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cenadius
Joined: 13 Mar 2010
Posts: 11
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| USB transmission must do it in "int8"? |
 Posted: Sat Mar 27, 2010 10:40 pm |
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Hi, I want to send a string and a float through usb to my computer GUI, and I find out that usb_put_packet() function must transmit data in int8.
Below is my code:
| Code: |
include <18F4550.h>
#fuses HSPLL,USBDIV,PLL5,CPUDIV1,VREGEN,NOWDT,NOPROTECT,NOLVP,NODEBUG
#use delay(clock=48000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
#define USB_HID_DEVICE FALSE
#define USB_EP1_TX_ENABLE USB_ENABLE_BULK //turn on EP1(EndPoint1) for IN bulk/interrupt transfers
#define USB_EP1_RX_ENABLE USB_ENABLE_BULK //turn on EP1(EndPoint1) for OUT bulk/interrupt transfers
#define USB_EP1_TX_SIZE 2 //size to allocate for the tx endpoint 1 buffer
#define USB_EP1_RX_SIZE 33 //size to allocate for the rx endpoint 1 buffer
// Include the CCS USB Libraries. See the comments at the top of these
// files for more information
//
/////////////////////////////////////////////////////////////////////////////
#include <pic18_usb.h> //Microchip PIC18Fxx5x Hardware layer for CCS's PIC USB driver
#include <fypusb.h> //USB configuration and descriptors
#include <usb.c> //handles usb setup tokens and get descriptor reports
#define modeo dataout[0]
#define conv dataout[1]
void main(void)
{
int8 datain[33];
int8 dataout[33];
usb_init(); //init USB
usb_task(); //usb interrupt
usb_wait_for_enumeration(); //wait from host PC
while (TRUE)
{
if(usb_enumerated()) //usb config
{
if (usb_kbhit(1)) //
{
usb_get_packet(1, datain, 64); //
modeo = 0;
conv=111.99;
usb_put_packet(1, dataout, 2, USB_DTS_TOGGLE);
}
}
}
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For my GUI, I will receive 111 only, I can't get 111.99. I realise that the problem might be cause by the "int8 dataout[33]" declaration. I had tried to declare it with "float dataout[33];", but the transmission failed.
Can someone guide me in how to make the usb transmit a float or string to computer?
Thank you. |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Sun Mar 28, 2010 3:20 am |
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The problem hasn't to do with USB at all. You just have to learn some C-programming basics. The first point to consider
is that float has a length of four byte. So if you need an int8 array to represent a float variable, it must have a
length of 4 at least.
There are various methods to copy the content of a float variable to an int8[4] array. It's a serial topic at ccs forum,
because it's needed for different purposes, e.g. transmitting the data on RS232, storing to an EEPROM and much more. A
generic C method is by using unions, CCS C has the make8() and make32() built-in functions to copy larger data
units to int8 and vice versa. |
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