[fpc-pascal] USB Human Interface Devices

Sat Aug 10 01:33:11 CEST 2019

Hi!

Am Freitag, den 09.08.2019, 08:08 -0400 schrieb James Richters:
> Hi Hansi,
> Thanks for the explanation.
>
> Here's the python code I’m trying to port over to FPC:
> https://github.com/wolfmanjm/kivy-smoothie-host/blob/master/modules/hb04.py
>
> it uses functions like hid.open, hid.close, hid.read, hid.write, and
> hid.send_feature_report   I'm trying to figure out how to somehow get
> similar functions to those in FPC.   Some example of how to perform
> those kinds of functions would be extremely helpful!

These hid.open, hid.close, ... functions are all methods of the object
"hid", which was previously assigned to from devices[0] (line 68),
which itself was returned from en.find(), where en is an object of
Enumeration() from the package easyhid.

To communicate with USB HID devices, please peek into the outdated
branch “master” of pas-libust (for legacy libusb-0.1) and open file
src/usb.pas. This is the old analogous to the new libusboop.pas.

It has the class TUSBPseudoHIDInterface which implements basic
communication with USB HID devices.

I've used that for a project with a barcode scanner. Please find
attached the two files snapi.pas (implementing the "standard" SNAPI for
barcode scanners, which is based on USB HID), and
barcodescannersymbolms4407.pas (implementing a few more specific
methods for a Symbol MS4407 barcode scanner). The latter file uses
several units of my project, therefore it will not compile on your
host. It is just to see how to use the SNAPI devices. I release these
files with the same license as libusboop.pas.

Please excuse that these files are still based on the outdated pas-
libusb for the old libusb-0.1. Therefore they would need translation
for the newer libusb-1.0 stuff. Unfortunately I've never head time to
transition the project. Actually you could copy the class
TUSBPseudoHIDInterface (plus the types THIDReport and TIntrReportFunc)
from usb.pas to libusboop.pas and change everything necessary.

At least one difference is that all names change from TUSB* to
TLibUsb*. I'm sure there are more, but I don't know by heart.

Please also excuse that I can’t recall why its just “PseudoHID” and not
a fully-fledged HID. Probably I didn’t implement all HID functions, or
the SNAPI HID interface just isn't registered with descriptor type $21.

This brings me to the second topic, where you got the message
  Unknown descriptor type $21 with length 9
from test2controlsync. That's a HID descriptor (see LIBUSB_DT_HID). It
is just not decoded in test2controlsync.

And finally, the third point regarding the bug with PortPath index.
I've fixed that now and pushed to Github. Thanks for pointing this out!

Thanks
  Hansi

> -----Original Message-----
> From: fpc-pascal <fpc-pascal-bounces at lists.freepascal.org> On Behalf
> Of Johann Glaser
> Sent: Friday, August 9, 2019 7:17 AM
> To: fpc-pascal at lists.freepascal.org
> Subject: Re: [fpc-pascal] USB Human Interface Devices
>
> Hi!
>
> Just a quick reply while at work, I'll reply to all EMails in the
> evening.
>
> First of all: Thanks for finding the bug with the index variable I
> vs. J. I'll fix that in the evening.
>
> Secondly: You are correct, the "EZ-USB" is a specific chip family by
> Cypress, e.g., AN2131, without Flash/ROM but with SRAM for the
> firmware. I built a few devices with that chip, therefore I also
> implemented the Pascal "driver" to download the firmware into the
> "naked" device. There are also many (old) devices on the marked which
> use that chip, e.g., the Keil uLink (1st generation).
>
> To understand how USB actually works (endpoints, in and out
> transfers, control/bulk/interrupt/isochronous transfers, ...), I have
> learned a lot from the Technical Reference Manual (TRM) of the EZ-
> USB. Just search for it, there are plenty of sources. Chapter 1 is
> the interesting one. If you directly search at the Cypress page, they
> will redirect you to the successor product FX2, but its chapter 1 is
> nearly identical to that of EZ-USB.
>
> The EZ-USB firmware download is performed with control transfers to
> EP0. So you can find examples for control transfers in ezusb.pas.
>
> You can find example code for bulk and interrupt endpoints e.g., in
> https://github.com/hansiglaser/pas-gpib/blob/master/usb/usbtmc.pas.
>
> I can provide more examples in the evening.
>
> Bye
>   Hansi
>
> > Gesendet: Freitag, 09. August 2019 um 12:09 Uhr
> > Von: "James Richters" <james at productionautomation.net>
> > An: "'FPC-Pascal users discussions'" <
> > fpc-pascal at lists.freepascal.org>
> > Betreff: Re: [fpc-pascal] USB Human Interface Devices
> >
> > Maybe I am going down the wrong path trying to get
> > test_arduino_with_bmp280.pas to work with my device...  I think I
> > am confusing easyusb with easyhid which is what is used to
> > communicate with the device in the python code I am trying to
> > use.  It looks like easyusb is to send firmware to a specific usb
> > device that has no rom in it... and that's not exactly what I'm
> > trying to do...
> >
> > I'm trying to figure out how to open the device and read data and
> > write data to this device.  Is there an example of how to do that
> > with pas-libusb?
> >
> > Sorry I am so confused by all this.  I feel like I'm almost to
> > where I will understand things again but I'm just missing
> > something.
> >
> > James
> > _______________________________________________
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> >
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