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EasyPic2 with on-board Ethernet Adapter

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Turn your EasyPic2 development board into an ENC28J60 Ethernet Toolkit

ENC28J60 Serial Ethernet ControllerThis page will show you how to connect your development board to the Ethernet Network, using the ENC28J60 Microchip Ethernet Controller.


You will be surprised to see how simple it is !

 

  The EasyPic2 : A good candidate for this enhancement

EasyPic 2 development board

This is my good old EasyPic2 development board from MikroElektronika. This is the one I fried one day... But it is still healthy and does a lot of good job. For those who don't know this board, here is a little review of its main features :

  • On-board USB fast programmer
  • DIP8 to DIP40 PIC sockets
  • 32 LEDs and 32 buttons, connected to I/O pins
  • 4 digits 7 segments LED display
  • Socket for 2x16 LCD text display
  • 2 trimmers for A/D conversion
  • 5 connectors, directly connected to I/O pins with pull-up/pull-down resistor arrays
  • RS232 adaptor and connector

What do we see bottom right ? Let's have a look closer...

 

 EasyPic prototype area 

There was space left on the board, so MikroElektronika had the good idea to make a prototype area for users.
210 plated-trough holes, both sides solder mask : until this day I never used this area.

 EasyPic prototype area (reverse side)

 

 

 

 

 

On the back side, we see that the upper row is connected to the +5V power line, and the lower row to the ground line.


Good ! Nature hates empty spaces isn't it ? Me too !

What do we need ?

ComponentsAlmost all that you need is on this picture. The heart of the circuit is the ENC28J60 Microchip Serial Ethernet Adapter, it is now widely available, and its DIP28 package is very convenient for prototyping.
Other important part is the 3.3V voltage regulator (transistor-like 3-pins plastic case on the picture) : the ENC28J60 can't operate directly with the +5V provided by the board.
The 25 Mhz crystal for ENC28J60 clock is easy to find at your usual supplier.
You will have also to find a magnetic for ethernet network (black rectangular box left to the RJ-45 socket), this one comes from an old ethernet hub board, as well as other parts seen on this picture. There are now RJ-45 sockets with integrated LEDs and magnetic, if you want to save more space on your board.

 

 

 

 


 

And now, go shopping :

Quantity Part # or value Type
1 ENC28J60 (Microchip) Serial Ethernet Controller
1 LP2950CZ-3.3 +3.3V voltage regulator
1 25 MHz crystal
1 Green LED
1 Red LED
1 10 F 25V capacitor
1 47 F 25V capacitor
2 10 nF capacitor
2 15 pF capacitor
1 100 nF capacitor
1 1 nF 2KV capacitor
4 50 Ohm 1% precision resistor
1 2.7 K 1% precision resistor
2 470 Ohm

resistor

1 FB2022 TX/RX magnetic filter
1 ferrite bead (value not critical) inductor
1 DIP 28 pins IC socket
1

RJ45

female solderable socket
1 2x5 pins connector + 5 jumpers used as switch

The circuit schematic

The circuit schematic comes from the datasheet of the ENC28J60 :
http://ww1.microchip.com/downloads/en/DeviceDoc/39662a.pdf
and its errata :
http://ww1.microchip.com/downloads/en/DeviceDoc/80257a.pdf

EasyPic Ethernet Adapter schematic

 

Click on the picture to enlarge the schematic

Please note that pin assignement of the TX/RX filter is not correct on this schematic due to lack of library for FB2022 transformer. You will have to refer to the datasheet of the part you will use (here is FB2022 datasheet)

 

 

As you can see, it is pretty simple :
The ENC controller is connected to the network through a magnetic adapter.
It needs a 25 Mhz crystal for its internal clock, resistors & capacitors for terminations, a 2.7K bias resistor, and a 10 F capacitor to stabilize its internal 2.5V power supply.
The controller can directly drive two programmable LEDs through current limitation resistors.
It is connected to the PIC through a 5 lines bus : reset line (RESET), chip select line (CS), SPI clock (CLK), SPI data input (SI), SPI data output (S0).
There are also 2 control lines that are not used in this exemple, but you can add them if you want, they are the interrupt line (INT) and the wake up on lan line (WOL). They can be used to trigger PIC interrupts, but in this example we operate using the polling method and we don't need them.

The most frequently asked question about this controler is the voltage level adaptation. The controller operates at 3.3V and the PIC on the board operates at 5.0V.
So, the question is : how to adapt ENC voltage levels to PIC voltage level ?


We must consider both sides :


PIC output voltage for logical 1 is 5V : does ENC accepts 5V on its inputs, whereas it is 3.3V powered ?
The answer is yes, ENC inputs are 5V compliant, so that there is no risk for the controller to apply 5V on its inputs, and they will correspond to logical 1.

ENC output voltage for logical 1 is 3.3V : will the inputs of the PIC turn high or low when 3.3V coming from the ENC outputs is applied ?
The answer is : it depends on the inputs of the PIC. TTL inputs give logical 1 above 2.05V, and will not require voltage level shifting. Schmitt trigger inputs give logical 1 above 3.5V, and will require voltage level shifting.

In fact, we can consider that if we connect ENC outputs to PIC TTL inputs only, the voltage level adapter is... a wire.
Most of PICs have TTL inputs and integrated SPI on PORTC, so we will connect all ENC line to this port.

Assembly


Prototype area with ethernet circuit

After soldering, you should get something that looks like this :

As you can see, I used a red/green bicolor LED instead of the two LEDs.

The jumper socket is placed just in front of the five lines that are connected to the PIC, so that removing the jumper isolates the ethernet circuit from the PIC, and PORTC can be used for other purposes.

The 3.3V regulator is mounted on a tulip socket : I have only one for now, and it is shared with another test board.

The 25 Mhz crystal is also mounted on a tulip socket, to save place for the two 15 pF capacitors hidden behind.

 

 

Ethernet protoype area, back side

 

 

I'm a little bit ashamed, but I show you the back side anyway. Sorry for the mess ;-)

Take care to respect the receive circuit polarity, because ENC is not able to detect it correctly due to a silicon bug. That's why I used color wires. If you connect it wrong, you may either have receive problem, or no receive at all.

 

 

 

Bus connected to PORTC

 

The bus is connected to the PORTC pins of the DIP28 socket.

Note that my cable deserves to be shortened...

 

 

 

 

 

 

Finally, this is what it looks like :

Front side Back side
EasyPic with Ethernet front side EasyPic Ethernet Back Side

 And now...

Testing the ethernet board with a source code example

It's time !

First, check and double-check all connections.
Don't plug the ENC28J60 in its socket, then power the board and verify the 3.3V power supply on each pin of the ENC.

Then turn the board off, put a 40 pins PIC as a PIC16F877A or a PIC18F452 in its socket, and clock it at its maximum speed.
Plug the ENC28J60 in its socket, and set the fiver jumpers to enable bus line between PIC and ENC.

Copy this mikroC source code and paste it in the mikroC compiler editor. If you don't have this PIC compiler already, download it for free now :
http://www.mikroe.com/en/compilers/mikroc/pic/download.htm

/*
 * file         : ep2enc28j60demo.c
 * project      : Ethernet controller ENC28J60 SPI communication test file
 * author       : Bruno Gavand
 * compiler     : mikroC V5.0.0.3
 * date         : july 26 2006
 *
 * description  :
 *      this code sets LEDA as link status display
 *      and makes LEDB blink permamently
 *
 * target devices :
 *      any PIC with integrated SPI on PORTC
 *      38 to 40 MHz clock is recommended to get from 8 to 10 Mhz SPI clock,
 *      otherwise PIC should be clocked by ENC clock output due to ENC silicon bug in SPI hardware
 *      tested with PIC16F877A@10Mhz, PIC18F452@40Mhz
 *
 *
 * EP2 settings :
 *      PORTC : pull-down
 *
 *      RC0 : !RESET    to ENC reset input pin
 *      RC1 : !CS       to ENC chip select input pin
 *      the ENC28J60 SPI bus CLK, SO, SI must be connected to the corresponding SPI pins of the PIC
 *      the INT and WOL signals from the ENC are not used
 *
 * see more details on http://www.micro-examples.com/
 *
 */

/*
 *  ENC SPI commands
 */
#define WCRCMD  0b01000000      // write control register
#define BFCCMD  0b10100000      // bit field clear
#define BFSCMD  0b10000000      // bit field set
#define BFCCMD  0b10100000      // bit field clear

/*
 * ENC SFR
 */
#define MIREGADR        0x14
#define ECON1           0x1f

#define PHLCON          0x14
#define MIWRL           0x16

/*
 * ENC PHY register
 */
#define MIWRH   0x17

/*
 * ENC CS control
 */
#define Select()         PORTC.F1 = 0
#define Deselect()       PORTC.F1 = 1

/*
 * 1 ms delay
 */
void    delay1ms()
        {
        Delay_ms(1) ;
        }

/*
 * writes byte v in ENC register addr of the current bank
 */
void    writeReg(unsigned char addr, unsigned short v)
        {
        Select() ;
        SPI_Write(WCRCMD | addr) ;
        SPI_Write(v) ;
        Deselect() ;
        }

/*
 * main entry
 */
void    main()
        {
        PORTC = 0 ;
        TRISC = 0b11111100 ;            // set PORTC as input except for bits 0 (RESET) and 1 (CS)

        Deselect() ;                    // don't talk to ENC

        SPI_Init() ;                    // init SPI communication, clock = Fosc / 4

        PORTC.F0 |= 0b00000001 ;        // reset = high
        delay1ms() ;                    // wait a little bit
        PORTC.F0 &= 0b11111110 ;        // reset = low, HW reset
        delay1ms() ;                    // wait a little bit
        PORTC.F0 |= 0b00000001 ;        // end of reset
        delay1ms() ;                    // wait for completion

        /*
         * set ENC memory bank 2
         */
        Select() ;
        SPI_Write(BFCCMD | ECON1) ;
        SPI_Write(0b00000001) ;
        Deselect() ;

        Select() ;
        SPI_Write(BFSCMD | ECON1) ;
        SPI_Write(0b00000010) ;
        Deselect() ;

        /*
         * set address of PHY register to write
         */
        writeReg(MIREGADR, PHLCON) ;

        /*
         * set LEDA for link status display
         * and LEDB for blink fast
         */
        writeReg(MIWRL, 0b10100010) ;
        writeReg(MIWRH, 0b00000100) ;
        }

Build the project and flash the .HEX into your PIC :

If LEDA is off and LEDB starts blinking, that's good news : the PIC can talk to the ENC controller through SPI communication.
If it does not, it should, check again your solderings & connections until it works.

Then connect your board to a hub with a straight cable : LEDA should now turn on with LEDB still blinking. LEDA on means that the adapter is correctly linked to the network. The network link LED of the other side hub should also turn on.

Congratulations, you have a wonderful ethernet development board for just a few boxes  !

Please report me bugs and aks questions in my forum

Last minute

If you don't want to bother with building your own serial ethernet board, this one by MikroElektronika is available :

http://www.mikroe.com/en/tools/serialeth/

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