added minimal ibis driver example

ibus/ibus.c

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2022 Oleg Borodin  <borodin@unix7.org>
+ */
+
+
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include <ibus.h>
+
+#define IBUS_FRAMESIZE 32
+#define IBUS_CHANNELS  14
+
+void ibus_init(ibus_t* bus) {
+    memset(bus->iframe, 0, sizeof(bus->iframe));
+    memset(bus->rcvalue, 0, sizeof(bus->rcvalue));
+    bus->findex = 0;
+}
+
+
+bool ibus_recv(ibus_t* bus, uint8_t ibyte) {
+
+    if(bus->findex == 0 && ibyte != 0x20) {
+        return false;
+    }
+    if(bus->findex == 1 && ibyte != 0x40) {
+        bus->findex = 0;
+        return false;
+    }
+    if(bus->findex < IBUS_FRAMESIZE) {
+        bus->iframe[bus->findex++] = ibyte;
+        return false;
+    }
+
+    if(bus->findex == IBUS_FRAMESIZE) {
+        bus->findex = 0;
+        uint16_t chksum = 0xFFFF;
+        for (int i = 0; i < 30; i++) {
+            chksum -= bus->iframe[i];
+        }
+        uint16_t rxsum = bus->iframe[30] + (bus->iframe[31] << 8);
+        if (chksum == rxsum) {
+            for (int c = 0; c < IBUS_CHANNELS; c++) {
+                int offset = c * 2 + 2;
+                uint16_t hival = ((bus->iframe[offset + 1] & 0x0F) << 8);
+                uint16_t loval = bus->iframe[offset] & 0xFF;
+                bus->rcvalue[c] = hival + loval;
+            }
+            return true;
+        }
+    }
+    return false;
+}
+
+int ibus_chcount(ibus_t* bus) {
+    return IBUS_CHANNELS;
+}
+
+int16_t ibus_getch(ibus_t* bus, int num) {
+    if (num < IBUS_CHANNELS) {
+        return (int16_t)bus->rcvalue[num];
+    }
+    return WRONG_RCVAL;
+}