Raspberry Pi meets Invensense MP9150 (Thesis)

I've been playing with the Raspberry Pi for a couple of months now, and I must say it's a wonderfull piece of equipment. The ARM processor is very powerfull, and Debian is a great OS. I've been using gcc to compile my pprograms, which I have some experiemce in. The first stock Debian image didn't have I2C support, and it was quite a chore to compile the kernel. With the new Raspbian distro, I2C should be included, aswell as hardware FPU support. I've not started using it, but probably will soon.

I've managed to port my DCM code to gcc, and it's running well. I'm no longer using my sensor stack, but a development board for the new Invensense MP9150. That chip is basically an MP6150 gyro and accelerometer combo with a magnetometer on the side. I've not started using the magnetometer, but will soon. I'm currently working on a roll/pitch platform that can simulate motion. Will post more about that very soon...

LM75 based I2C temperatur sensor PCB

Again Zuken Cadstar has messed up my PCB! I'm sure there must be something I'm doing wrong, but for some reason, the ground plane copper fill that cadstar does ends up separating the plane in parts.

Anyway, apart from finally soldering together a functional board, I was eager to test it out together with my newly aquired buspirate. Not much success thought, but I think I know why: it's a problem with the address lines on the LM75; it's either a too low resistor value between the address lines and the dip switch, or the address selection through a dip switch is not a good idea.

Hardware Platform : The RaspberryPI (Thesis)

I started off looking for a hardware platform that would suit my particular needs, of which there weren't many, but from out of nowhere came the RaspberryPI. Before that I had considered several differen microcontrollers, homing in on a 32-bit microcontroller from either Atmel or Microchip. But that has all changed! I've pre-ordered my first board, and it doesn't look like this is just another piece of Vaporware: The organisation behind the board has teamed up with both RS and Farnell.

The Raspberry fulfill several criteria as a hardware platform for my thesis:
- Powerfull CPU
- Hardware FPU
- I2C
- Other low-level stuff, like GPIO, SPI, etc...
- Low(ish) power: 200-300 mA
- Small
- Cheap: 25 USD or 35 USD
- Several USARTs
- Ethernet
- Linux based (stable, secure, advanced, etc...)
- Choice of compilers: Python, C/C++, Ruby, + many more.

Can't wait to get mine. Shame my order was pushed back several weeks :(

A small PCB project, LM1307 Digital temperature sensor - Part 2

It's been a while since I've done had time for anything but my new job and my new house, hopefully I'm over the hill now, and back in bidniz.

So, not much of an update, but I've soldered the LM1307 sensor and the DIP switch onto the PCB. As I've mentioned, I'm only using 1206 discrete components, none of which have made it onto the board just yet.



I'm settling into my new workshop in my new house. It's rather messy at the moment, and I can't find anything. It's a little cold in there too, but it's brighter, bigger, and has much potential.

A small PCB project, LM1307 Digital temperature sensor

This PCB has high reuse value, I have a few projects in mind already: aquarium regulation, CCD cooling, grow house control, among a few.

I decided to use only 1206 components, as they are infinitely easier to hand solder. A smd dip switch selects functions and IO addresses.

The LM1307 also has a digital output, which I connected up to a NPN transistor, so it can drive a small load (up to a few hunded mA).

The board is quite small, and even with four 3.5mm mounting holes and rounded corners, it still measures less than 3x3 cm.

Sensor stack (Thesis)

It's been a while since my last post, not that there hasn't been progress: I've got ahold of the right spacers, so the sensor stack looks neat and ready to be mounted (see photo). Unfortunately I still have to use STK600 to do USART line conertions, because I ordered the wrong footprint regulators (sot89 instead of sot223). I'll soon have that sorted thought.

There is still more work to be done with the ARS algorithm before I can test it against a real system, but I'm confident that I'll have something in time for the test.

I still haven't decided on which CPU to use, but I'm leaning towards a uC.

Power & IO PCB for Attitude System (Thesis)

Over the last couple of days I did another module for the attitude system stack. The last one I did was the uC PCB, which won't be used in the final system, due to its low processing power. This  new power and IO will be part of the final system, as it will take care of the external power and interface convertion.

First of all, the PCB takes power and regulates the voltage down to 1.8V, 3.3V, and 5V for all the sensors and uC/FPGA. I was a little unsure of wether I should put in a bridge rectifier on the power input, to make sure the polarity would always be correct. In the end I skipped it. Secondly the PCB has a USART signal converter for external I/O, together with a 9 pin DSUB-F connector. This  is my primary interface.

I also put on a RJ45 socket, in case I also implement an  ethernet interface, but with just a simple 2x4 header.

Finally I have to commend the guys at iTead Studio for their excellent service. I was very pleased with the last batch of PCBs they made for me, at a price you just can't beat. But this time they kindly pointed out to me that I was missing two drill holes for the RJ45 socket (see picture). That is just awesome! Thank you!! The error was due to the way STARCAD was set up not to include non plated drill holes in the drill file. Quickly fixed, and updated files sent away. Now for the waiting part ;-)