ni6501_counter_command
ret = ni6501_counter_command(dev, START_COUNTER, NULL);
ret = ni6501_counter_command(dev, STOP_COUNTER, NULL);
ret = ni6501_counter_command(dev, STOP_COUNTER, NULL);
ret = ni6501_counter_command(dev, WRITE_COUNTER, &val);
ret = ni6501_counter_command(dev, READ_COUNTER, &val);
ret = ni6501_counter_command(dev, WRITE_COUNTER, &val);