ESP32-PRO new IoT board with 4MB external RAM, 4MB external Flash, external crypto engine, LiPo charger


What you see above is our attempt to make ESP32 board with 4MB RAM. Reading the ESP32 datasheet this is quoted as the maximum possible external RAM possible to attach.

It’s named ESP32-PRO and here is the Github repo for it.

We encounter lot of problems while designed it, thanks to Rudi from for the tips and help. As there is the usual mess with the documentation and lot of unclear stuff.

We saw in the new WROVER-KITS we got that the module which is used is not WROOM, but WROVER and inside it has pSRAM.

The pSRAM is working on 1.8V and share same data pins as the Flash so we had to find 1.8V Flash also.

Another issue is that in the documentation pSRAM clock and data are reversed for unknown reason, but at least the software which run on WROVER module has these correctly set 🙂 so we had to ignore the Espressif datasheet and user manual info.

On top of this in the documents never mention that GPIO12/MTDI must be pull high if the power supply is 1.8V neither their reference design show this.

At least now having OSHW board with all correct settings will help other to not struggle all obstacle like us on the road to add external RAM.

We had to go to bare ESP32 chip as the RAM signals are not available on WROOM neither WROVER modules, this will lead to paid certification which we still do not know how much will be, but will have to add to the sale price of this module, so price is yet unknown but will be fair 🙂

As Rev.0 of the ESP32 chip has issue with cache for external RAM, we try to communicate with Espressif if we have to expect other bugs and issues with Rev.1 using external pSRAM, will keep you updated.

Beside the ESP32 we add PIC32MX270F256DT, this is nice processor with USB-OTG which will allow ESP32 to connect to both USB hosts and to act as USB-host and read for instance external USB Flash or take pictures from USB Webcam etc.

Why not AVR? Because AVRs are in trap of their own success. For the price of PIC32MX270F256DT which has 64K RAM, 256K Flash and USB-OTG you can buy ATMega32u4 which has only 2K RAM and 32K Flash and just USB device.

PIC32MX270F256 opens much more possibility with plenty of Flash and RAM.