def METHOD_NAME(bus, tt, idx):
  dat = [(tt >> 20) & 0xff, (tt >> 12) & 0xff, (tt >> 4) & 0xff,
         ((tt & 0xf) << 4) + (idx << 2)]
  chksum = 0x1000 - dat[0] - dat[1] - dat[2] - dat[3]
  chksum = chksum & 0xfff
  dat += [0x40 + (chksum >> 8), chksum & 0xff, 0x12]
  return make_can_msg(0xa1, bytes(dat), bus)