On Mon, 28 Feb 2011 22:12:37 -0600, Марко Краљевић krasnaya.zvezda@gmail.com wrote:
On Mon, Feb 28, 2011 at 17:08, Joseph Smith joe@settoplinux.org wrote:
This is probably pretty pokey? I was thinking of making something similar with an AVR. I can't seem to find much information on speed capability of USB CDC / ACM devices though? If they only support 115k or whatnot as the top end, it'll be pretty painful, I'd think.
curious.
I was looking at some of the UBW tutorials and it appears you can set the baudrate to pretty much what ever you want. It is set in the PIC's "bootloader" / firmware and of course your PC (that is what you mean by 115k correct?). The PIC18 runs at 48 MHz. There is also a UBW32 project that runs a PIC32 at 80 MHz but I am not sure if that would be a overkill and it costs more. Any ways there are sparkfun modules for both versions and the PIC18 chip itself only goes for around $6-7 dollars. I just think it is really cool that the UBW was orriginally designed as a parallel replacement for bit-banging over USB-> serial. I think it would be very easy to add flashrom support for this device and there is enough GPIO's on the PIC18 so you could support both LPC/FWH and SPI on the same device. I also like how "open" Microchip is with their products :-)
Anyways I don't know alot about PIC devices but I thought I would throw it out there that it seems like 75% of the work has already been done on the UBW to make it a neat little cost effective external USB flashrom programmer.
On Tue, 01 Mar 2011 04:01:59 -0500, Joseph Smith joe@settoplinux.org wrote:
On Mon, 28 Feb 2011 22:12:37 -0600, Марко Краљевић krasnaya.zvezda@gmail.com wrote:
On Mon, Feb 28, 2011 at 17:08, Joseph Smith joe@settoplinux.org wrote:
This is probably pretty pokey? I was thinking of making something
similar
with an AVR. I can't seem to find much information on speed capability
of
USB CDC / ACM devices though? If they only support 115k or whatnot as the top end, it'll be pretty painful, I'd think.
curious.
I was looking at some of the UBW tutorials and it appears you can set the baudrate to pretty much what ever you want. It is set in the PIC's "bootloader" / firmware and of course your PC (that is what you mean by 115k correct?). The PIC18 runs at 48 MHz. There is also a UBW32 project that runs a PIC32 at 80 MHz but I am not sure if that would be a overkill and it costs more. Any ways there are sparkfun modules for both versions and the PIC18 chip itself only goes for around $6-7 dollars. I just think it is really cool that the UBW was orriginally designed as a parallel replacement for bit-banging over USB-> serial. I think it would be very easy to add flashrom support for this device and there is enough GPIO's
on
the PIC18 so you could support both LPC/FWH and SPI on the same device. I also like how "open" Microchip is with their products :-)
Anyways I don't know alot about PIC devices but I thought I would throw
it
out there that it seems like 75% of the work has already been done on the UBW to make it a neat little cost effective external USB flashrom programmer.
I also found this under the FAQ's:
Q: How fast is a UBW? A: That question is somewhat ambiguous. I'll answer the question I _think_ you're asking: how many bytes/second can I pump down to the UBW? That depends upon what USB "Class" the firmware you are using implement. The maximum theoretical speed of these PIC USB parts is 12Mb/s (mega-bits per second). With Firmware C, I get about 500 to 800 Bytes/second to come out Port B pins. With a custom firmware I wrote for a client, I've gotten over 20K Bytes/second. If somebody develops a firmware based upon Microchip's Mass Storage Class driver, or their Custom Driver, then it should be able to reach 100K bytes/second if not more. Oh, and the RC oscillator on the UBW runs at 4 MHz (or 20MHz for SparkFun version), and the internal PIC PLL bumps that up to 96MHz, then divides down to 48MHz to run the USB engine and the PIC core. Which means that these boards run at 12MIPS (because Microchip has a divide by 4 on their core clock.) A2: If you are looking for Fosc speed on all UBWs, it is 48MHz.
Q: Does it matter what baud rate I choose when I open the COM port to the UBW? A: Nope. It doesn't. There really is no 'serial' link between the PC and the UBW. It is all through USB. USB does not have a 'baud rate' feature in the traditional sense of RS-232. The USB host chip on the PC schedules the bus transactions as quickly as it can, abiding by all of the protocol rules that define USB. (i.e. no fixed baud rate) In a traditional USB to RS-232 converter product, the PC sends 'baud rate change' messages to the converter chip, which then re-programs its RS-232 clock rate for sending/receiving async serial data. The UBW does not currently have a true RS-232 capability, so these messages are simply ignored by the UBW firmware. The UBW simply uses the part of this standard USB RS-232 converter setup to the point where there is a getchar() and putchar() function in the software of the PIC. The UBW does not then actually send that data out its serial port. (It could, if one wanted to, but does not at this point in time - FW D 1.4.2) Instead, it reads the data coming from the PC and processes that data as commands. Thus, it makes no difference to the UBW what baud rate or data bits or parity you use. HOWEVER - it does matter if you select hardware handshaking. Why? Because your terminal emulator may wait until certain handshake lines are asserted before sending data down to the UBW. Since the UBW does not implement any of the handshaking lines, this will never happen and your UBW will appear to be dead. So make sure you DISABLE or turn off any hardware handshaking. Don't use software handshaking either - always set it to 'off' or 'none'.
-
Joseph Smith