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  1. The data sheet for the MS5611 shows separate pins...

    The data sheet for the MS5611 shows separate pins for protocol select and SPI chip select.
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    I know nothing about that library code. I have...

    I know nothing about that library code. I have only used character LCDs with the MSP430 and writing my own code. Various versions over the years: 4 bit, 8 bit, and with or without read.

    Before...
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    The resistor is there to limit fault currents...

    The resistor is there to limit fault currents when the clamp diode turns on. (5V signal to 3.3V device) Most devices list a current limit (a few mA) in their data sheet but I couldn't find one here....
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    ACMD41 is not the first command sent (CMD0 and...

    ACMD41 is not the first command sent (CMD0 and CMD8 precede it) and it appears that this error code is sent if there is a timeout waiting for a response. I can't think of any reason why a card...
  5. Part of that schematic fragment bugs me. While...

    Part of that schematic fragment bugs me.

    While it isn't shown as being connected to anything else, the INA169 output is connected to a capacitor rather than the required resistor. The INA169 puts...
  6. It has been a while since I have looked in this...

    It has been a while since I have looked in this particular rabbit hole, so I have forgotten most of what I learned. :-)

    Pretty much everything I learned, I learned here:...
  7. That is not an ESD clamp. It is simply there to...

    That is not an ESD clamp. It is simply there to protect against voltages which would trigger the internal parasitic SCR between Vdd and Vss. You still have to limit current through the clamping...
  8. Unused GPIOs should be set as outputs or at the...

    Unused GPIOs should be set as outputs or at the very least have their internal pull ups enabled so that they don't float. While the pins on CMOS devices will usually have clamping diodes on them...
  9. Connecting any input pin directly to something...

    Connecting any input pin directly to something which the user can touch is a bad idea. Of course I just finished reading Henry Ott's book from start to finish so that final chapter on ESD may color...
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    Microchip makes some nice FET drivers in several...

    Microchip makes some nice FET drivers in several varieties. Something like the MIC4416 should do the job.
  11. It appears that all of the ranges are multiples...

    It appears that all of the ranges are multiples of 30. So divide EncoderCount by 30 and use the result to index into a table.

    digitalWrite(30, encodertable[EncoderCount/30]);
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    Which suggests that there is something flaky with...

    Which suggests that there is something flaky with the pot. Since you are feeding the pot from an external supply, drop its voltage to say 2V. Does the problem occur at a proportionally lower voltage?...
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    The time required to hold CNVH high is 10ns. It...

    The time required to hold CNVH high is 10ns. It would require an exceptionally fast micro to violate that. I would worry with a Teensy 4.1 but not with a 3.2. The conversion time of 700ns is a...
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    I have a can of the MG Chemical Silicone...

    I have a can of the MG Chemical Silicone Conformal Coating that I use on boards that will be exposed to corrosive environments.
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    Wait a minute, are you really expecting to get...

    Wait a minute, are you really expecting to get 1.8V out of a LM317 with 3.3V in? The minimum input to output differential is 3V.
  16. Thread: GPS and DMA

    by UhClem
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    DMA works best with things that provide data in...

    DMA works best with things that provide data in nice known block sizes.

    You have what is effectively a continuous stream, since the GPS is not going to wait after each 4KB, you must always be...
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    If this is your first experience with RS485 I...

    If this is your first experience with RS485 I recommend digging up an old CIrcuit Cellar article titled "The Art and Science of RS485". Google usually turns up a pdf.

    One thing to watch out for is...
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    It depends a lot on your application. I went the...

    It depends a lot on your application. I went the low level route with no file system because I needed higher write speeds.

    When writing data to an SD card you get best performance when writing in...
  19. A MPU6050 should always report 0x68. Since this...

    A MPU6050 should always report 0x68. Since this is derived from the I2C address, it should also require a change to that to get something different.

    Unless it is not a MPU6050. Some other flavor...
  20. One of the things the startup code does is read...

    One of the things the startup code does is read the WHO_AM_I register to make sure that the magic number returned is as expected. Perhaps your board is returning a different number.
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    Since the SPI clock during initialization is...

    Since the SPI clock during initialization is supposed to be under 400KHz, a slow interface isn't going to be a problem at that stage.
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    I didn't have any trouble. Figure 35 shows a...

    I didn't have any trouble. Figure 35 shows a simplified version of the input circuitry including CADIN which is the sampling capacitor with a typical value of 1.5pF. Figure 36 shows the minimum...
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    You are sampling at 50KHz so have some sort of...

    You are sampling at 50KHz so have some sort of filter with a corner frequency of less than 25KHz. The average setting causes the ADC to perform 4 conversions just as fast as it can. The samples are...
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    This is of dubious utility. Sampling a signal...

    This is of dubious utility.

    Sampling a signal four times in quick succession might help if it were the ADC that was the problem. If you have a proper pre-sample filter in place then the only...
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    Empty as in nothing driving the input at all? Of...

    Empty as in nothing driving the input at all? Of course that will be noisy.
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    A charge amplifier is the usual thing to use with...

    A charge amplifier is the usual thing to use with a piezo sensor.
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    I learned a long time ago that electrons are...

    I learned a long time ago that electrons are notional little things that will go where they want to rather than where I think they should go. Details matter and schematics rarely show enough of it....
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    That current is required to meet all...

    That current is required to meet all specifications for that very high speed part. What is really required for your low speed application? And high impedance load? See Fig. 6 which plots output...
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    A couple of questions: Does the optocoupler...

    A couple of questions:

    Does the optocoupler really require 10mA?

    Do you really need optical isolation? (This implies that the receiver doesn't work well with others.)
  30. If you have 100 Ohm termination resistors on each...

    If you have 100 Ohm termination resistors on each end of the cable, then driving 5V into that will require 100mA. Compared to that, everything else is small change.

    The driver will not actually...
  31. Current demand on a RS485 net is usually driven...

    Current demand on a RS485 net is usually driven by the termination resistors. The transceivers don't require enough to matter much.
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    I am a bit concerned with the lack of a delay...

    I am a bit concerned with the lack of a delay from requesting data to reading it. The data sheet is a bit opaque on the conversion time. To sidestep that I would reverse the order of operations in...
  33. No. The charge on a capacitor is C*V. When the...

    No. The charge on a capacitor is C*V. When the ADC samples the signal it connects the analog input to the sampling capacitor.Typical a few pF. (See data sheet for the particular value for your...
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    Looking at the startup code, I see that the code...

    Looking at the startup code, I see that the code hooked into the early_hook by default disables the device watchdog. So any replacement is going to have to do that in addition to whatever else you...
  35. 1) Disabling interrupts in addByteToTx() just...

    1) Disabling interrupts in addByteToTx() just wastes time since txB_wptr isn't modified anywhere else. Certainly not in another ISR.

    2) The more natural (and faster!) way to write that is:

    ...
  36. Since analogReadContinuous is just a fancy way to...

    Since analogReadContinuous is just a fancy way to read the ADC result register, it can't be the cause of your trouble. The ADC will keep on performing conversions in continuous mode until you stop it...
  37. Pretty much every I/O module has clock control...

    Pretty much every I/O module has clock control that must be enabled before using that module. Those bits are in the SIM_SCGCx registers. The DAC also has to be initialized with things like your...
  38. Why in the world would you serialize the data? I...

    Why in the world would you serialize the data? I could see doing it if you were short on I/O but you aren't. Even at 75MSPS that fast processor is going to be hard pressed to read and do something...
  39. Including the conversion time is a wasted effort....

    Including the conversion time is a wasted effort. The ADC requires a clock input with very low jitter which means that you know (or should know) the timing precisely. Use that clock to trigger the...
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    That 8 Ohm load on your output can't be making...

    That 8 Ohm load on your output can't be making that opamp happy.

    If all you want to do is reduce the amplitude to drive a low level input then all you need are some resistors. But make sure that...
  41. Since you only need to sink current a simple NPN...

    Since you only need to sink current a simple NPN transistor driver is sufficient and robust enough so that the Zener isn't required.
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    You didn't fix it. The only way that can have any...

    You didn't fix it. The only way that can have any hope of working is if there is a connection between the opamp ground and the ground of whatever is driving J1. Which defeats the purpose of the...
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    I am wondering how that circuit is supposed to...

    I am wondering how that circuit is supposed to work.

    The the opamp has no explicit reference for the signal it gets from J1 (MIDI-in). It might be getting it via its output which manages to have...
  44. When I look for a data sheet on the AD8225 IA,...

    When I look for a data sheet on the AD8225 IA, what I find looks nothing like your schematic. The AD8225 is a single device in an 8 pin package with fixed gain and no Rg.

    What are you really using?
  45. 220nF seems a bit small for 30Hz.

    220nF seems a bit small for 30Hz.
  46. Do you have a plot of ADC counts versus input...

    Do you have a plot of ADC counts versus input voltage? Patterns in that might suggest where the problem lies.
  47. The more typical way of doing this would be to...

    The more typical way of doing this would be to use a timer in capture mode. That way it does the pulse counting for you.
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    I used a Teensy to build a rocket data logger...

    I used a Teensy to build a rocket data logger.
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    It depends on the environment. If you are putting...

    It depends on the environment. If you are putting SD cards into the socket only at a nice safe ESD protected workbench, then no. If you are going to let any idiot do it anywhere, then yes, you need...
  50. Another possibility. If you aren't using the...

    Another possibility. If you aren't using the Arduino environment, what are you doing for startup code? The C startup can spend a fair amount of time copying data for initialized global variables and...
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