diff --git a/lib/busvoodoo_spi.c b/lib/busvoodoo_spi.c
new file mode 100644
index 0000000..0f252e5
--- /dev/null
+++ b/lib/busvoodoo_spi.c
@@ -0,0 +1,310 @@
+/* This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+/** BusVoodoo SPI mode (code)
+ *  @file busvoodoo_spi.c
+ *  @author King Kévin <kingkevin@cuvoodoo.info>
+ *  @date 2018
+ *  @note peripherals used: SPI @ref busvoodoo_spi
+ */
+/* standard libraries */
+#include <stdint.h> // standard integer types
+#include <stdlib.h> // standard utilities
+#include <string.h> // string utilities
+
+/* STM32 (including CM3) libraries */
+#include <libopencm3/stm32/gpio.h> // general purpose input output library
+#include <libopencm3/stm32/rcc.h> // real-time control clock library
+#include <libopencm3/stm32/spi.h> // SPI library
+
+/* own libraries */
+#include "global.h" // board definitions
+#include "print.h" // printing utilities
+#include "menu.h" // menu definitions
+#include "busvoodoo_global.h" // BusVoodoo definitions
+#include "busvoodoo_oled.h" // OLED utilities
+#include "busvoodoo_spi.h" // own definitions
+
+/** @defgroup busvoodoo_spi SPI peripheral used for SPI communication
+ *  @{
+ */
+#define BUSVOODOO_SPI_ID 2 /**< SPI peripheral */
+/** @} */
+
+/** mode setup stage */
+static enum busvoodoo_spi_setting_t {
+	BUSVOODOO_SPI_SETTING_NONE,
+	BUSVOODOO_SPI_SETTING_DUPLEX,
+	BUSVOODOO_SPI_SETTING_FREQUENCY,
+	BUSVOODOO_SPI_SETTING_DATABITS,
+	BUSVOODOO_SPI_SETTING_BITORDER,
+	BUSVOODOO_SPI_SETTING_MODE,
+	BUSVOODOO_SPI_SETTING_DRIVE,
+	BUSVOODOO_SPI_SETTING_DONE,
+} busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_NONE;
+/** SPI duplex mode (true = full-duplex, false = bidirectional) */
+static bool busvoodoo_spi_duplex = true;
+/** SPI baud rate (corresponding to baud rate control, e.g. 36MHz/(2<<br))) */
+static uint8_t busvoodoo_spi_baudrate = 1;
+/** SPI data frame bit width (8 or 16) */
+static uint8_t busvoodoo_spi_databits = 8;
+/** SPI data frame bit order (true = MSB, false = LSB) */
+static bool busvoodoo_spi_bitorder = true;
+/** SPI mode (defining clock polarity and phase) */
+static uint8_t busvoodoo_spi_standard_mode = 0;
+/** pin drive mode (true = push-pull, false = open-drain) */
+static bool busvoodoo_spi_drive = true;
+/** if embedded pull-up resistors are used */
+static bool busvoodoo_spi_pullup = true;
+
+/** setup SPI mode
+ *  @param[out] prefix terminal prompt prefix
+ *  @param[in] line terminal prompt line to configure mode
+ *  @return if setup is complete
+ */
+static bool busvoodoo_spi_setup(char** prefix, const char* line)
+{
+	bool complete = false; // is the setup complete
+	if (NULL==line) { // first call
+		busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_NONE; // re-start configuration
+	}
+	switch (busvoodoo_spi_setting) {
+		case BUSVOODOO_SPI_SETTING_NONE:
+			busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DUPLEX;
+			printf("1) full-duplex\n");
+			printf("2) bidirectional\n");
+			snprintf(busvoodoo_global_string, LENGTH(busvoodoo_global_string), "duplex mode (1,2) [%c]", busvoodoo_spi_duplex ? '1' : '2');
+			*prefix = busvoodoo_global_string; // ask for setting
+			break;
+		case BUSVOODOO_SPI_SETTING_DUPLEX:
+			if (NULL==line || 0==strlen(line)) { // use default setting
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_FREQUENCY; // go to next setting
+			} else if (1==strlen(line)) { // setting provided
+				uint8_t duplex = atoi(line); // parse setting
+				if (1==duplex || 2==duplex) { // check setting
+					busvoodoo_spi_duplex = (1==duplex); // remember setting
+					busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_FREQUENCY; // go to next setting
+				}
+			}
+			if (BUSVOODOO_SPI_SETTING_FREQUENCY==busvoodoo_spi_setting) { // if next setting
+				// SPI2 used APB1 as PCLK, which has a maximum frequency of 36 MHz
+				for (uint8_t div=0; div<8; div++) {
+					printf("%u) %u kHz\n", div+1, 36000/(2<<div)); // print possible frequencies
+				}
+				snprintf(busvoodoo_global_string, LENGTH(busvoodoo_global_string), "frequency (1-9) [%u]", busvoodoo_spi_baudrate+1);
+				*prefix = busvoodoo_global_string; // display next setting
+			}
+			break;
+		case BUSVOODOO_SPI_SETTING_FREQUENCY:
+			if (NULL==line || 0==strlen(line)) { // use default setting
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DATABITS; // go to next setting
+			} else if (1==strlen(line)) { // setting provided
+				uint8_t baudrate = atoi(line); // parse setting
+				if (baudrate>0 && baudrate<=9) { // check setting
+					busvoodoo_spi_baudrate = baudrate-1; // remember setting
+					busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DATABITS; // go to next setting
+				}
+			}
+			if (BUSVOODOO_SPI_SETTING_DATABITS==busvoodoo_spi_setting) { // if next setting
+				snprintf(busvoodoo_global_string, LENGTH(busvoodoo_global_string), "data frame width in bits (8,16) [%u]", busvoodoo_spi_databits); // prepare next setting
+				*prefix = busvoodoo_global_string; // display next setting
+			}
+			break;
+		case BUSVOODOO_SPI_SETTING_DATABITS:
+			if (NULL==line || 0==strlen(line)) { // use default setting
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_BITORDER; // go to next setting
+			} else if (1==strlen(line) || 2==strlen(line)) { // setting provided
+				uint8_t databits = atoi(line); // parse setting
+				if (8==databits || 16==databits) { // check setting
+					busvoodoo_spi_databits = databits; // remember setting
+					busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_BITORDER; // go to next setting
+				}
+			}
+			if (BUSVOODOO_SPI_SETTING_BITORDER==busvoodoo_spi_setting) { // if next setting
+				printf("1) most significant bit first\n");
+				printf("2) least significant bit first\n");
+				snprintf(busvoodoo_global_string, LENGTH(busvoodoo_global_string), "data frame bit order (1,2) [%c]", busvoodoo_spi_bitorder ? '1' : '2'); // prepare next setting
+				*prefix = busvoodoo_global_string; // display next setting
+			}
+			break;
+		case BUSVOODOO_SPI_SETTING_BITORDER:
+			if (NULL==line || 0==strlen(line)) { // use default setting
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_MODE; // go to next setting
+			} else if (1==strlen(line)) { // setting provided
+				uint8_t bitorder = atoi(line); // parse setting
+				if (1==bitorder || 2==bitorder) { // check setting
+					busvoodoo_spi_bitorder = (1==bitorder); // remember setting
+					busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_MODE; // go to next setting
+				}
+			}
+			if (BUSVOODOO_SPI_SETTING_MODE==busvoodoo_spi_setting) { // if next setting
+				printf("1) mode 0 (clock polarity: idle low, clock phase: sample data on rising edge)\n");
+				printf("2) mode 1 (clock polarity: idle low, clock phase: sample data on falling edge)\n");
+				printf("3) mode 2 (clock polarity: idle high, clock phase: sample data on falling edge)\n");
+				printf("4) mode 3 (clock polarity: idle high, clock phase: sample data on rising edge)\n");
+				snprintf(busvoodoo_global_string, LENGTH(busvoodoo_global_string), "mode (1,2,3,4) [%u]", busvoodoo_spi_standard_mode+1); // prepare next setting
+				*prefix = busvoodoo_global_string; // display next setting
+			}
+			break;
+		case BUSVOODOO_SPI_SETTING_MODE:
+			if (NULL==line || 0==strlen(line)) { // use default setting
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DRIVE; // go to next setting
+			} else if (1==strlen(line)) { // setting provided
+				uint8_t mode = atoi(line); // parse setting
+				if (mode>=1 && mode<=4) {
+					busvoodoo_spi_standard_mode = mode-1; // remember setting
+					busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DRIVE; // go to next setting
+				}
+			}
+			if (BUSVOODOO_SPI_SETTING_DRIVE==busvoodoo_spi_setting) { // if next setting
+				printf("1) push-pull (3.3V)\n");
+				printf("2) open-drain, with embedded pull-up (2kO)\n");
+				printf("2) open-drain, with external pull-up\n");
+				snprintf(busvoodoo_global_string, LENGTH(busvoodoo_global_string), "drive mode (1,2,3) [%c]", busvoodoo_spi_drive ? '1' : (busvoodoo_spi_pullup ? '2' : '3')); // show drive mode
+				*prefix = busvoodoo_global_string; // display next setting
+			}
+			break;
+		case BUSVOODOO_SPI_SETTING_DRIVE:
+			if (NULL==line || 0==strlen(line)) { // use default setting
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DONE; // go to next setting
+			} else if (1==strlen(line)) { // setting provided
+				uint8_t drive = atoi(line); // parse setting
+				if (1==drive || 2==drive || 3==drive) { // check setting
+					busvoodoo_spi_drive = (1==drive); // remember setting
+					busvoodoo_spi_pullup = (2==drive); // remember setting
+					if (!busvoodoo_spi_drive && busvoodoo_spi_pullup) {
+						printf("use LV to set voltage\n");
+					}
+					busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_DONE; // go to next setting
+				}
+			}
+			if (BUSVOODOO_SPI_SETTING_DONE==busvoodoo_spi_setting) { // we have all settings, configure UART
+				rcc_periph_clock_enable(RCC_AFIO); // enable clock for SPI alternate function
+				rcc_periph_clock_enable(RCC_SPI(BUSVOODOO_SPI_ID)); // enable clock for SPI peripheral
+				spi_reset(SPI(BUSVOODOO_SPI_ID)); // clear SPI values to default
+				spi_set_baudrate_prescaler(SPI(BUSVOODOO_SPI_ID), busvoodoo_spi_baudrate); // set baud rate (i.e. frequency)
+				spi_set_standard_mode(SPI(BUSVOODOO_SPI_ID), busvoodoo_spi_standard_mode); // set SPI mode
+				if (8==busvoodoo_spi_databits) { // set data frame bit width
+					spi_set_dff_8bit(SPI(BUSVOODOO_SPI_ID)); // set to 8 bits
+				} else {
+					spi_set_dff_16bit(SPI(BUSVOODOO_SPI_ID)); // set to 16 bits
+				}
+				if (busvoodoo_spi_bitorder) { // set bit order
+					spi_send_msb_first(SPI(BUSVOODOO_SPI_ID)); // MSb-first
+				} else {
+					spi_send_lsb_first(SPI(BUSVOODOO_SPI_ID)); // LSb-first
+				}
+				rcc_periph_clock_enable(RCC_SPI_MOSI_PORT(BUSVOODOO_SPI_ID)); // enable clock for GPIO peripheral for MOSI signal
+				if (busvoodoo_spi_drive) {
+					gpio_set_mode(SPI_MOSI_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, SPI_MOSI_PIN(BUSVOODOO_SPI_ID)); // set MOSI as output
+				} else {
+					gpio_set_mode(SPI_MOSI_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, SPI_MOSI_PIN(BUSVOODOO_SPI_ID)); // set MOSI as output
+				}
+				if (busvoodoo_spi_duplex) {
+					spi_set_full_duplex_mode(SPI(BUSVOODOO_SPI_ID)); // set full duplex mode
+					rcc_periph_clock_enable(RCC_SPI_MISO_PORT(BUSVOODOO_SPI_ID)); // enable clock for GPIO peripheral for MISO signal
+					if (busvoodoo_spi_drive) {
+						gpio_set_mode(SPI_MISO_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_MISO_PIN(BUSVOODOO_SPI_ID)); // set MISO as output
+					} else {
+						gpio_set_mode(SPI_MISO_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_MISO_PIN(BUSVOODOO_SPI_ID)); // set MISO as output
+					}
+				} else {
+					spi_set_bidirectional_mode(SPI(BUSVOODOO_SPI_ID)); // set bidirectional mode
+				}
+				rcc_periph_clock_enable(RCC_SPI_SCK_PORT(BUSVOODOO_SPI_ID)); // enable clock for GPIO peripheral for SCK signal
+				if (busvoodoo_spi_drive) {
+					gpio_set_mode(SPI_SCK_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, SPI_SCK_PIN(BUSVOODOO_SPI_ID)); // set NSS as output
+				} else {
+					gpio_set_mode(SPI_NSS_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, SPI_NSS_PIN(BUSVOODOO_SPI_ID)); // set NSS as output
+				}
+				spi_enable_software_slave_management(SPI(BUSVOODOO_SPI_ID)); // control SS by software
+				rcc_periph_clock_enable(RCC_SPI_NSS_PORT(BUSVOODOO_SPI_ID)); // enable clock for GPIO peripheral for SS signal
+				gpio_set(SPI_NSS_PORT(BUSVOODOO_SPI_ID), SPI_NSS_PIN(BUSVOODOO_SPI_ID)); // de-select slave (on high)
+				if (busvoodoo_spi_drive) {
+					gpio_set_mode(SPI_NSS_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, SPI_NSS_PIN(BUSVOODOO_SPI_ID)); // set NSS as output
+				} else {
+					gpio_set_mode(SPI_NSS_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, SPI_NSS_PIN(BUSVOODOO_SPI_ID)); // set NSS as output
+				}
+				spi_set_master_mode(SPI(BUSVOODOO_SPI_ID)); // set master mode
+				spi_enable(SPI(BUSVOODOO_SPI_ID)); // enable SPI
+				if (!busvoodoo_spi_drive) { // in open drain mode
+					busvoodoo_embedded_pullup(busvoodoo_spi_pullup); // set embedded pull-ups
+				}
+				led_off(); // disable LED because there is no activity
+				busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_NONE; // restart settings next time
+				*prefix = "SPI"; // display mode
+				busvoodoo_oled_text_left(*prefix); // set mode title on OLED display
+				const char* pinout_io[10] =  {"GND", "3V3", "5V", "LV", NULL, NULL, "MISO", "SCK", "MOSI", "SS"}; // SPI mode pinout
+				if (!busvoodoo_spi_duplex) {
+					pinout_io[6] = NULL; // MISO is not used
+					pinout_io[8] = "MOSIMISO"; // MOSI is also used as MISO
+				}
+				for (uint8_t i=0; i<LENGTH(pinout_io) && i<LENGTH(busvoodoo_global_pinout_io); i++) {
+					busvoodoo_global_pinout_io[i] = pinout_io[i]; // set pin names
+				}
+				busvoodoo_oled_text_pinout(pinout_io, true); // set pinout on display
+				busvoodoo_oled_update(); // update display to show text and pinout
+				complete = true; // configuration is complete
+			}
+			break;
+		default: // unknown case
+			busvoodoo_spi_setting = BUSVOODOO_SPI_SETTING_NONE; // restart settings next time
+			break;
+	}
+	return complete;
+}
+
+/** exit UART mode
+ */
+static void busvoodoo_spi_exit(void)
+{
+	spi_reset(SPI(BUSVOODOO_SPI_ID)); // clear SPI values to default
+	spi_disable(SPI(BUSVOODOO_SPI_ID)); // disable SPI
+	rcc_periph_clock_disable(RCC_SPI(BUSVOODOO_SPI_ID)); // disable domain clock
+	gpio_set_mode(SPI_SCK_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_SCK_PIN(BUSVOODOO_SPI_ID)); // set pin back to floating input
+	gpio_set_mode(SPI_NSS_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_NSS_PIN(BUSVOODOO_SPI_ID)); // set pin back to floating input
+	gpio_set_mode(SPI_MISO_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_MISO_PIN(BUSVOODOO_SPI_ID)); // set pin back to floating input
+	gpio_set_mode(SPI_MOSI_PORT(BUSVOODOO_SPI_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, SPI_MOSI_PIN(BUSVOODOO_SPI_ID)); // set pin back to floating input
+	busvoodoo_embedded_pullup(false); // disable embedded pull-ups
+}
+
+// command handlers
+
+/** command to transmit and receive data
+ *  @param[in] argument no argument required
+ */
+static void busvoodoo_spi_command_transceive(void* argument)
+{
+	(void)argument; // we won't use the argument
+}
+
+static const struct menu_command_t busvoodoo_spi_commands[] = {
+	{
+		'x',
+		"transceive",
+		"transmit and receive data",
+		MENU_ARGUMENT_NONE,
+		NULL,
+		&busvoodoo_spi_command_transceive,
+	},
+};
+
+struct busvoodoo_mode_t busvoodoo_spi_mode = {
+	"spi",
+	"Serial Peripheral Interface",
+	&busvoodoo_spi_setup,
+	busvoodoo_spi_commands,
+	LENGTH(busvoodoo_spi_commands),
+	&busvoodoo_spi_exit,
+};
diff --git a/lib/busvoodoo_spi.h b/lib/busvoodoo_spi.h
new file mode 100644
index 0000000..510847d
--- /dev/null
+++ b/lib/busvoodoo_spi.h
@@ -0,0 +1,23 @@
+/* This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+/** BusVoodoo SPI mode (API)
+ *  @file busvoodoo_spi.h
+ *  @author King Kévin <kingkevin@cuvoodoo.info>
+ *  @date 2018
+ *  @note peripherals used: SPI @ref busvoodoo_spi
+ */
+
+/** SPI mode interface definition */
+extern struct busvoodoo_mode_t busvoodoo_spi_mode;