WiFi Module

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Introduction

There appear to be 3 WiFi modules at use in the DSi. These implement both the "old" WiFi chip (MM3315/MM3218) for DS-mode backwards compatibility, as well as a new Atheros 6k-based WiFi chip. The DS WiFi is configured through profiles 1-3 and is limited to 802.11b 1-2Mbps and WEP encryption while the Atheros supports 802.11g rates and WPA encryption, configured through profiles 4-6.

Next to the WiFi chips, these modules also carry the NVRAM chip. The DSi only uses a tiny portion of the 128KB available for startup data, calibration, and user settings. Newer revisions of this board have a SPI EEPROM that has no backing memory for most of the 1Mbit address space (presumably as cost savings?). Thus, older modules can be used for installing the "dslink" WiFi loader (to be launched in DSi mode via save-game hacks in DSi hybrid games), while newer modules require a hardmod (chip replacement) to achieve this (as demonstrated by khmann, using an ST M34PE20 chip as replacement). All revisions of the module have footprints for both large and small NVRAM chip, and the change to the limited chip occurred prior to the release of the dslink exploit.

The Mitsumi WiFi is controlled through data in the NVRAM (eg: calibration data, allowed channels), while the Atheros configuration is stored in the other tiny IC on the board, an I2C EEPROM.

The pinout of the connector can be found in FCC documents (see below). This connector includes pins for JTAG access to the Xtensa core in the Atheros chip (using 3.3V signals, though the 1.8V rail needs to be supplied from an external source as well). It presumably uses the same debug interface as found in the ESP8266 and ESP32 chips (which also use Xtensa CPUs), though no reports of people attempting to connect to it have been found at the time of writing.

If this module is disconnected the DSi turns on to a black screen, because it can't read the NVRAM. If the DSi doesn't like the data contained on the module it will give either error 0000FEFE or 0000FE00 at poweron. See stage1 for more information.

Models

The original DSi DWM-W015 module features two wireless chips; a Mitsumi MM3218 for DS compatibility and a more modern Atheros AR6002G BGA which share the antenna through an RF switch. It also features 1Mbit of SPI EEPROM (Media:STM45PE10.pdf) for NVRAM. It has enough space to store a full copy of the old DS firmware.

The updated DWM-W015A module uses a tiny "5A32" chip as NVRAM (UDFN/XSON, as opposed to the SOIC-sized chip in the older revision). Only the first and last few memory blocks are actually backed by a nonvolatile memory, other addresses return garbage.

The DSiXL or DSi/LL module is labeled DWM-W024, and includes only an Atheros AR6013G-AL1C, a 5A32 variant, empty SPI flash pads, and another small chip, the Atheros-native I2C configuration. For reference, the 3DS DWM-W028 module is reported to use an Atheros AR6014G-AL1C. The connector pinout is unchanged. These AR601x chips contain the combined functionality of both the AR6002 and MM3218 chips found on the DWM-W015.

Photos

DWM-W015

http://www.flickr.com/photos/micahdowty/3846960965/sizes/o/in/photostream/

DWM-W015A

DWM-W015a.jpg

Note the circle in this image shows a 10k resistor from pin 5 WP to GND, which the ST M45PE10 datasheet indicates will write-protect the first 64K. To disable this protection according to the SPI datasheet, remove the resistor and solder pin 5 to pin 6 VCC.

DWM-W024

Dwm-w024.jpg

Documents and external links

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