ADD On SRAM, with just an SPI SRAM. Useful for upgrading the amount of SRAM of modem NPR70 v04. Warning : do no use on other modem version (v02, v03 v05), because they already have the SRAM integrated. This add-on board fits on top of the Mbed-Nucleo, check pin names. This add-on is Highly recommended for Master (either Master-no-FDD or Master-FDD-down). Can also be useful for client modems. It increases the TX buffer length.