USB to RS232 adapter

[Darrel Taylor]

That was pretty quick!

I've been playing with the program here and can say that the two PAUSE 25 statements, have to GO.

Of course that messes up the LED's, but with the pauses in there, it only picks up every 7 or 8th character when sending continuous data.

Without them, it works pretty good, but it's still a bit slow.
Test data of about 1500 bytes takes nearly 3 times as long as it should. Around 1.2 sec.

I think circular buffers would help speed it up, since it has to wait till it's finished sending the HSEROUT before in can receive more data from the USB. But I guess that depends on how fast you need it to be.

[PJALM]

Thanks Darrel. I have eliminated the LEDs all together because there is really no need for them. I was testing it by just using a terminal program on 2 computers so I never noticed the speed problem till now. How do I impliment the circular buffers you mentioned?

[Darrel Taylor]

Me and my big mouth.

I wish I had time to work something up, but I've got too many things going on already.

You might take a look at this post by Joe S.
http://www.picbasic.co.uk/forum/showthread.php?p=28233

He's got a buffer in there for serial RX. Should give you a start.
But you really need to buffer both RX and TX.

busy busy,

[Squibcakes]

Hi Guys I've been working on the same - I can get a Half duplex data communication going but not full duplex (rs232-> usb and vice versa).

This program seems to do the trick, but even with the pauses removed I still only achieve a stable data rate at 9600 when sending large text files.

I'll try using the DT method (DT_int_18) interrupts and see if this speeds things up.

Circular buffers? The mind boggles!

Cheers

[mister_e]

i doubt it would be if you used the EUSART but may worth to try..

PicMultiCalc gaves me...

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 225 ' 9600 Baud @ 48MHz, 0.0%
SPBRGH = 4
BAUDCON.3 = 1         ' Enable 16 bit baudrate generator

mixing INT_18 and asm would certainly have some great effect.

[Darrel Taylor]

I can get a Half duplex data communication going but not full duplex

USB is a Half-Duplex protocol. There's no way to have TRUE full-duplex. 2-wires, differential levels, can only do one thing at a time.

However, with the proper buffers in place, you can make it seem like it's "FULL", in that you can send and receive at the same time from the USART. But it never truely will be Full-duplex for the USB.

[Squibcakes]

Yeah your right,

I guess what I should have said was this.

I can transmit in only one direction usb->usart, or usart->usb, not in the same program. Never mind now. I'm confused... ;(

Using Int_18 has def. sped things up!

Now I can transfer from USB->Usart successfully at 57600 baud, however Usart->Usb still only good enough at 9600 when sending text file. (Sending single key strokes is fine both directions at any speed).

I figure that the usart buffer needs to be increased as this is the bottle neck.


Cheers