Archive for the ‘Micro controllers’ Category

PIC 16F877 prototyping board – part 2

July 15th, 2008 Comments off

A low cost PIC 16F877 prototyping board is being developed at College of engineering Attingal under my guidance. The credit for develoment goes to Shibu and Manoj. The board is intended for classroom use. The idea is to provide a low cost platform for experimenting with PIC micro controllers. The proposed board will have easily attachable daughter boards for connecting various accessories such as key board, LEDs , switches etc. The board will be programmable via serial port through an ICSP programmer.

The first draft schematic of the board is give below. This board contains a PIC 16F877 and ICSP programmer interface. All ports of the PIC are available via FRC connectors.


The PCB pattern along with component lay out for building the board is shown below.


You can download a PCB pattern suitable for homebrewing can be found here.

We have just completed the first board and pictures of the same are provided below.

pic_prototype_board pic_protype_board1

Building a PIC 16F877 prototyping board-Part1 Programmer

March 25th, 2008 1 comment

I have been trying to develop a general purpose prototyping board for the Microchip PIC 16F877A . My aim is to build a board with the following features

a) All ports and other on board devices must be easily taken out to a solderless bread board.

b) In circuit serial programming.

c) boot loader.

d) the board will have some switches , an LCD module , a few LEDs and a pot for analog input simulation.

My design is almost complete. In fact, there is nothing new in the design. I have done cut and paste from several circuits.

I am planning to post schematics and experiences while building the board on this blog.

Today, I have completed the in circuit serial programming module(ICSP). This is based on this article by Ian Lesnet.My final prototype is shown below. The pcb layout for home brewing via toner transfer method is here.

The original article uses a PCB mounted 9 pin D connector. I I found it inconvenient ,after soldering the board. Instead , Ifixed a piece of ribbon cable. My programming set up is shown below. Just wire the connectors to the appropriate pins.


The board lacks any indicators. I am planning to redesign the pcb with 2 indicator LEDs later.

The software I used is winpic800 . It works like a charm. ( The default interface is in Spanish, change it to english by selecting Idioma->English in the main menu)

Categories: Electronics, Micro controllers Tags:

Option Technology Globe Trotter PCMCA card on Debian GNU/Linux

January 30th, 2008 Comments off

My friend, Ramakrishnan VU2KUC, has been asking me to install necessary drivers for his Option Technology Globe Trotter PCMCA card on Debian Linux. I think he has made at least 20 phone calls for same. This morning he brought his Compaq laptop to my home and asked me to fix it. I had no other choice left.
I made a google search and found that Option does not officially support Linux. But they gave me a link
which gave a general outline.
The actual driver for this GPRS modem is at
(Later on I found out I can apt it as apt- get install gcom)
The man page of comgt/gcom is very informative.
I inserted the card. It was recognized as a modem at ttyS2

pccard: PCMCIA card inserted into slot 0
pcmcia: registering new device pcmcia0.0
0.0: ttyS2 at I/O 0×3e8 (irq = 3) is a 16550A

I made a link to /dev/modem

#ln /dev/ttyS2 /dev/modem

Then installed wvdial and ran wvdialconf, which created a basic wvdial.conf in /etc/
# apt-get install wvdial

I tweaked /etc/wvdial.conf as below

[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Init3 = AT+CGDCONT=1,”IP”,””
Modem = /dev/modem
Phone = *99***1#
Idle Seconds = 3000
Password = dummy
Modem Type = Analog Modem
Stupid Mode = 1
Compuserve = 0
Baud = 115200
Auto DNS = 1
Dial Command = ATD
Ask Password = 0
ISDN = 0
Username = dummy

“ ” is the APN, which you have to obtain from your service provider.
Then I did
# gcom -d /dev/ttyS2

SIM ready
Waiting for Registration..(120 sec max)
Registered on Home network: “CellOne”
Signal Quality: 15,99

This registered the SIM to the BSNL ( local provider) network

I tried to dial into the BSNL network

The modem connected to the Internet and I could browse.
But after 2 minutes the connection dropped suddenly. This happened several times. I examined the log and found this error message

The PPP daemon has died: Lack of LCP echo responses (exit code = 15)
–> man pppd explains pppd error codes in more detail.

It seems the gprs modem is handling the LCP request properly. I edited the /etc/ppp/peers/wvdial as below and disabled LCP echo failure

name wvdial
lcp-echo-failure 0
lcp-echo-interval 0

Now the connections stays even after 2 minutes.

VU2KUC is a happy man. :)

Categories: Gnu/Linux, Micro controllers Tags: