F4 MCU and I2C flash memory Atmel 24C02. The I2C bus is connected to flash memory Atmel 24C02 (but many other memories will do, consult datasheet) - [http://ww1.microchip.com/downloads/en/devicedoc/doc0180.pdf]
+The application programs bytes 0x01 and 0x02 with values 0x42 and 0x77 respectively, reads the values back and prints them to the serial port.
+
+## Board connections
+
+| Port   | Function   | Description                  |
+| ------ | ---------- | ---------------------------- |
+| `PA2`  | `(USART1)` | Serial output (115200,8,N,1) |
+| `PA9`  | `(SCL)`    | I2C connection               |
+| `PA10` | `(SDA)`    | I2C connection               |
+
+The I2C bus requires pullup resistors (e.g. 4k7), this application uses dirty workaround switching on internal pullups.

examples/stm32/f0/other/i2c/i2c.c

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+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2009 Uwe Hermann <[email protected]>
+ * Copyright (C) 2011 Stephen Caudle <[email protected]>
+ * Modified 2018 by Jiri Bilek <[email protected]>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <errno.h>
+#include <stdio.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/usart.h>
+#include <libopencm3/stm32/i2c.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/cm3/systick.h>
+
+#define USART_TX	GPIO2
+#define I2C_MEMORY_ADDR  0x50
+
+static void systick_setup(int xms);
+static void clock_setup(void);
+void delay(uint32_t time);
+static void usart_setup(void);
+static void i2c_setup(void);
+static void print(const char *s);
+
+volatile uint32_t millis = 0L;  // millis since start of the program
+
+/*
+ * Called when systick fires
+ */
+void sys_tick_handler(void)
+{
+	++millis;
+}
+
+/*
+ * Set up timer to fire every x milliseconds
+ */
+static void systick_setup(int xms)
+{
+	systick_set_clocksource(STK_CSR_CLKSOURCE_EXT);
+	STK_CVR = 0;
+
+	systick_set_reload((rcc_ahb_frequency / 8 / 1000 * xms) - 1);
+	systick_counter_enable();
+	systick_interrupt_enable();
+}
+
+/*
+ * Set STM32 to clock by 48 MHz from HSI oscillator
+ */
+static void clock_setup(void)
+{
+	rcc_clock_setup_in_hsi_out_48mhz();
+}
+
+/*
+ *  Delay in milliseconds
+ */
+void delay(uint32_t time)
+{
+	uint32_t old_millis = millis;
+
+	while (millis - old_millis < time)
+		;
+}
+
+/*
+ * Set up USART1: TX on USART_TX(PA2 - alternate pin), RX not used
+ * 115200 baud, 8N1, no flow control
+ */
+static void usart_setup(void)
+{
+	rcc_periph_clock_enable(RCC_USART1);
+	rcc_periph_clock_enable(RCC_GPIOA);
+
+	gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, USART_TX);
+	gpio_set_af(GPIOA, GPIO_AF1, USART_TX);
+
+	usart_set_baudrate(USART1, 115200);
+	usart_set_databits(USART1, 8);
+	usart_set_stopbits(USART1, USART_CR2_STOPBITS_1);
+	usart_set_mode(USART1, USART_MODE_TX);
+	usart_set_parity(USART1, USART_PARITY_NONE);
+	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+
+	usart_enable(USART1);
+}
+
+/*
+ * Set up I2C1 on PA9, PA10.
+ * Both pins are internally pulled up, not necessary when external pullup is used.
+ */
+static void i2c_setup(void)
+{
+	rcc_periph_clock_enable(RCC_I2C1);
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_set_i2c_clock_hsi(I2C1);
+
+	i2c_reset(I2C1);
+
+	gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO9 | GPIO10);
+	gpio_set_af(GPIOA, GPIO_AF4, GPIO9 | GPIO10);
+	i2c_peripheral_disable(I2C1);
+	//configure ANFOFF DNF[3:0] in CR1
+	i2c_enable_analog_filter(I2C1);
+	i2c_set_digital_filter(I2C1, 0);
+	/* HSI is at 8Mhz */
+	i2c_set_speed(I2C1, i2c_speed_sm_100k, 8);
+	//configure No-Stretch CR1 (only relevant in slave mode)
+	i2c_enable_stretching(I2C1);
+	//addressing mode
+	i2c_set_7bit_addr_mode(I2C1);
+
+	i2c_peripheral_enable(I2C1);
+}
+
+static void print(const char *s)
+{
+	while (*s)
+		usart_send_blocking(USART1, *s++);
+}
+
+static void printhex(uint8_t h)
+{
+	h &= 0xf;
+	if (h > 9)
+		h += 'A' - '9' - 1;
+
+	usart_send_blocking(USART1, h + '0');
+}
+
+static void print2hex(uint8_t h)
+{
+	printhex(h >> 4);
+	printhex(h & 0xf);
+}
+
+int main(void)
+{
+	clock_setup();
+	usart_setup();
+	i2c_setup();
+	systick_setup(1);  // 1 ms tick
+
+	// write 0x42, 0x75 into address 0x01
+	uint8_t cmdWrite[] = { 0x01, 0x42, 0x75 };
+	i2c_transfer7(I2C1, I2C_MEMORY_ADDR, cmdWrite, sizeof(cmdWrite), NULL, 0);
+
+	delay(5);  // needed for finishing the write (see Datasheet Atmel 24c02)
+
+	// read 2 bytes from address 0x01
+	uint8_t cmdRead[] = { 0x01 };
+	uint8_t dataOut[2];
+	i2c_transfer7(I2C1, I2C_MEMORY_ADDR, cmdRead, sizeof(cmdRead), dataOut, sizeof(dataOut));
+
+	print("Addr 0x01, value = ");
+	print2hex(dataOut[0]);
+	print(" ");
+	print2hex(dataOut[1]);
+	print("\n");
+
+	/* No Main loop */
+	return 0;
+}

examples/stm32/f0/other/stm32f030.ld

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+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2009 Uwe Hermann <[email protected]>
+ * Copyright (C) 2011 Stephen Caudle <[email protected]>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Linker script for STM32F030F4 (16K flash, 4K RAM). */
+
+/* Define memory regions. */
+MEMORY
+{
+	rom (rx) : ORIGIN = 0x08000000, LENGTH = 16K
+	ram (rwx) : ORIGIN = 0x20000000, LENGTH = 4K
+}
+
+/* Include the common ld script. */
+INCLUDE cortex-m-generic.ld
+