This is part of the RTC (Real Time Clock) subsystem, inside the LPC43xx chip on the Portapack hardware.

RTC Subsystem

The RTC subsystem keeps the actual clock (date / time) running, powered by a back up coin battery (which needs to be installed on the portapack board),even when the unit is not connected to an USB power source. And on top of this RTC functionality, the same coin battery will keep persistent a small region of VBAT-maintained SRAM (0x40041000, 256 bytes) for saving system state settings when the device is powered off.

The persistent memory map is defined at /firmware/chibios-portapack/os/hal/platforms/LPC43xx/lpc43xx.inc:

 **LPC_RTC_DOMAIN_BASE**       (0x40040000)
 **LPC_ALARM_TIMER_BASE**      (LPC_RTC_DOMAIN_BASE + 0x0000)
 **LPC_BACKUP_REG_BASE**       (LPC_RTC_DOMAIN_BASE + 0x1000) <-backup_ram region!
 **LPC_POWER_MODE_CTRL_BASE**  (LPC_RTC_DOMAIN_BASE + 0x2000)
 **LPC_CREG_BASE**             (LPC_RTC_DOMAIN_BASE + 0x3000)
 **LPC_EVENT_ROUTER_BASE**     (LPC_RTC_DOMAIN_BASE + 0x4000)
 **LPC_OTP_CTRL_BASE**         (LPC_RTC_DOMAIN_BASE + 0x5000)
 **LPC_RTC_BASE**              (LPC_RTC_DOMAIN_BASE + 0x6000)

backup_ram region

The backup_ram region is a small amount of ram (only 256 bytes), defined in /firmware/common/memory_map.hpp using the LPC_BACKUP_REG_BASE label, thus starting at address 0x40041000

data_t struct

The Portapack firmware uses the backup_ram region to store several uint32_t (and one uint64_t) variables, inside a struct, called "data_t", declared on /firmware/common/portapack_persistent_memory.cpp

Variables stored in persistent memory

Found in original portapack, but only carrying a few configuration variables, it was later expanded by furrtek's HAVOC version, incorporating several new configuration parameters.

Among those new variables, there is a uint32_t config_t used as storage for a few boolean flags.

On MAYHEM's version, we've added two new boolean configuration parameters, particularly useful for H1 users including "Speaker is present" and "Back Buttons on menus".

You can find them implemented as two new configuration checkboxes inside OPTIONS->UI.

These two new boolean parameters have been added into the uint32_t ui_config variable, Which now it is mapped as following:

ui_config Bit position / Description

• 31 (HAVOC)Splash screen
• 30 (HAVOC)Login
• 29 (HAVOC)Start in stealth mode
• 28 (MAYHEM H1 Branch)Place a back ("..") button in each menu
• 27 (MAYHEM H1 Branch)Use speaker output (H1 model accepts a speaker)

Using this two new booleans

They can be reached from anywhere by adding (if not already there) this include:

#include "portapack_persistent_memory.hpp"

and then you can check the configuration status for each parameter with:

portapack::persistent_memory::config_backbutton()

and

portapack::persistent_memory::config_speaker()

They return either TRUE or FALSE, depending on how they've been configured.