Board design - MicroSD pins
- Thread starter Fyod
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Today's SD cards have 4 data pins: DAT0-3.
D0 is is used in the low-speed mode that many embedded processors use - say, 25Mps. Adequate for the need.
A real SDIO interface uses all 4 data lines streaming simultaneously. Many mid-range ARM Cortex M4 and up support 4 bit SDIO. It's how USB and SD get much higher speeds.
The M4 I'm using supports SDIO 4 bit with DMA.
SD card near processor should be OK unless you do things that make the MCU's package quite warm. Very warm. Unlikely without overclocking while computing the meaning of life.
Great explanation, thank you.
Heat came to mind so I made a mask-stop on the bottom layer (that'll be touching the processor) the size of the processor as a pseudo heat sink.
1] the copper and board will in theory draw some heat away
2] the heat conductive double-sided tape will help keep the SD board firmly in place without using unneeded pins
Heat came to mind so I made a mask-stop on the bottom layer (that'll be touching the processor) the size of the processor as a pseudo heat sink.
1] the copper and board will in theory draw some heat away
2] the heat conductive double-sided tape will help keep the SD board firmly in place without using unneeded pins
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PaulStoffregen
Well-known member
Heat from Teensy won't be an issue for the SD card, unless you do something crazy like encase the whole thing in tightly packed styroform. It just doesn't heat up that much, especially if there's any access to free air for normal convection cooling.
PaulStoffregen
Well-known member
Oh, looks really nice! Will these be sold somewhere?
GremlinWrangler
Well-known member
Looks like onehorse has some competition for his appallingly teensy peripheral series...
Nice layout, did it take many goes for the PCB fab to get all the milling right without things flying apart during machining?
Nice layout, did it take many goes for the PCB fab to get all the milling right without things flying apart during machining?
And moreover, flexibility in jumpers to choose chip selects.
Too bad we don't have an SPI like thing with addresses like I2C, instead of soldered-in chip selects.
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Thanks! Yep, I hope to have them up on Tindie in a couple days when the low profile headers come in.
The male header pictured on the side shot is missing its isolation, but the included headers will of course have the isolation.
unfortunately, the use in pin13 for spi-clk inhibits is use together with i2s, where pin13 is the only i2s0.rxdx0 possibility.
Not looking to compete, Onehorse is a really helpful guy and his little boards are great
This board is just something I designed to fit a certain way for my GSM board.
I have no idea if the fab had nay problems, but since they didn't say anything, I guess it went well. I'm really happy with the precision of the pads and milling.
This combo includes MicroSD, 10DOF (a slightly modified and thinner version of Onehorse's MPU9250 board), SIM slot, GPS, GPS, CANBUS, and a 12V step-down converter.
Overall stack height is only 14mm and most of the right side pins and one serial port are still unused.
Thanks! It won't work under the Teensy due to the 3V/GND headers blocking card removal/insertion, but I may make an upside down version in the future.
I have 0 experience with I2S, so this is something I didn't factor in.
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I'm pretty sure you can orient the SD socket opening to the side.
where did you get the pcb done?
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defragster
Senior Member+
CAD/Eagle is a dangerous thing - it could go on the bottom - it could use ALT SCK ... A flipped PCB rewrite to fit under could shrink two pins over the button hole. I'm on my way to starting ( I found this EAGLE Tutorial series on SPARKFUN )
I assembled a 32MB FrankB SerialFlash compatible design (small board in pic) that mounts twin 16M Flash chips on 7 pins teensy wide and 6 pins long.
It was part of an order I did to https://maker.works/ that is currently in ALPHA test mode:
I uploaded EAGLE Brd files - but Gerbers work - Odd thing for my first two orders totaling $19.17 shipped (almost 3 weeks delivery first order) is that the four copies of each were delivered as SIX - not sure how long the trend might continue:
Anyone looking to try out the service for some good looking 2 layer boards at low prices - or in my case make some mistakes for less money.
One shown is Frank's routed/castellated connector board and it matches the OSH dimensions as it should. A thinner board ( a good thing ) with gold plating.
It was $3.45 at OSH for 3 and $1.73 SHIPPED from Maker.works for 4 boards, and I got 6 delivered.
I assembled a 32MB FrankB SerialFlash compatible design (small board in pic) that mounts twin 16M Flash chips on 7 pins teensy wide and 6 pins long.
It was part of an order I did to https://maker.works/ that is currently in ALPHA test mode:
I uploaded EAGLE Brd files - but Gerbers work - Odd thing for my first two orders totaling $19.17 shipped (almost 3 weeks delivery first order) is that the four copies of each were delivered as SIX - not sure how long the trend might continue:
Anyone looking to try out the service for some good looking 2 layer boards at low prices - or in my case make some mistakes for less money.
One shown is Frank's routed/castellated connector board and it matches the OSH dimensions as it should. A thinner board ( a good thing ) with gold plating.
It was $3.45 at OSH for 3 and $1.73 SHIPPED from Maker.works for 4 boards, and I got 6 delivered.
This board is now up on Tindie https://www.tindie.com/products/Fusion/teensy-slim-micro-sd-card-adapter/
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