PIC-based temperature logger with onboard storage


Last summer, [Rajendra Bhatt] built himself a simple PIC-based temperature monitor with data logging abilities and recently got around to sharing it on his site. The sensor is based on a PIC12F683 micro controller and measures the ambient temperature on a set interval, storing the values on the MCU’s internal EEPROM.

He used a Maxim DS18B20 temperature sensor, which communicates with the PIC over a 1-wire bus. The sensor is read based upon the interval chosen by the user, and can be configured to measure the temperature every second, every minute, or every 10 minutes. The data is stored on the aforementioned EEPROM and can be uploaded to a computer via a serial connection. The PIC has the ability to store 254 readings before the data must be cleared from the device.

It’s a great beginner project, and has plenty of room for improvement. As [Rajendra] points out, an external EEPROM could be added to expand the recording capacity, and it would be nice to have a real-time clock on hand for accurate time stamping. If we were to build one ourselves, a means of wireless data transfer would be first on our list of potential enhancements.

Propeller Platform prototyping board gets an upgrade

[Nick] over at Gadget Gangster has a new version of his prototyping hardware for Propeller microcontrollers, called the Propeller Platform USB. A little more than a year ago we looked at the last version which was larger, used a DIP processor, and came unassembled. The new version does come assembled because of the migration to surface mount components (which may take some of the fun out of it if you just love soldering kits). This not only reduces the board footprint, but makes room for more goodies. As the name implies, there’s now a mini-USB socket with a USB to UART bridge, a microSD card slot as been added, and the onboard EEPROM has been doubled. This is a nice hardware upgrade but the price has been upgraded by $25 as well. No worries, it’s open source so you can roll your own if you have the parts on hand.

Porting code to MSP430

I took a little time to look into porting code written for AVR in order to run it on the MSP430 architecture. It’s easier than you think, being mostly small differences like an extra step to enable pull-up resistors. But there is a lot to be learned in order to transition away from using EEPROM.

Since the TI chips don’t have EEPROM you need to use the Info Flash, a topic which I detail in the article linked at the top. This flash memory must be erased before writing because a write operation can only change high bits to low, not the other way around. And an erase operation clears an entire 64 kB segment, not just the bytes you want to write to. It’s different but manageable.

Oh, and if you were wondering, I ported the code I wrote for the garage door coded entry project.

Unbricking with the help of Arduino


This bricked Eee PC came to [Janzo] for about $50. Everything was fine with it, except for the failed bios update that rendered it useless to the last owner. [Janzo] set to work with an Arduino on a quest to repair the bios. He looked up the datasheet for the EEPROM that stores the bios and did some delicate soldering to gain access to the power and data pins on the device. A bit of trial and error and he was able to read the registers. Some comparisons between the output file and the official Eee PC bios file in a HEX editor confirmed that the first 80 bytes were fine but after that something went wrong. After coding a quick Python script [Janzo] reflashed the chip and had the computer up and running again.

We’ve seen Eee PC bios recovery before. This is a very simple method because it makes use of the simplicity we find in the Arduino. Nice job.

Update: Flash_Destroyer final destroys EEPROM

The Flash_Destroyer finally succeeded in rewriting that EEPROM until its demise. When we originally looked at the device it had already recorded 2.5 million successful rewrites. The first appearance of corrupt data occurred at 11,494,069 but that doesn’t tell the whole story. The chip kept working for another 200,000 rewrites before finally showing repeated data corruption.

We do find the writeup pretty interesting. There’s one thing that we can’t stop coming back to though. In the discussion of our original article [Tiago] pointed out that long-term data retention isn’t being tested here. If the abuse of that EEPROM had ended after say five million rewrites, would it have been able to hold the data long-term without corruption? Let us know what you think in the comments.

[Thanks Drone377]

Russian Roulette… for EEPROM

There’s a loaded gun but its got only one bullet. Spin the cylinder, point at head, and pull the trigger. The game’s not over until the bullet is used and a player is done. This game’s got a twist though, the cylinder has at least one million chambers.

The Flash_Destroyer is testing the limits of EEPROM rewrites. It fills that little eight-pin chip with data, then verifies what has written. When it finds and error the game is over. The chip is rated for one million rewrites but while we were writing this it was already well over two and quarter million. We usually prefer to be creators and not destroyers with our hacks but there’s something delightful about running this chip into the ground. See the startup of this device after the break and click through the link above to see a streaming feed of the progress.

Continue reading “Russian Roulette… for EEPROM”

2600 game jukebox

[Yuppicide] sent us a link to a photo album of an Atari 2600 modified to play ROMs stored inside. We did some digging around and have an idea of what’s going on. It seems that the creator, [Victor] has taken his Atari 2600 cartridge emulator one step further.

Previously, he had replaced the chip in an Atari cartridge with an EEPROM that he could reprogram via a ribbon cable. This new iteration places that EEPROM inside the case of the gaming console along with a PIC development board. The PIC board interfaces an SD card with somewhere around 1200 ROMs on it. Three switches added to the front of the Atari allow the user to cycle through available games and flash the desired title to the EEPROM. As you can see, a 2×16 LCD display now resides in the cartridge opening.

This seems a little more eloquent (and less legal) than the Super Genintari.