hyundai: TCS13 checksum (#623)

board/safety/safety_hyundai.h

@@ -94,6 +94,9 @@ static uint8_t hyundai_compute_checksum(CAN_FIFOMailBox_TypeDef *to_push) {
   } else {
     // sum of nibbles
     for (int i = 0; i < 8; i++) {
+      if ((addr == 916) && (i == 7)) {
+        continue; // exclude
+      }
       uint8_t b = GET_BYTE(to_push, i);
       if (((addr == 608) && (i == 7)) || ((addr == 916) && (i == 6)) || ((addr == 1057) && (i == 7))) {
         b &= (addr == 1057) ? 0x0FU : 0xF0U; // remove checksum

tests/safety/test_hyundai.py

@@ -41,6 +41,8 @@ def checksum(msg):
         b &= 0x0F if addr == 1057 else 0xF0
       elif addr == 916 and i == 6:
         b &= 0xF0
+      elif addr == 916 and i == 7:
+        continue
       chksum += sum(divmod(b, 16))
     chksum = (16 - chksum) % 16
     ret = bytearray(dat)