Puma board building diary

[nitrousnrg]

I've been struggling with the mcu booting for a couple of days, and by asking Fred many things I fixed the issue.

The cpu wasn't exiting the serial monitor, freeems could only start after a soft SM reset. It turns out that the mcu was starting too soon and some things weren't initialized properly.

The TA card schematic has an mc34164 to keep it under a reset status until VCC reaches an acceptable level. Spin 2 should have something like that. My hack to get it working was adding a 2.2uF capacitor between the reset pin and ground.


Future tests to do (for others, not me):
* Try different values for the little RC delay. Smaller capacitance can aviod the use of a big electrolitic capacitor, but bigger resistance could lead to a too weak pullup.

Now I've freeems talking to mtx...

[Fred]

The TA card schematic has an mc34164 to keep it under a reset status until VCC reaches an acceptable level. Spin 2 should have something like that. My hack to get it working was adding a 2.2uF capacitor between the reset pin and ground.

As discussed by IM, the TA cards do NOT have this, it is only in the schematic. I've never had any issues with resets or coming out of reset strangely on my devices so I disagre with adding this extra component if the simpler case will work, as you've proven that it does. I'm certain the values of your hack can be made more workable and reasonable. If you want me to check component placement/values on the TA, let me know, whatever is on it works great. Nothing big/crazy, either.

Fred.

[nitrousnrg]

The crank sensor circuit (MAX9924) is working:
http://www.youtube.com/watch?v=mQd5VMvBqQY

I didn't try very high revs, I know the tiny resistors (R215, R216) could blow away. For the record: I didn't notice any unhealthy temperature in those resistors, although I can't touch the gas pedal and the board at the same time.

[Fred]

Marcos, why can't you reach the throttle to actuate it manually from the engine bay? Don't tell me that it'd drive by wire :-/ if so, yuck.

As for the resistors, we can surface mount some 1/2 watt units in 1/4 packages by hand if required.

Fred.

[nitrousnrg]

Don't tell me that it'd drive by wire :-/ if so, yuck.

Yuck

As for the resistors, we can surface mount some 1/2 watt units in 1/4 packages by hand if required.

You could put them in series, somewhere between the sensor and the chip.

[jharvey]

I know your are likely spending every waking moment with testing the circuits, working on ECUmanager and doing things that are of real importance. But I'm eager and anxious. What's going on?

You got firmware installed, and you got a signal from the RPM MAX9924, is that making it's way into a log file in ECU manager? Does it update a PC based RPM gauge? Are you going to stack two 1/4 watt resistors to make it a near equiv of a 1/2 watt? Ect.

Is there anything I can do to help? Perhaps I can look for a 1/2 watt resistor, ect. I know I shouldn't bug you because it will probably only take away from your dev time, but I'm eager to hear what's going on. It's exciting.

[nitrousnrg]

You got firmware installed, and you got a signal from the RPM MAX9924, is that making it's way into a log file in ECU manager? Does it update a PC based RPM gauge? Are you going to stack two 1/4 watt resistors to make it a near equiv of a 1/2 watt? Ect.

I'd replace the 10k by a smaller value and add in series some bigger trough hole resistors. The eval board has two 1206 per input, and with two 0805 I could end low in power dissipation.
Anyway, the loaded firmware (missing teeth) isn't able to perform RPM calcs, so nothing appeared in ecumngr. Also, I populated the secondary RPM input first, just in case I make an iron-sized hole in the board while trying to solder the little IC.

However, I did other tests with the analog circuits:
Battery voltage, MAT, and MAP are being measured ok, I saw the values changing in megatunix and ecumanager (actually, I don't remeber seeing MAT in ecumanager, but worked for sure in mtx). Oh, and no filtering at all. I didn't put any capacitor (I don't have those values!) so no noise questions please.

The values make sense (I heat the sensor and the bar goes up), but I imagine there should be some tables to translate ADC counts -> °C. The same for the MAP sensor. I must RTFM.

Years ago I ran my car with only IAT, MAP and RPM, so next hw test should be injector drivers, but I need some RPM reading. I'm getting familiar with the firmware, maybe I could get some reasonable RPM measurement by adding some code.

Btw, I'm not doing any deep testing or analysis, I'm just proving that all the important circuits are working.

Is there anything I can do to help?

There is quite a big thing, PM'ing you...

[Fred]

The values make sense (I heat the sensor and the bar goes up), but I imagine there should be some tables to translate ADC counts -> °C. The same for the MAP sensor. I must RTFM.

structs.h comments give you most stuff. Temp units are /100 to get deg K and then subtract 272.15 to get deg C. the first 32 16 bit vars are in internal units, the last 16 are raw ADC readings (for verifying math/logic)

Years ago I ran my car with only IAT, MAP and RPM, so next hw test should be injector drivers, but I need some RPM reading. I'm getting familiar with the firmware, maybe I could get some reasonable RPM measurement by adding some code.

Yep, feel free, keep me in the loop though, in case I need to change more stuff than just inside the missing teeth file. I want clean commits :-)

Fred.

[jharvey]

Any updates on how this is going? Have you received the digikey parts yet? Any new circuits tested out? Just a curiosity ping.

[Fred]

+1 too mucho tiempo en la playa = no bueno ;-)