Burns,
I think I have addressed all the issues you raised except pull-ups on SPI. If we don’t need them I can easily remove them from the boards.
I will order some 91 nH inductors and a few more values near by and replace the zero ohm resistors. The zero ohm resistors have some inductance by the way. I can measure this with limited accuracy using an inductive bridge I have. I
think dynamic testing is needed to prove out best value. May ask Jim to help with that later.
I thought you uploaded your code changes to a fork. Can you tell me how to find that? I just looked around and it is not obvious to me.
Would you also speak to what you feel got the serial port working? I assume there is a new HCG file in your code I would like to review that.
I have another conference call this afternoon with SARA that will go till 3 or so.
I would like to test the MRAM on one of the other boards. These chips have not been removed and resoldered.
I want to buy four new memory chips and have the assembly house place them on the board you have.
May put a loop in the code to test each chip and flash leds with results. Then they could perform a test after soldering.
I plane to make all the changes I know about and assemble the boards I have. Hope to get this done and ship all of them out by the end of this week.
Will have done limited testing to RF but that can catchup later.
Bob
I've found a few minor design issues which I don't think will affect us in the short run, but may not be what we want:
1) I already told you (Bob) about the addresses for the Max temp sensors. As set, they collide with two of the possible 4 addresses on an ADS7828, a commonly-used and space-tested A/D converter
that some satellite might use. We talked about this before and it should all be straightened out.
Yes, Let me add this to the schematic with the new address values to be used on next board build if any.
2) I just noticed that PWR_SW_AX5043 and PWR_SW_SSPA are connected to AD1IN_8 and AD1IN_5, pins 78 and 83. They are used as input to the MAX4995SAL power switch/limiter. While you could use these
AD1IN pins as an input GPIO (read the voltage and subject it to a threshold for high or low), I don't think it is possible to use these for output. AD1EVT might be usable for output but I'm not sure what effect it would have on the bult-in a/d converter.
I suppose you could use the nearby MIBSPI5 pins. They appear to be usable as GPIO pins and are physically near the ADC pins.
Will have to move these lines over as you indicated. Will do that with jumpers.
I think the current way it is will work for the moment, since if I read the datasheet right, the "ON" pin or the MAX4995AL really should be ON_N. That is, a low value on it turns the power on,
and you have a pulldown there. So I think the 5043 and the SSPA will always be on since the ADC inputs should be high impedance.
3) This may just be a doc issue. I think that "PWR_FLAG" on the schematic can't be a circuit, right? OTherwise you'd have lots of weird stuff connected together. If they are actually test points,
I think they should be labelled as such (TP1, TP2, etc) and marked in silk screen on the board.
This is no problem, an artifact of KiCAD and needed to just to indicate this is a power connection so DRC handles it properly.
4) And finally, from what I have read (and seen on other projects), I don't think the SPI busses need pullup resistors EXCEPT for MISO, and that one should be VERY weak. (One of our devices does
not use MISO very often but it appears not to be able to pull much current, thus requiring the really weak pullup. But as I recall a builtin pullup either was not enough, or it could not be used when the pin was used as an SPI device). I can put a scope
on the MISO line for the AX5043 to see if it is getting pulled down enough with the 10K. Likewise, I'll see what the other pins look like when connected to the push/pull output of the SPI master.
We will add a a pull up resistor for next build. Try to use internal pull up now and if this want cut it we can add a pull-up to these boards.
Don't take these critiques as anything other than helpful. I'm no expert here...I just found these things in the process of trying to debug the software, and in a couple cases from tracking down
some really PITA problems on Fox and/or Golf!
No problem, you are the first person that has looked at things closely and when you start solving issues you are forced to do so. We all make mistakes I have have made plenty. Thanks.