Sample code for reading POSTAGE scale with Arduino and USB Host Shield

PL2303_USB_Arduino_Demo.cpp

#include <Arduino.h>
#include <usbhub.h>
#include <cdcprolific.h>
#include <SPI.h>

void print(String a, uint8_t b)
{
    Serial.print(a);
    Serial.print(' ');
    Serial.println(b);
}

class PL2303_Oper : public CDCAsyncOper
{
public:
    uint8_t OnInit(ACM *pacm);
};

uint8_t PL2303_Oper::OnInit(ACM *pacm)
{
    LINE_CODING	lc;
    lc.dwDTERate	= 2400;
    lc.bDataBits	= 8;    // 8
    lc.bParityType	= 0;    // N parity
    lc.bCharFormat	= 0;    // 1 stop
    uint8_t rcode = pacm->SetControlLineState(3);
    if (rcode) print("SetControlLineState returned", rcode);
    if (!rcode) rcode = pacm->SetLineCoding(&lc);
    if (rcode) print("SetLineCoding returned", rcode);
    return rcode;
}

USB     Usb;
PL2303_Oper  AsyncOper;
PL2303  Acm(&Usb, &AsyncOper);

void setup()
{
  Serial.begin( 9600 );
  delay(100);
  Serial.println("Start");
  if (Usb.Init() == -1)
      Serial.println("Usb.Init failed: OSCOKIRQ failed to assert");
  delay( 200 );
}

String data;
int ready = 0;
int i =0;
void loop()
{
    Usb.Task();

    Serial.print(i++); Serial.print("\r");

    if (Acm.isReady()) 
    {
        Serial.println();
        delay(50);
        uint8_t  buf[64];
        uint16_t rcvd = 64;

        uint8_t rcode = Acm.RcvData(&rcvd, buf);

        Serial.println("rcvdata");


        if (rcode && rcode != hrNAK)
            print("Acm.RcvData failed:", rcode);

        for(uint16_t i=0; i < rcvd; i++) 
        {
            if (!ready && buf[i] == 2) { // 2 = start of data
                ready = 1;
                Serial.println();
                Serial.println("Ready to weigh...");
            }
            else if (buf[i] == 135)    // 135 = negative number
                data = "-";
            else if (buf[i] > 31 && buf[i] < 127)
                data += (char) buf[i];
            else if (ready && buf[i] == 13)
            {
                data += "                ";
                data += (char) buf[i];
                Serial.print(data);
                data = "";
            }
        }
        delay(10);
    }
    delay(10);
}