Thanks Felix, I was hoping someone could clear that up. I'm not quite to that stage yet, but I'm reinvigorated to know that there's the possibility of help if I get stuck.
To explain a bit more about my project... I liked the idea of using ST chips for the IMU since they were cheap and had free samples available. ST had also been starting to hype their "iNemo" sensor fusion and AHRS platform. iNemo is supposed to run on STM32F103s, at least at first. That, combined with the fact that LISA uses a STM32 processor, got me thinking that a STM32 + ST accel/gyro/magnetometer combo was the way to go.
So I decided I better learn the STM32 and got a couple VL Discovery boards. When I got the Discoveries I was pretty impressed with the units, and thought I'd do well to explore the capabilities. What I found out was that the Discovery actually has both F100 and F103 processors. The F103 runs the "ST-Link", which is STs USB programming/debugging link. What's cool about the Discovery units is that there are two 4-pin headers on the board. If you jumper one side you use the st-link to program the onboard F100. If you remove the jumpers then the other 4-pin header allows you to use your discovery to connect to any other ST processor and flash/debug it.
After reading about a hack to program the F103 using another discovery unit, requiring soldering two wires to one side of two SMT solder bridges, I figured out how to tie the right pins together on the bottom so that you end up with one header to program the F100 and one header to program the F103. Now I could easily flash and debug either processor on the board. So now the Discovery becomes a nice little dual processor dev board with USB. Unfortunately, the F103 is not connected to very much, and what it is connected to is a little less than clear to me. The processors are connected together by at least two lines and the F103 is connected to a USB port. I also know that none of the I2C lines are connected and the F103 does not have a digital crossbar.
What I ended up doing for the moment was to pull up two I2C pins and solder little wires to them. I think I've come up with an easier and better method now that involves tacking some small wires to the processor, scratching out a couple existing traces, and tying those I2C lines to the existing header pins. It's somewhat tedious, but making a nice autopilot board for under $10 seems worth it to me.
Anyways, the master plan is to have the F103 tied to the IMU and running ST's iNemo sensor fusion / AHRS firmware. The F103 will be dedicated to the sensor fusion and processing the "true extended state Kalman filter" that ST is hyping. It will also do some USB tasks, communicate with the F100, and do whatever else it's limited connections will support (hopefully flashing the F100 and helping put settings into it from the USB).
So essentially I have the hardware side worked out and now I get to enjoy the real fun of beating my head against the wall trying to program the thing. But, I don't see any insurmountable problems standing in the way.
Right now my problem is that the code ST has released only compiles on IAR 5.x. I wrote and asked them for Atollic/eclipse support and they told me that only IAR is supported for now. I wrote them back and told them that IAR is NOT supported, only an old version of IAR that you can't get anymore is supported. IAR 6.2+ has some major CSMIS problems which seem to have no good workaround since ST doesn't seem to have any CSMIS files out that actually work with current versions of IAR.
So I need to figure out how to compile the code on some toolchain that I can actually get my hands on. I just don't know enough about these toolchains to figure it out at the moment. Seems like there's a lot of workspace/project file settings to configure, and I don't really know what I'm doing. The free version of Atollic doesn't have the graphical setup features of the pro version, so it seems like I have to do a lot of digging through XML files and the like to get things running.
At the moment I can flash the iNemo DFU firmware onto the F103 and the iNemo code also. The DFU firmware (USB firmware upgrade tool) works just fine. I can actually use the USB connection to flash whatever I want onto the F103. Of course, the iNemo code is written for their $250 IMU evaluation board and I need to change a few settings to work with my pinout, and strip away the rest of the code related to their other sensors.
My limited success with the iNemo code has kept me mucking about with it, but I'm about ready to try and get the PPZ code running on the F100 and worry about iNemo later, if I even really need it.
Is anyone else interested in working on this project with me? The potential benefit of the project is the development of an ultra-cheap PPZ hardware platform. It also will offload the effort of AHRS and sensor fusion to ST. Hopefully they can then do all the math and worry about supporting their chips.
ST is also now producing a cheap ($35) little IMU designed to plug into their sensor eval board (STEVAL-MKI108V2). It uses the latest L3GD20 and LSM303DLHC MEMS sensor chips. (L3GD20 is the replacement for the L3G4200D). The L3GD20 is claimed to be immune to audio frequency noise and vibrations.
STEVAL-MKI108V2
http://www.st.com/internet/evalboard/product/252687.jsp
So the end product of the project will be a PPZ hardware platform consisting of:
STM32VLDiscovery - $7 (new ST suggested retail price)
STEVAL-MKI108V2 9DOF IMU - $35
Fastrax UP501 GPS - $28
---------------------------------
= $70
I think a $70 hardware platform would be an amazing price breakthrough and really lower the barriers to participation in the PPZ project. Cost alone might draw new people to the project, but existing members with a significant investment might also consider the benefit of redundancy. People with existing systems could add a completely redundant backup to their system for a reasonable price, and new people could have a redundant system (excluding radio link) for only $140. That could be a great safety improvement.
I'm hooked on doing the project and if anyone else wants to help out it might not take me a year to get it working. I'm happy to modify the discovery boards for anyone who wants to get involved without bothersome soldering. Just shoot me an email. I'm planning to get more Discovery boards shortly and should have some modified ones ready to go before long.
The only real disadvantage I see to this project is that it will require a rather complicated main wiring harness to connect everything up since it's not a custom board. Fortunately, I think a IDE hard drive cable (or similar) will work pretty easily and we'll just have to put the right connectors to the right wires to end up with a decent connection system. I'll be happy to make those also as soon as it is figured out how the pins best map with the PPZ code.
-Jake
----- Original Message -----
From: Felix Ruess
Sent: 01/27/12 05:16 PM
To: address@hidden
Subject: Re: [Paparazzi-devel] Introduction, Q's about STM32 development
Hi Jake,
just a quick note: I don't think that creating new board files for the
STM32VLDiscovery board would be much work (if you already know
paparazzi). Also flash should just be enough, depending on what
subsystems/modules you include. Flash usage is roughly around 120kB on
my setup here..
Cheers, Felix
On Sat, Jan 21, 2012 at 4:15 PM, antoine drouin <address@hidden> wrote:
Hi Jake
The idea is that the door kicks open and the rope falls to the ground where it is drug a short distance where particles stick >to the collector, then the motor kicks in and winds the sample back up into the pod. Then the plane returns to base. > Using variations of that system should make it easy to snag lots of samples from remote locations for cheap. Obviously >the danger is that the sample rope gets tangled and the plane gets dashed into the ground at 30+ mph.
how far do you need to go fetch your samples? Have you though about
doing it with a quadrotor?
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