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𝔎𝔦𝔯𝔞 , 09-05-2026, 07:24 PM

there does not seem to be a circuit diagram for this type of connector so I have no idea how it should be connected or what kind of resistors or capacitors to support the connection

https://www.hirose.com/product/document?clcode=CL0609-0033-6-00&productname=DM3AT-SF-PEJ2M5&series=DM3&documenttype=Catalog&lang=en&documentid=D49662_en

can anyone help with this

, 09-05-2026, 07:33 PM

🤖 In the meantime, here’s a response from the [FEDEVEL AI HW Assistant]().
It helps to find relevant resources for your question, but it may make mistakes as it’s still in early development.

This is the response from the AI Assistant:
While the specific Hirose DM3 microSD connector isn't covered in the available resources, here's how to approach SD card interfaces generally based on similar component integration shown in the videos:

1. **Power Connections**:
- Use 3.3V power (SD card standard) with 100nF decoupling capacitor close to the connector's VCC pin
- Add bulk capacitance (1-10µF) near the connector for voltage stabilization
([Example power decoupling](https://www.youtube.com/watch?v=N4cLFE0FF2U&t=1325))

2. **Signal Lines** (CLK, CMD, DAT0-DAT3):
- Use series resistors (22-33Ω typical) near host side for impedance matching
- Add optional pull-up resistors (10-50kΩ) if your host controller doesn't provide internal ones
([Pull-up resistor example](https://www.youtube.com/watch?v=W0bmmF1wTEs&t=1418))

3. **Card Detection**:
- Use the connector's built-in switch pins (if available) with 10k pull-up to 3.3V
- Add debouncing capacitor (1-10nF) across switch contacts

4. **ESD Protection**:
- Place TVS diodes on data lines close to connector
- Use ESD-rated capacitors (10pF-100pF) for high-frequency filtering
([ESD protection example](https://www.youtube.com/watch?v=N4cLFE0FF2U&t=1918))

Key tips from the videos:
- Place optional 0Ω resistors in series for rework flexibility
([Optional components example](https://www.youtube.com/watch?v=2LWXKOEnIJE&t=175))
- Keep high-speed signals (CLK) as short as possible
- Use ground pour under the connector for shielding

While your specific connector's pinout isn't shown in the materials, the general SD card interface principles apply.

, 09-05-2026, 07:33 PM

Cross-reference with SD Association physical layer specifications for exact values.

You can continue chatting with the AI Assistant here:
https://fedevel.com/hw-assistant

⟨yukko|Ψ⟩ , 09-06-2026, 12:03 AM

i actually have wired this exact sd card holder

⟨yukko|Ψ⟩ , 09-06-2026, 12:03 AM

i wired mine to have spi communication

⟨yukko|Ψ⟩ , 09-06-2026, 12:05 AM

⟨yukko|Ψ⟩ , 09-06-2026, 12:06 AM

@𝔎𝔦𝔯𝔞 this schematic worked well for me

⟨yukko|Ψ⟩ , 09-06-2026, 12:06 AM

𝔎𝔦𝔯𝔞 , 09-06-2026, 05:48 AM

im wiring for SPI too, but how do you know where to put pull ups and what not

⟨yukko|Ψ⟩ , 09-06-2026, 07:04 AM

CS is active low, so it is pulled up. when the microcontroller wants to use CS, it actively drives it low

⟨yukko|Ψ⟩ , 09-06-2026, 07:04 AM

MISO MOSI and SCLK are okay as is I think

𝔎𝔦𝔯𝔞 , 09-06-2026, 09:28 AM

typically CS is substituted with the SDA or SCL pin of i2c right? that is what I did in a previous PCB design
I think the i2c and spi pins are pulled up by default in module boards already. I am using XIAO ESP32S3 module

𝔎𝔦𝔯𝔞 , 09-06-2026, 09:30 AM

for VCC, why did you use 1uF and not 100nF

𝔎𝔦𝔯𝔞 , 09-06-2026, 09:30 AM

or 22uF, thats what i used in a previous pcb for both 3v3 and 5v

Robert Feranec , 09-07-2026, 05:56 AM

We used DM3 in our iMX6Rex project, scroll down, there is also schematic: https://www.imx6rex.com/application/imx6-development-board

⟨yukko|Ψ⟩ , 09-07-2026, 11:32 AM

its somewhat arbitrary but oversizing is better than undersizing i think

⟨yukko|Ψ⟩ , 09-07-2026, 11:32 AM

100n should be fine

⟨yukko|Ψ⟩ , 09-07-2026, 11:32 AM

i just wanted to lower my BOM costs

⟨yukko|Ψ⟩ , 09-07-2026, 11:32 AM

not sure what you mean here as i2c is incompatible with SPI

⟨yukko|Ψ⟩ , 09-07-2026, 11:33 AM

you should check your microcontroller pinouts to see which pins have hardware spi. if those do not work then you can always bit bang the spi lines

𝔎𝔦𝔯𝔞 , 09-07-2026, 12:53 PM

there is no dedicated CS pin so I used one of the i2c pins to substitute it, but I recently realized I could have used any gpio for CS

𝔎𝔦𝔯𝔞 , 09-07-2026, 12:56 PM

looks like just one decoupling at power side

𝔎𝔦𝔯𝔞 , 09-07-2026, 12:56 PM

is that all for the filters and what not

𝔎𝔦𝔯𝔞 , 09-07-2026, 01:16 PM

i have another question the dm3 has A and B type, what is the difference which should I use does it matter at all?

⟨yukko|Ψ⟩ , 09-07-2026, 04:26 PM

i believe it depends on how many detection ports you want

⟨yukko|Ψ⟩ , 09-07-2026, 04:26 PM

but im not sure

𝔎𝔦𝔯𝔞 , 09-08-2026, 06:26 AM

𝔎𝔦𝔯𝔞 , 09-08-2026, 06:26 AM

this is a schematic i found for a radxa board

𝔎𝔦𝔯𝔞 , 09-08-2026, 06:26 AM

no idea why they called it TF card

𝔎𝔦𝔯𝔞 , 09-08-2026, 06:27 AM

they have TVS diodes for those other pins but the 3v3, why?

⟨yukko|Ψ⟩ , 09-08-2026, 09:48 AM

just ESD protection but i guess they may have forgotten it for the 3v3 pin

⟨yukko|Ψ⟩ , 09-08-2026, 09:48 AM

unless the sd card already has esd protection?

𝔎𝔦𝔯𝔞 , 09-08-2026, 11:15 AM

you can check here
https://dl.radxa.com/cubie/a7a/docs/hw/radxa_cubie_a7a_v1.10_schematic.pdf

QDrives , 09-08-2026, 03:06 PM

They have 4.7uF on the 3.3V -- capacitive divider.
A ESD spike of 15kV from 100pF (human body model) on 3.3V would raze the voltage with 0.48V to 3.78V.
No TVS diode can limit it that much.
However, that would also assume no inductance in the capacitor, which is also not the case.