It is very easy task to do this with microC and VB.NET for example. I did it many times. I'll try to help you. I made USB Joystick based on CDC-decoder (capacitor sensors).
But you will have to wait a little because all compilers and simulators installed only on my work laptop. And I forgot them in office. Please, be patient. I promise to help you.
---------- Post added 01-12-11 at 00:24 ---------- Previous post was 30-11-11 at 23:59 ----------
So, I can use my second laptop a little and we can start. Sorry for my english.
First of all, we need to start new project and choose a micro controller. I'm using PIC18F1xK50.
It is very low cost controller. But I must warn you. It not support debug functions.
You can choose PIC18F13K50, it support USB too, but it has two time less ram and flash memory. Flash memory not a problem. But after using HID Library you will able to use less then 20% free ram memory. Use this controller only with very simple tasks if you want to use USB HID.
So, we choosing PIC18F14K50.
To be continued...
Few words about clock frequency. For USB2.0 USB clock must be very accurate 48Mhz. Only high speed (HS) crystal accepted. You can use 6,12,24 and 48 Mhz crystals. We will use 12Mhz crystal with 4xPLL.
---------- Post added at 00:36 ---------- Previous post was at 00:24 ----------
Let's continue...
After the project wizard closed, we need to adjust configuration bits.
CPU System clock Selection
We can choose dividing main clock. For example, if we are using 24Mhz crystal, to obtain 48Mhz main clock frequency, we need to divide it by 2 and then use 4xPLL multiple.
MCLR Pin
Usually, I'm turning off this pin to provide digital functions on it. If you not using external watch dog or don't want to use reset chain, turn it off and let the MCU reset him self.
All other settings look understandable clear.
---------- Post added at 00:40 ---------- Previous post was at 00:36 ----------
Ok, the project ready. Let's start to use the library.
Lunch HID Terminal
Tools -> HID Terminal
Choose
Descriptor page.
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VID and
PID - you device individual numbers. If you want to use it officially, you should prepare two thousand dollars for registration. Don't try do this in real life. You will be killed or seriously injured by your wife.
This numbers stored in HEX format. So, VID=0x2233 and PID=0x2005 for our example. We will use this values on PC part.
Report length - number of bytes that we will send to PC and read back.
Bus power - maximum current consumption that we able to use in our circuit in case of USB Power. Useful for USB Li-Ion chargers for example.
Endpoints pooling int.
Very important thing. I will explain how to use it for advanced users. Now we just leave it for 1 msec.
Vendor and
Product name.
Write here what you want. This string you will see when the device will be connected to PC.
So, we are finished with descriptor. Lest save it in project folder and add this file to project.
---------- Post added at 00:51 ---------- Previous post was at 00:49 ----------
Now we are ready to prepare our first program. Just use copy-paste my code. I will explain how it works.
Code:
unsigned char readbuff[8] absolute 0x280; // Buffers should be in USB RAM, please consult datasheet
unsigned char writebuff[8] absolute 0x288;
void main() {
char cnt;
ANSEL=0; // CONFIGURE ALL PORTS FOR DITITAL I/O
ANSELH=0; // NEVER DO THIS IN REAL LIFE. UNUSED PINS MUST BE LEFT ANALOG INPUTS
HID_Enable(&readbuff,&writebuff); // Enable HID communication
while(1)
{
while(!HID_Read());
for(cnt=0;cnt<8;cnt++)
writebuff[cnt]=readbuff[cnt];
while(!HID_Write(&writebuff,8));
}
}
void interrupt(){
USB_Interrupt_Proc(); // USB servicing is done inside the interrupt
}
---------- Post added at 00:59 ---------- Previous post was at 00:51 ----------
Now I will explain what this code do and how.
Code:
unsigned char readbuff[8] absolute 0x280; // Buffers should be in USB RAM, please consult datasheet
unsigned char writebuff[8] absolute 0x288;
We declaring to local byte arrays for input and output data. As you can see, the array length is the same like in descriptor (8 bytes). This is mandatory.
What does 0x280 and 0x288 means?
It is absolute address for store the usb data. To use the correct adress, we need to explore the datasheet (always read datasheets. It is like a bible for embedder!)
The datasheet says that the USB RAM starts from address 0x280 and ends at 0x2FF. That means that we have 127 bytes for store the input and output data. Thats why you can't use array longer than 64 bytes.
Because our readbuff array 8 bytes long, we should use memory for writebuff starts from 0x288 address.
---------- Post added at 01:01 ---------- Previous post was at 00:59 ----------
Now we can connect our device to PC.
VDD -> USB VCC
D+ -> USB D+
D- -> USB D-
VSS - USB GND
Or we can simulate it with Proteus with USB drivers installed. No difference. It will work too.
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After that we have a new device connected. Should I explain how to write and read data in program?
If you want to use interrupts, I will explain how to separate it from USB Pooling Interrupt later. I need to find my examples.
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Special for moderators.
If you want that I continue this article, please, store my messages in FAQ or etc.
See in next series...
USB Joystick. It is easy!
Getting data from device using VB.NET
Transferring data from any pointer device to microcontroller throw radio transceiver. First step to build radio-controlled robot.