diff --git a/crc.cc b/crc.cc
new file mode 100644
index 0000000..b13c8a8
--- /dev/null
+++ b/crc.cc
@@ -0,0 +1,114 @@
+
+/* CRC experiments. Some day, the crc checks will actually work. */
+
+#include<stdio.h>
+#include<stdint.h>
+
+typedef unsigned char uchar;
+
+#define CRC16_DNP 0x3D65
+
+uint16_t crc16_dnp_per_byte(uint16_t crc, uchar b)
+{
+    unsigned char i;
+
+    for (i = 0; i < 8; i++) {
+
+        if (((crc & 0x8000) >> 8) ^ (b & 0x80)){
+            crc = (crc << 1)  ^ CRC16_DNP;
+        } else {
+            crc = (crc << 1);
+        }
+
+        b <<= 1;
+    }
+
+    return crc;
+}
+
+uint16_t crc16_dnp(uchar *data, size_t len)
+{
+    uint16_t crc = 0x0000;
+
+    for (size_t i=0; i<len; ++i) {
+        crc = crc16_dnp_per_byte(crc, data[i]);
+    }
+
+    return (~crc);
+}
+
+
+int main() {
+    unsigned char data[4];
+    data[0] = 0x01;
+    data[1] = 0xfd;
+    data[2] = 0x1f;
+    data[3] = 0x01;
+
+    // ./reveng/reveng -m CRC-16/EN-13757 -c 01FD1F01
+    // cc22
+    int crc = crc16_dnp(data, 4);
+    int crc_msb = (crc >> 8)&0xff;
+    int crc_lsb = crc&0xff;
+    printf("%02x %02x\n", crc_msb, crc_lsb);
+
+    if (crc != 0xcc22) {
+        printf("ERROR!\n");
+    }
+    data[3] = 0x00;
+
+    // ./reveng/reveng -m CRC-16/EN-13757 -c 01FD1F00
+    // f147
+    crc = crc16_dnp(data, 4);
+    crc_msb = (crc >> 8)&0xff;
+    crc_lsb = crc&0xff;
+    printf("%02x %02x\n", crc_msb, crc_lsb);
+
+    if (crc != 0xf147) {
+        printf("ERROR!\n");
+    }
+
+    uchar block[10];
+    block[0]=0xEE;
+    block[1]=0x44;
+    block[2]=0x9A;
+    block[3]=0xCE;
+    block[4]=0x01;
+    block[5]=0x00;
+    block[6]=0x00;
+    block[7]=0x80;
+    block[8]=0x23;
+    block[9]=0x07;
+
+    // ./reveng/reveng -m CRC-16/EN-13757 -c EE449ACE010000802307
+    // aabc
+    crc = crc16_dnp(block, 10);
+    crc_msb = (crc >> 8)&0xff;
+    crc_lsb = crc&0xff;
+    printf("%02x %02x\n", crc_msb, crc_lsb);
+
+    if (crc != 0xaabc) {
+        printf("ERROR!\n");
+    }
+
+    // width=16 poly=0x3d65 init=0x0000 refin=false refout=false xorout=0xffff check=0xc2b7 residue=0xa366 name="CRC-16/EN-13757"
+    block[0]='1';
+    block[1]='2';
+    block[2]='3';
+    block[3]='4';
+    block[4]='5';
+    block[5]='6';
+    block[6]='7';
+    block[7]='8';
+    block[8]='9';
+
+    crc = crc16_dnp(block, 9);
+    crc_msb = (crc >> 8)&0xff;
+    crc_lsb = crc&0xff;
+    printf("%02x %02x\n", crc_msb, crc_lsb);
+
+    if (crc != 0xc2b7) {
+        printf("ERROR!\n");
+    }
+
+}
diff --git a/meter_multical21.cc b/meter_multical21.cc
index 595f188..fecf1da 100644
--- a/meter_multical21.cc
+++ b/meter_multical21.cc
@@ -203,14 +203,13 @@ void MeterMultical21::processContent(Telegram *t)
         // has to wait a bit.
         t->addExplanation(bytes, 4, "%02x%02x%02x%02x ecrc", ecrc0, ecrc1, ecrc2, ecrc3);
 
-        vector<uchar>::iterator data = t->content.begin()+7;
-        size_t data_len = t->content.size()-7;
-        map<string,pair<int,string>> values;
-        uint16_t format_hash;
+        // So we hardcode the format string here.
         vector<uchar> format_bytes;
         hex2bin("02FF2004134413", &format_bytes);
         vector<uchar>::iterator format = format_bytes.begin();
-        parseDV(t, data, data_len, &values, &format, format_bytes.size(), &format_hash);
+
+        map<string,pair<int,string>> values;
+        parseDV(t, t->content.begin()+7, t->content.size()-7, &values, &format, format_bytes.size());
 
         int offset;
 
@@ -234,11 +233,8 @@ void MeterMultical21::processContent(Telegram *t)
             warning("\n");
         }
 
-        vector<uchar>::iterator data = t->content.begin()+3;
-        size_t data_len = t->content.size()-3-4; // Why this number?
         map<string,pair<int,string>> values;
-        uint16_t format_hash;
-        parseDV(t, data, data_len, &values, NULL, 0, &format_hash);
+        parseDV(t, t->content.begin()+3, t->content.size()-3-4, &values);
 
         // There are two more bytes in the data. Unknown purpose.
         int val0 = t->content[20];
@@ -258,7 +254,8 @@ void MeterMultical21::processContent(Telegram *t)
         t->addMoreExplanation(offset, " target consumption (%f m3)", target_volume_);
 
         // To unknown bytes, seems to be very constant.
-        t->addExplanation(data, 2, "%02x%02x unknown", val0, val1);
+        vector<uchar>::iterator unknowns = t->content.begin()+20;
+        t->addExplanation(unknowns, 2, "%02x%02x unknown", val0, val1);
     } else {
         warning("(multical21) warning: unknown frame %02x (did you use the correct encryption key?)\n", frame_type);
     }