From 45b51dea1208fec87077ce48808481b1d7a02406 Mon Sep 17 00:00:00 2001
From: Victor Lamoine <victor.lamoine@gmail.com>
Date: Fri, 20 Apr 2018 14:38:57 +0200
Subject: [PATCH] Add simple SPI slave example

---
 .../SPI/examples/spi_slave/spi_slave.ino      | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 STM32F1/libraries/SPI/examples/spi_slave/spi_slave.ino

diff --git a/STM32F1/libraries/SPI/examples/spi_slave/spi_slave.ino b/STM32F1/libraries/SPI/examples/spi_slave/spi_slave.ino
new file mode 100644
index 0000000..f0122d6
--- /dev/null
+++ b/STM32F1/libraries/SPI/examples/spi_slave/spi_slave.ino
@@ -0,0 +1,46 @@
+// SPI slave example
+// STM32 acts as a SPI slave an reads 8 bit data frames over SPI
+// The data sent to the master is a simple count (0, 1, 2, 3) that is incremented
+// each time a data frame is received.
+// Serial output is here for debug
+
+#include <SPI.h>
+#include <cstdint>
+
+void setupSPI(void)
+{
+  pinMode(PA7, INPUT); // MOSI1
+  pinMode(PA6, INPUT); // MISO1
+  pinMode(PA5, INPUT); // SCK
+  pinMode(BOARD_SPI_DEFAULT_SS, INPUT); // SS
+
+  // Select SPI1
+  SPI.setModule(1);
+  // The clock value is not used
+  SPI.beginTransactionSlave(SPISettings(18000000, MSBFIRST, SPI_MODE0, DATA_SIZE_8BIT));
+}
+
+void setup()
+{
+  Serial.begin(115200);
+  delay(100);
+
+  // Data that master will receive when transferring a data frame over SPI
+  SPI.dev()->regs->DR = 0;
+  setupSPI();
+}
+
+uint8_t count(0);
+void loop()
+{
+  // Blocking call to read SPI message
+  uint8_t msg(SPI.read());
+  Serial.print("Received = 0b");
+  Serial.print(msg, BIN);
+  Serial.print(", 0x");
+  Serial.print(msg, HEX);
+  Serial.print(", ");
+  Serial.println(msg);
+  // Next data frame that will be received by master
+  SPI.dev()->regs->DR = ++count;
+}