// print 32bit unsigned int as hex
void printuhex(uint32_t val){
    addtobuf("0x");
    uint8_t *ptr = (uint8_t*)&val + 3;
    int8_t i, j;
    for(i = 0; i < 4; ++i, --ptr){
        if(*ptr == 0 && i != 3) continue; // omit leading zeros
        for(j = 1; j > -1; --j){
            uint8_t half = (*ptr >> (4*j)) & 0x0f;
            if(half < 10) bufputchar(half + '0');
            else bufputchar(half - 10 + 'a');
        }
    }
}