USB CDC Communications for Dummies!

[ricgar]

Hi Guys

I'm pretty new to all of this, but here's my attempt.

I've attached a schematic of the device i am using.

What i am attempting to make here is some sort of USB to Serial Port Converter.

The code i loaded onto the chip is as follows:

'****************************************************************
'*  Name    : UNTITLED.BAS                                      *
'*  Author  : [select VIEW...EDITOR OPTIONS]                    *
'*  Notice  : Copyright (c) 2009 [select VIEW...EDITOR OPTIONS] *
'*          : All Rights Reserved                               *
'*  Date    : 2009/01/02                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************
@   __CONFIG	_CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@	__CONFIG	_CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
'_CONFIG1H, _FOSC_XTPLL_XT_1H 
@	__CONFIG	_CONFIG2L, _PWRT_ON_2L & _BOR_ON_2L  & _BORV_28_2L  & _VREGEN_ON_2L
@	__CONFIG	_CONFIG2H, _WDT_OFF_2H
@	__CONFIG	_CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H & _CCP2MX_ON_3H
@	__CONFIG	_CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L

' ****************************** Configure Hardware *********************************************
trisb = %11111100
trisc = %10111111       	' Set TX (PortC.6) to out, rest in
spbrg = 25            		' Calculate ((CPU speed mhz/Baud)/16)- 1  25 = 115200 baud  EX:((48000000/115200)/16)-1
rcsta = %10010000       	' Enable serial port and continuous receive
txsta = %00100000       	' Enable transmit and asynchronous mode/brgh = 0 bit 2
baudcon =%00001000			' Bit3 = 1: High speed usart 16 bit  

'***************************** Variables ******************************************
USBBufferTX Var Byte[1]
USBBufferRX var Byte[1]
USBBufferCount Var Byte
SerBufferTX Var Byte
SerBufferRX var Byte[1]
BufferRX var Byte
SerBufferCount Var Byte
Indexer var byte
Xmit_Start var bit									' Start serial data transmission
Status_Bits var byte								' Status bits to Pc
Data_Delay var word									' Delay for dataout
Data_Out var word									' Data 

Status_Bits = 0

LED	Var	PORTB.1

Define  OSC     48

	USBInit
	high led
	pause 1000
	Low LED		' LED off
    USBService

    for Indexer = 0 to 0
	   USBBufferRX[Indexer]= 0
    next

    usbbuffercount = 1
    
    
main:
    goSUB usb_rx
    goSUB com_rx
goto main    

	' Transmit USB Data     
USB_TX:
					' TX buffer size
USBService 
USBOut 3, serBufferrX, USBBufferCount, main 			' Transmit data		
RETURN

	' Receive USB Data 
USB_RX: 
USBService 											
USBIn 3, USBBufferRX, USBBufferCount, exitsub 		' Receive data if available,then exit
serbuffertx=usbbufferrx[0]
goSUB com_tx
return
'GOSUB Main


'Serial Receive

COM_RX:
hserin 1, exitsub, [bufferrx]
serbufferrx[0]=bufferrx
goSUB usb_TX
goSUB main

'Serial Transmit
COM_TX:
hserout [serbuffertx]
RETURN

exitsub:
return

Now this code compiles and i can connect via a hyperterminal to both the USB virtual and the physical Serial port. However if i enter anything in either of hyperterminals, it gives nothing and after a while of constant typing the hyperterminals start freezing on me. So i take it i've done something horrifically wrong.

Any suggestions?

[mister_e]

this section

COM_RX:
hserin 1, exitsub, [bufferrx]
serbufferrx[0]=bufferrx
goSUB usb_TX
goSUB main

I guess you want a Return there.

And when you deal with HSEROUT/HSERIN, you should use DEFINEs, unless, it will use default 2400 Bauds baudrate.

AND you must add DEFINE OSC 48 at the top of your code as well.

That should be enough to start

[ricgar]

Hi Mister_e

Thanks for the response. I did already have a DEFINE OSC 48 already near start of the code, i have changed it to be return instead of GoSub Main. Thanks. As for your quote below

this section
you should use DEFINEs, unless, it will use default 2400 Bauds baudrate.

Would you be able to provide a bit more detail as regards the DEFINEs you mention, i have no clue what you mean by that.

Thanks

[mister_e]

DEFINE for HSEROUT are explained in the PBP manual

The serial parameters and baud rate are specified using DEFINEs:

' Set receive register to receiver enabled
DEFINE HSER_RCSTA 90h

' Set transmit register to transmitter enabled
DEFINE HSER_TXSTA 20h

' Set baud rate
DEFINE HSER_BAUD 2400

' Set SPBRG directly (normally set by HSER_BAUD)
DEFINE HSER_SPBRG 25

HSEROUT assumes a 4MHz oscillator when calculating the baud rate. To maintain the proper baud rate timing with other oscillator values, be sure to DEFINE the OSC setting to the new oscillator value.

In your case, the DEFINE list would look something like

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 25  ' 115200 Baud @ 48MHz, 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

HTH

[davids]

DEFINE OSC 48

Buffer VAR BYTE[16]
Cnt VAR BYTE
B0 VAR BYTE
B1 VAR BYTE
led var porta.3

ADCON1 = 15 ' Set all I/Os to Digital
CMCON = 7 ' Disable Comparators
Cnt = 16

USBInit ' Initialize USART
start:
for b0 = 0 to 15
lookup b0,["USB CONNECTED!",10,13],B1
BUFFER(B0) = B1
NEXT B0
gosub send
ledl:
high led
pause 1000'(when i have delay nothing is working)
low led

afterled:
for b0 = 0 to 15
lookup b0,["closed led",10,13],B1
BUFFER(B0) = B1
NEXT B0
gosub send
goto start

send:
USBService ' Must service USB regularly
USBOut 3, Buffer, Cnt,send
return
end

[davids]

everything is working perfect i have connect it with labview but when i am using PAUSE 1000 nothing is working !!!!!!!

[ScaleRobotics]

Its the:

USBService ' Must service USB regularly

part. It must be serviced every 10 ms, or your communication will drop. So your pause 1000 is about 100 times too long. Some people have used Darrel's interrupt routines for the service interval. Here is one link:

http://www.picbasic.co.uk/forum/show...5302#post45302