Add decode_uart util (#1376)

include/util.h

@@ -52,8 +52,18 @@ void reflect_nibbles(uint8_t message[], unsigned num_bytes);
 /// @param offset_bits start offset of message in bits
 /// @param num_bits message length in bits
 /// @param dst target buffer for extracted nibbles, at least num_bits/5 size
+/// @return number of successfully unstuffed nibbles.
 unsigned extract_nibbles_4b1s(uint8_t *message, unsigned offset_bits, unsigned num_bits, uint8_t *dst);
 
+/// UART "8n1" (10-to-8) decoder with 1 start bit (0), no parity, 1 stop bit (1), LSB-first bit-order.
+///
+/// @param message bytes of message data
+/// @param offset_bits start offset of message in bits
+/// @param num_bits message length in bits
+/// @param dst target buffer for extracted bytes, at least num_bits/10 size
+/// @return number of successful decoded bytes
+unsigned extract_bytes_uart(uint8_t *message, unsigned offset_bits, unsigned num_bits, uint8_t *dst);
+
 /// CRC-4.
 ///
 /// @param message array of bytes to check

src/devices/flex.c

@@ -91,6 +91,7 @@ struct flex_params {
     unsigned preamble_len;
     bitrow_t preamble_bits;
     struct flex_get getter[GETTER_SLOTS];
+    unsigned decode_uart;
 };
 
 static void print_row_bytes(char *row_bytes, uint8_t *bits, int num_bits)
@@ -213,6 +214,14 @@ static int flex_callback(r_device *decoder, bitbuffer_t *bitbuffer)
             return DECODE_FAIL_SANITY;
     }
 
+    if (params->decode_uart) {
+        for (i = 0; i < bitbuffer->num_rows; i++) {
+            int len = extract_bytes_uart(bitbuffer->bb[i], 0, bitbuffer->bits_per_row[i], tmp);
+            memcpy(bitbuffer->bb[i], tmp, len);
+            bitbuffer->bits_per_row[i] = len * 8;
+        }
+    }
+
     if (decoder->verbose) {
         fprintf(stderr, "%s: ", params->name);
         bitbuffer_print(bitbuffer);
@@ -658,6 +667,9 @@ r_device *flex_create_device(char *spec)
         else if (!strcasecmp(key, "unique"))
             params->unique = val ? atoi(val) : 1;
 
+        else if (!strcasecmp(key, "decode_uart"))
+            params->decode_uart = val ? atoi(val) : 1;
+
         else if (!strcasecmp(key, "get")) {
             if (get_count < GETTER_SLOTS)
                 parse_getter(val, &params->getter[get_count++]);

src/util.c

@@ -61,6 +61,33 @@ unsigned extract_nibbles_4b1s(uint8_t *message, unsigned offset_bits, unsigned n
     return ret;
 }
 
+unsigned extract_bytes_uart(uint8_t *message, unsigned offset_bits, unsigned num_bits, uint8_t *dst)
+{
+    unsigned ret = 0;
+
+    while (num_bits >= 10) {
+        int startb = message[offset_bits / 8] >> (7 - (offset_bits % 8));
+        offset_bits += 1;
+        int datab = message[offset_bits / 8];
+        if (offset_bits % 8) {
+            datab = (message[offset_bits / 8] << 8) | message[offset_bits / 8 + 1];
+            datab >>= 8 - (offset_bits % 8);
+        }
+        offset_bits += 8;
+        int stopb = message[offset_bits / 8] >> (7 - (offset_bits % 8));
+        offset_bits += 1;
+        if ((startb & 1) != 0)
+            break; // start-bit error
+        if ((stopb & 1) != 1)
+            break; // stop-bit error
+        *dst++ = reverse8(datab & 0xff);
+        ret += 1;
+        num_bits -= 10;
+    }
+
+    return ret;
+}
+
 uint8_t crc4(uint8_t const message[], unsigned nBytes, uint8_t polynomial, uint8_t init)
 {
     unsigned remainder = init << 4; // LSBs are unused
@@ -316,14 +343,51 @@ int add_nibbles(uint8_t const message[], unsigned num_bytes)
 
 // Unit testing
 #ifdef _TEST
+#define ASSERT_EQUALS(a, b) \
+    do { \
+        if ((a) == (b)) \
+            ++passed; \
+        else { \
+            ++failed; \
+            fprintf(stderr, "FAIL: %d <> %d\n", (a), (b)); \
+        } \
+    } while (0)
+
 int main(int argc, char **argv) {
+    unsigned passed = 0;
+    unsigned failed = 0;
+
     fprintf(stderr, "util:: test\n");
 
     uint8_t msg[] = {0x08, 0x0a, 0xe8, 0x80};
 
-    fprintf(stderr, "util::crc8(): odd parity:  %02X\n", crc8(msg, 3, 0x80, 0x00));
-    fprintf(stderr, "util::crc8(): even parity: %02X\n", crc8(msg, 4, 0x80, 0x00));
+    fprintf(stderr, "util::crc8(): odd parity\n");
+    ASSERT_EQUALS(crc8(msg, 3, 0x80, 0x00), 0x80);
 
-    return 0;
+    fprintf(stderr, "util::crc8(): even parity\n");
+    ASSERT_EQUALS(crc8(msg, 4, 0x80, 0x00), 0x00);
+
+    // sync-word 0b0 0xff 0b1 0b0 0x33 0b1 (i.e. 0x7fd99, note that 0x33 is 0xcc "on the wire")
+    uint8_t uart[]   = {0x7f, 0xd9, 0x90};
+    uint8_t bytes[6] = {0};
+
+    // y0 xff y1 y0 xcc y1 y0 x80 y1 y0 x40 y1 y0 xc0 y1
+    uint8_t uart123[] = {0x07, 0xfd, 0x99, 0x40, 0x48, 0x16, 0x04, 0x00};
+
+    fprintf(stderr, "util::extract_bytes_uart():\n");
+    ASSERT_EQUALS(extract_bytes_uart(uart, 0, 24, bytes), 2);
+    ASSERT_EQUALS(bytes[0], 0xff);
+    ASSERT_EQUALS(bytes[1], 0x33);
+
+    ASSERT_EQUALS(extract_bytes_uart(uart123, 4, 60, bytes), 5);
+    ASSERT_EQUALS(bytes[0], 0xff);
+    ASSERT_EQUALS(bytes[1], 0x33);
+    ASSERT_EQUALS(bytes[2], 0x01);
+    ASSERT_EQUALS(bytes[3], 0x02);
+    ASSERT_EQUALS(bytes[4], 0x03);
+
+    fprintf(stderr, "util:: test (%u/%u) passed, (%u) failed.\n", passed, passed + failed, failed);
+
+    return failed;
 }
 #endif /* _TEST */