STM32F7 discovery SDRAM

[manuel239955_stm1_st]

Posted on November 07, 2015 at 15:11

Hello,

Why only 64Mbit are accessible on the board ? Why the board was not designed with 16bit-wide SDRAM ?

[Tesla DeLorean]

Posted on November 07, 2015 at 15:45

Price and availability?

[Torsten Jaekel]

Posted on December 08, 2015 at 01:52

Pls., see schematics (and Discovery manual): a 32bit Micron SDRAM, where the upper 16 Data Lines are not connected. Therefore just half the size available.

Otherwise, we would not have enough IO Pins available, Arduino header would not be there. (not a question of costs, more which GPIO do you want to have left for the user)

[Tesla DeLorean]

Posted on December 08, 2015 at 05:30

The question had two main points a) why's half the bus missing, b) why not use a 16-bit device with the full capacity.

And my point was that it was still probably more cost effective to throw away half the bits in the 32-bit device, than find/source/sustain a 16-bit wide one. The STM32 are heavily pin constrained, especially with SDRAM+LCD, and this sure beats the hack of using an I2C expander like the EVAL boards.