New test for SPI loop transfer

examples/NonReg/SPI_loop/SPI_loop/SPI_loop.ino

@@ -0,0 +1,71 @@
+/*
+  SPI_loopback
+
+  Test the loopback transfer on SPI serial link.
+  A test string is sent 9 times and compared to the Rx frame.
+  when the MISO pin is physically connected to the MOSI pin of the SPI bus
+  Default test the SPI_A link.
+  Led remains ON when test ends successfully (off in case of error).
+  To test the transfer on the SPI_B , just define SPI_B pins and connect,
+  as follows:
+    int MOSI_PIN = 22; // to be connected to the B_MISO
+    int SCK_PIN = 23;
+    int CS_PIN = 24;
+    int MISO_PIN = 25; // to be connected to the B_MOSI
+  and configure as follows:
+    SPI.setMISO(MISO_PIN);
+    SPI.setMOSI(MOSI_PIN);
+    SPI.setSCLK(SCK_PIN);
+    SPI.setSSEL(CS_PIN);
+
+  This example code is in the public domain.
+
+*/
+#include "SPI.h"
+
+#define MOSI_PIN  PIN_SPI_MOSI
+#define SCK_PIN   PIN_SPI_SCK
+#define CS_PIN    PIN_SPI_SS
+#define MISO_PIN  PIN_SPI_MOSI
+
+#define BUF_SIZE 36
+uint8_t buffer_tx[] = "Thequickbrownfoxjumpsoverthelazydog\0";
+uint8_t buffer_rx[BUF_SIZE] = {};
+
+/* SPI transfer loop nb */
+#define TEST_LOOP_NB 9
+
+void setup() {
+  uint8_t tested_ok = 0; // test result
+
+  /* the SPI pin configuration is done by the SPI.begin */
+   SPI.begin(CS_PIN); // waking up SPI bus
+  // SPI.setClockDivider(CS_PIN, 256);     // setting a slower clock
+
+  pinMode(LED_BUILTIN, OUTPUT);   // prepare led for status
+  digitalWrite(LED_BUILTIN, LOW); // start with led off
+
+  for (uint8_t received = 0; received < TEST_LOOP_NB; received++) {
+    SPI.transfer(CS_PIN, buffer_tx, buffer_rx, BUF_SIZE, SPI_LAST);
+    delay(100);
+    /* compare what is received to what was sent */
+    if (!memcmp(buffer_tx, buffer_rx, BUF_SIZE)) {
+      /* this transfer passed */
+      tested_ok++;
+    }
+    memset(buffer_rx, 0, BUF_SIZE);
+  }
+  /* display test result */
+  if (tested_ok == TEST_LOOP_NB) {
+      /* success */
+      digitalWrite(LED_BUILTIN, HIGH);
+  } else {
+      /* error */
+      digitalWrite(LED_BUILTIN, LOW);
+  }
+}
+
+void loop() {
+  /* nothing special */
+}
+