insideGadgets

I was given the chance by the kind folks at Element14 to select a part from their website and do a review on it. I chose the Olimexino STM32 board as it’s the next step up from the Arduino and can act similar to an Arduino. The Olimexino STM32 uses an ARM microprocessor running at 72MHz which is 4.5 times faster than the Arduino’s 16MHz. You can find the Olimexino range of products at http://au.element14.com/olimex/.

It has the following key features packed into the one board, to see more of the features click here.
- Allows 9V to 30V input
- microSD card capability
- Ability to use and recharge a Li-Ion battery
- ARM 32-bit processor with 128K flash, 20K SRAM, 12-bit ADC, 16-bit PWM, 39 I/O pins, SPI, i2C, CAN, RTC, etc
Note: The ARM micro doesn’t feature an EEPROM like AVR micros do.

As the Olimexino STM32 is based on Maple (or seems to be) we can use the Maple’s IDE (which is a re-brand of the Arduino’s IDE) to start writing and uploading code with ease, most Arduino functions have been ported to the IDE. We have the blinking LED sketch shown below.

(more…)

Read Full Post »

In my Adding EEPROM to the SATL post I briefly spoke about my multimeter not being about to measure the current of the SATL when it was writing to the EEPROM, mostly due to the fact that it happens so quickly in under 50ms. I decided that solving this problem would be my next project to work on.

My thoughts are to have an MCU sampling the ADC, use a resistor’s voltage drop to calculate the current then write the result to SRAM (instead of an EEPROM as it would take 10ms for each write). If possible, I would like it to also be powered by a 3V battery.

The maximum ADC samples per second that the ATtiny85 can do is 15,384 (15KSPS) at 200KHz which when compared to chips designed specifically for ADC that run at 200KSPS doesn’t seem like a lot, but in our case it’s a lot. The reason is that if we had a 64Kbit SRAM, it would only be able to store 8,192 samples which is just over half of the 15K samples per second, it would only record 0.5 seconds before running out of space. For a 256Kbit SRAM it would be 2 seconds.

Design attempt 1

Naturally I start up a circuit simulator and play around with different value resistors, resistors to simulate the load and find the voltage drops. Eventually I came up with a design that should be able to measure 10uA to 10mA using 3 resistors, 3 mosfets (for switching each resistor on/off) and use 2 ADCs.

(more…)

Read Full Post »

I thought I’d do a quick teardown on a generic 4GB USB thumbdrive that stopped working, I was given this drive to be destroyed.

When inserting the thumbdrive it would recognise it however it would ask to insert a disk when clicking on the volume, so let’s open it up.

It was very easy to open up and upon first glance the build quality doesn’t seem too great but then again it’s a generic USB drive. We can see that it seems PCB wasn’t exactly made for the case which is why they have the glue to hold it in place.

(more…)

Read Full Post »

I received a comment by Steve asking if I was going to combine the SATL and SAVL together. It sounded like a good idea to me so I’ve gone ahead and done just that.

The schematic was updated with the voltage sensing circuit,  I added in a Mosfet so that we only draw power from the voltage source when needed and you’ll notice there are 2 jumpers – Temp and Volt. You can switch between logging temperature and voltage by completing the connection of the jumper and modifying a variable with button presses.

(more…)

Read Full Post »

As discussed last week the Standalone Temperature Logger has now been updated to v3.0.

The PCB works well, with a few more parts needing top layer soldering it was a bit trickier.

The improvements made were:

• Added external I2C EEPROM support with automatic EEPROM size checking
• Updated 10K resistor divider to 1% tolerance
• Added 28 seconds to delay options available
• Updated temperature resolution to be 0.65C which is rounded up or down in 0.5 – 1C increments thanks to the suggestion made by tytower

Download SATL_v3.0 or view the updated Standalone Temperature Logger project page.

Increasing the resolution of data saved to EEPROM

A user named tytower left me a comment about increasing the resolution range that the SATL uses when saving to the EEPROM from my value 90 to 255 to use 1 to 255 which has prompted me to include his suggestions in the SATL v3.0. Tytower explained that the temperature range is -40C to 125 which is 165 data points and if we take the maximum value of data stored in the EEPROM 255 (minus 1 for the value 0 being our stop bit) and divide by 165, we get 1.545 which means we can increase our resolution by 1.5x. If we divide 165 by 255, our new resolution is 0.65C degrees (before I just had it as 1C) and to keep things nice I’ll round up or down to 0 or 0.5.

(more…)

Read Full Post »