Hi all,
I'm trying to use my Arduino Mega to communicate with a light meter. Basically I need to send a serial command to the light meter so that Arduino can receive and read the measured data. I add a USB host shield and connect it with the light meter using USB cable.
However, it seems like the USB communication is much harder than RS232 communication. The device needs a FTDI driver as described in the Communication Specification(attached), meaning that I need to write a driver by myself. I found there is a FTDI Sketch Example included in the USB shield library, but I have no idea how it works and how should I modify it since I can't find any detailed explanation regarding this issue. As described in page 31 of the attached manual (communication method), the character length is 7 bits; Even Parity; 1 stop bit. So it is necessary to modify these parameters. Can anyone teach me how can I do that? Any help would be appreciated. Thank you so much.
Here is the Sketch included in the USB shield library:
#include <cdcftdi.h>
#include <usbhub.h>
#include "pgmstrings.h"
// Satisfy the IDE, which needs to see the include statment in the ino too.
#ifdef dobogusinclude
#include <spi4teensy3.h>
#endif
#include <SPI.h>
class FTDIAsync : public FTDIAsyncOper
{
public:
uint8_t OnInit(FTDI *pftdi);
};
uint8_t FTDIAsync::OnInit(FTDI *pftdi)
{
uint8_t rcode = 0;
rcode = pftdi->SetBaudRate(115200);
if (rcode)
{
ErrorMessage<uint8_t>(PSTR("SetBaudRate"), rcode);
return rcode;
}
rcode = pftdi->SetFlowControl(FTDI_SIO_DISABLE_FLOW_CTRL);
if (rcode)
ErrorMessage<uint8_t>(PSTR("SetFlowControl"), rcode);
return rcode;
}
USB Usb;
//USBHub Hub(&Usb);
FTDIAsync FtdiAsync;
FTDI Ftdi(&Usb, &FtdiAsync);
void setup()
{
Serial.begin( 115200 );
#if !defined(__MIPSEL__)
while (!Serial); // Wait for serial port to connect - used on Leonardo, Teensy and other boards with built-in USB CDC serial connection
#endif
Serial.println("Start");
if (Usb.Init() == -1)
Serial.println("OSC did not start.");
delay( 200 );
}
void loop()
{
Usb.Task();
if( Usb.getUsbTaskState() == USB_STATE_RUNNING )
{
uint8_t rcode;
char strbuf[] = "DEADBEEF";
//char strbuf[] = "The quick brown fox jumps over the lazy dog";
//char strbuf[] = "This string contains 61 character to demonstrate FTDI buffers"; //add one symbol to it to see some garbage
Serial.print(".");
rcode = Ftdi.SndData(strlen(strbuf), (uint8_t*)strbuf);
if (rcode)
ErrorMessage<uint8_t>(PSTR("SndData"), rcode);
delay(50);
uint8_t buf[64];
for (uint8_t i=0; i<64; i++)
buf[i] = 0;
uint16_t rcvd = 64;
rcode = Ftdi.RcvData(&rcvd, buf);
if (rcode && rcode != hrNAK)
ErrorMessage<uint8_t>(PSTR("Ret"), rcode);
// The device reserves the first two bytes of data
// to contain the current values of the modem and line status registers.
if (rcvd > 2)
Serial.print((char*)(buf+2));
delay(10);
}
}