AP_RCProtocol: added a test suite for SBUS encode/decode

cover all values and check special handling of 875

libraries/AP_RCProtocol/tests/test_sbus.cpp

@@ -0,0 +1,46 @@
+/*
+  test that SBUS decoding matches SBUS encoding
+ */
+#include <AP_gtest.h>
+#include <AP_SBusOut/AP_SBusOut.h>
+#include <AP_RCProtocol/AP_RCProtocol.h>
+#include <AP_RCProtocol/AP_RCProtocol_SBUS.h>
+
+#define SBUS_RANGE_MIN 200
+#define SBUS_RANGE_MAX 1800
+#define SBUS_RANGE_RANGE (SBUS_RANGE_MAX - SBUS_RANGE_MIN)
+
+#define SBUS_TARGET_MIN 1000
+#define SBUS_TARGET_MAX 2000
+#define SBUS_TARGET_RANGE (SBUS_TARGET_MAX - SBUS_TARGET_MIN)
+
+// this is 875
+#define SBUS_SCALE_OFFSET (SBUS_TARGET_MIN - ((SBUS_TARGET_RANGE * SBUS_RANGE_MIN / SBUS_RANGE_RANGE)))
+
+TEST(SBUSEncodeDecode, test_sbus_encode_decode)
+{
+    const uint8_t num_channels = 8;
+    uint16_t values_in[num_channels];
+    uint16_t values_out[num_channels];
+    uint8_t frame[25];
+
+    for (uint16_t v=875;v<2155; v++) {
+        for (uint8_t i=0; i<num_channels; i++) {
+            values_in[i] = v;
+        }
+        AP_SBusOut::sbus_format_frame(values_in, num_channels, frame);
+        uint16_t num_values = 0;
+        bool sbus_failsafe=false;
+        AP_RCProtocol_SBUS::sbus_decode(frame, values_out, &num_values, sbus_failsafe, num_channels);
+        EXPECT_EQ(sbus_failsafe, values_in[0] == 875);
+        for (uint8_t i=0; i<num_channels; i++) {
+            if (values_in[i] != values_out[i]) {
+                EXPECT_EQ(values_in[i], values_out[i]);
+            }
+        }
+    }
+}
+
+
+AP_GTEST_MAIN()
+int hal = 0;

libraries/AP_RCProtocol/tests/wscript

@@ -0,0 +1,8 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+def build(bld):
+    bld.ap_find_tests(
+        use='ap',
+        DOUBLE_PRECISION_SOURCES = ['test_math_double.cpp', 'test_vector3.cpp']
+    )