uSD pins on STM32 - Page 1
Forum section: electronics / general

author: benyB
author_rank: Newbie
timestamp: July 30, 2018, 01:43:40 am
content: Hi , I'm trying to put 2 x SD card slots on STM32F7xx. I can use the usual D0,D1,D2,D4 pins available for one card SDMMC2 but the second card 'SDMMC1' I only have D0,D4,D6,D7 pins available.The thing on SDMMC2 D2,D3 pins has to stay there..Does anyone familiar with STM micro's know if this is allowed as long as the GPIO is defined correctly?or do I have to start with pin D0 and go up sequentially?I'd normally just ask on the STM32 forum , but its down , yes not a great sign for a hardware company)I'd like to get my 4 layer proto design off to the factory and this is the only thing holding me back !

author: JS
author_rank: Frequent Contributor
timestamp: July 30, 2018, 03:07:37 am
content: Can't you breadboard it before ordering? At least at slow transfer speeds to see if it can work...JS

author: benyB
author_rank: Newbie
timestamp: July 30, 2018, 12:38:31 pm
content: 208 pin stm32f769, maybe i could get an adapter board, tricky..The stm32f769i-discovery does'nt break out the pins i'm looking at. I'll try email STmicro i think. Will report back if i get an answer.

author: JS
author_rank: Frequent Contributor
timestamp: July 30, 2018, 02:03:07 pm
content: Bummer! The discovery kits are nice but they should break out every pin, 208 are a lot but they could use an odd connector to do so, or an edge connector if they are feeling cheap...JS

author: benyB
author_rank: Newbie
timestamp: July 30, 2018, 03:40:07 pm
content: Yer , they should break out every pin to test pads at least.To be fair theres a ts screen audio codec 4 mics RAM QSPI SDMMC HSusb HOST ethernet etc all connected so maybe the routing was just to hard to break everything out on top of that. or , more likely they just needed a reason for the 350$ STM32F769I-EVAL with Jtag etcThe discovery board CPU is BGA so otherwise I'd just tack on some fine wire to the IC leads ! its only 2 wires ! like you say , even if I could try it a low speed it would be enough !

author: benyB
author_rank: Newbie
timestamp: July 30, 2018, 04:38:37 pm
content: I tried cubeMX ( there pin config software ) and it looks like you have to stick to D0,D1,D2,D3 for 4bit SDcard. Its probeblysomething to do with DMA.theres another version of the chip with no DSI controller and less flash memory that might work for me.

author: JS
author_rank: Frequent Contributor
timestamp: July 30, 2018, 06:41:09 pm
content: Do you need to use them both at the same time? Do you need high speed on both cards?You might be able to use both on the same bus with a switcher, but software could be tricky... Or you could use the secondary one with bit banging uf you can spare the time and speed.JS

author: benyB
author_rank: Newbie
timestamp: August 04, 2018, 12:24:57 am
content: I need to use both cards at the same time. I thought of mirroring them ( shared pins and one channel ) but that wouldn't really work.I need 2 x channels really.Do you mean bit banging over other GPIO pins? the DMA is mapped for uSD1 or uSD2 so not really sure I could do that.Also probably beyond my coding ability to start writing raw machine code / bit banging !