PIN-Out of connector
Q: What signals are assigened to the six contacts at the lower edge of the PCB?
1 VPP/RA3 (Square pin) 2 VDD 3 GND 4 ICSPDAT/RA0 5 ICSPCLK/RA1 (also connected to touch sensor) 6 PGM (seems to be unconnected)
Hardware requirements for reprogramming
Q: What minimal hardware (cable, programmer etc.) is required to reprogram the PIC?
A: Any PIC programmer will do. The core OpenBeacon developers are using PICkit 2 from Microchip. But there are even cheaper ones, and you can also build them yourself (http://www.jdm.homepage.dk/newpics.htm)
Software requirements for reprogramming
Q: Is it possible to use the PICkit 2 Microcontroller Programmer for programming a Sputnik tag from Linux?
A: Yes: See our explanation of the Linux Installation Process of Microchip development environment
Q: Can the PIC also be reprogrammed with open source software like SDCC?
A: Yes. The specific PIC that we use is supported. This is a matter of updating compiler specific code to make it work in SDCC.
Tag as base-station
Q: What is the best way to connect a tag to a PC in order to use it as a base station?
A: You would have to do a software implementation (bit-banging) of the RS232 protocol, use the RA0/RA1 pins on the header for it and connect a 3V-to-RS232 level shifter (commonly found with embedded projects, such as OpenWRT, etc.)
The following links might be helpful for doing a RS232 software implementation:
- German Mikrocontroller Forum -- mit PIC 16f877 seriell daten senden und empfangen
- Microchip Application Notes AN510 Implementation of an Asynchronous Serial I/O
- Microchip Application Notes AN593 Serial Port Routines Without Using Timer0
Using IO Pins
Q: Which IO pins can be used for own purposes (RA0/1/3?)? Are there any restrictions to keep in mind?
Tag as a mesh router
Q: Would it be possible to build some kind of meshed network based on those tags? Shurely the controller has toolittle memory to do TCP/IP, but would some simpler protocoll be possible?
A: The academic community working on wireless sensor networks (WSN) has developed quite a few protocols for multi-hop networking with similar devices (wiresess sensor nodes, mostly based on Atmega128 and TI MSP430 and similar trancievers). One of the central goals of WSN routing algorithms is to achieve reliable transmissions despite a constantly changing network topology, interferences etc. with a minimum of costly (in terms of energy consumption) retransmissions.