struct packet {
    unsigned int duration;
    unsigned int count;
    u8 data[DATA_MAX]; // payload
};

int rfm12_ask_modulate(struct packet *packet)
{
    unsigned int duration = packet->duration;
    unsigned int count = packet->count;
    u8 *data = packet->data;
    DBG_FMT("got packet:\n  duration: %i\n  count: %i\n  data: %s\n", duration, count, data);
    int i;
    for(;count>0;count--) {
        for(i=0;data[i]!='\0';i++) {
            unsigned int us = duration;
            switch(data[i]) {
                case '1':
                    DBG("switch on TX\n");
                    rfm12_tx_on();
                    for(;us>0;us--)
                        udelay(1);
                    break;
                case '0':
                    DBG("switch off TX\n");
                    rfm12_tx_off();
                    for(;us>0;us--)
                        udelay(1);
                    break;
               default:
                    DBG_FMT("MOEP! character <%c> is invalid!\n", data[i]);
                    return -EINVAL;
            }
        }
    }
    return 0;
}