Is SD card functionality supported?

[idea--list]

I am considering this platform for my next project.
Just wonder if SD card functionality is already supported or will that be in the close future?

[oclyke]

Hi @idea--list,

SD functionality is definitely possible, however it is not yet implemented. There will be a few possibilities to do so:

1. Use a HW interface -- Apollo3 has a 'secure card' interface built-in however I am not familiar with what that is. Does it relate to 'secure digital?' If so we may develop SW support
2. If there is no HW support for SD then we can easily implement the SPI version of SD interface using the IOMaster functionality
3. Finally at the highest level of abstraction we may also use SD SW support that relies on the Arduino "SPI.h" interface. This option may be possible to get working in the shortest amount of time because the fundamentals of "SPI.h" are already imemented.

Thanks for asking!

[nseidle]

What a wonderful handle idea--list!

SD is supported via SPI and the Arduino standard SD libs (Bill Greiman's last time I checked). But please keep the ideas coming. Doing an encrypted flash example is a fascinating idea that I'd like to see.

[oclyke]

@idea--list
Here's some more information:
https://forum.sparkfun.com/viewtopic.php?f=164&t=50250

Most important to note is that there is currently a bug in the SPI library. We will fix it soon but have other priorities first. In the meantime you can manually fix "SPI.transfer(byte)" by adding a return statement "return 0;" to the end of the function. Somehow this was not caught by the compiler.

[idea--list]

My project is currently based on the MAX32630FTHR board that also has an SD-card slot.
I am logging data at about 500Hz sampling rate that yields up to 100MB data per day.
Turns out that board has an SPI implementation that impacts the transfer rate quite much (~70 KB/sec), thus data transfer takes hours if i connect that board to my PC (USBMSD).

However if i remove the card from the board and put it directly in the pc, i can copy the same amount of data in just some seconds... This is a huge bottleneck in real IoT as we either have ease of use (card does not need to be removed from the IoT device) or great transfer speed but that needs a different HW design as the sd card needs to be removed to copy the data

So i wish you will end up with an SD (and not SPI) implementation ;-)

@oclyke Did some research the datasheet of the Apollo3 MCU mentions "Secure Card IO" on page 405, so the chip supports SD-mode that is much faster then via SPI.
Also found the specification of the SDIO-mode that can be downloaded here: https://www.sdcard.org/downloads/pls/pdf/index.php?p=PartE1_SDIO_Simplified_Specification_Ver3.00.jpg&f=PartE1_SDIO_Simplified_Specification_Ver3.00.pdf&e=EN_SSE1

[oclyke]

@idea--list,

An SD mode would be really cool but I don't think that the Apollo3 has SD support. I was originally hopeful about the 'Secure Card' features but I do not think it is related to SD. (See ISO 7816 info below). I just finished some pressing bootloader development and so I will shortly get to testing the SD library. I'll keep you updated about it.

https://en.wikipedia.org/wiki/ISO/IEC_7816

[idea--list]

@oclyke
Thanks for the info. Well even SPI is better than nothing. However Ambiq explicitly mentions "Secure Card IO" in their datasheet. That is how most manufacturers make clear that their product supports the original SD-mode with its benefits over just a plain SPI. I hope also Ambiq knows this difference and they are not using exactly those words just by mistake.

Turns out that for SPI implementation you need 1 pin less on the card slot than for 1-pin SD-mode (and there is also a 4-pin version of SD-mode that is the fastest). This means you just can not take any sd card slot until you are not absolutely sure what does the MCU support. Otherwise you might choose just a card slot that only supports SPI and later realize that the MCU would have support for SD-mode as well. But by then you already have a ready made HW design and some thousand units... :-)
Maybe best idea would be to contact Ambiq from your behalf to clear if SD-mode is an option with this MCU or only SDI-mode is supported.

Meantime i also found opensource code for the SD-mode implementation, let me know if that would help you in any way.

Luckily enough these boards are still in the Spark X phase and if i understood right, you plan release RedBoard series board(s) after the certification. Meaning you can still easily alter HW design if it unlocks much higher speeds.

[oclyke]

@idea--list totally! We are definitely open to improvements. I am genuinely confused about the "Secure Card IO" stuff in the Apollo3 datasheet. I will try to get a more clear idea from Ambiq.

The good news is that whatever Secure Card is the Artemis module should be able to use that peripheral. The only Apollo3 pads not broken out on Artemis are 30 and 46. (Pad 47 has special requirements on start up b/c it is a strapping pin, but it can be used) Pad 46 has SCCRST as a functionality, but that functionality is also exposed on pads 26 and 16. The others (SCCIO and SCCCLK are available on several pads as well.

I would definitely be interested in the open source SD interface. Is that a bit-banging implementation? If so we could probably make it pretty fast with the Apollo3 fast GPIO features. Please share the link!

[idea--list]

@oclyke
Here a discussion on Github: ARMmbed/mbed-os#6384
And the code: https://github.com/JojoS62/mbed-os/tree/add-component-sdio-blockdevice/components/storage/blockdevice/COMPONENT_SDIO

The code is well commented, made for mbed-os which is a C++ based platform. Hope it gives some inspiration how to implement it your way. I mean in case the Apollo MCU has native SDIO support.

[oclyke]

@idea--list

We just released v1.0.6 (available through Arduino board manager) which allows the Arduino SD examples to work out of the box. Please give it a try and let us know if there are any more issues!

Thanks for taking the time to help us improve the Apollo3 core.

[justiceamoh]

Hi @oclyke, I'm having issues trying to interface with microSD using the Artemis Nano. I am using the Sparkfun microSD breakout board.

I've read in this issue and on the Sparkfun forum post that SD support is now built-in but the Arduino SD examples don't work for me. With a logic analyzer, I see communications on the SCK, MOSI and occasionally on the MISO pins. But the Arduino examples all fail to initialize the SD. It won't get pass the lines:

  while(!SD.begin(9)) {
    Serial.println("initialization failed!");
    delay(100);
  }

For hookup, I have:

microSD	Artemis Nano
SCK	SCK (Pin 11)
DI	MOSI (Pin 12)
DO	MISO (Pin 13)
CS	Pin 9
VCC	3V3
GND	GND

I am inferring from forum posts that CS/SS is not necessary with the Apollo3, right? Is there something I'm missing?

[nseidle]

Works for me: RedBoard ATP + microSD + SparkFun X 1GB card. I used the built-in SD CardInfo sketch.

The CS is needed to make SD work with SPI.

I'll see if I can replicate on a Nano...

[nseidle]

Works fine for me on Nano with CS on pin 9. I was originally worried that pin 9 was also used as TX1. Serial1 is configured at power up and TX/RX are set as UART. But when card.init(SPI_HALF_SPEED, chipSelect) is called I believe it re-inits the TX pin as GPIO 9.

You should be good. Let me know if you're still having issues. Consider opening a new issue so we can keep the threads clean.

[justiceamoh]

Thanks @nseidle ! I got it working with another SD holder from an old board -- and you're right, CS is required. I probably damaged the microSD breakout board. Thanks for your help and the rapid response!

[nseidle]

NP! Sorry to hear the breakout board was an issue. Feel free to pin our tech support group and get a replacement if needed.