Here is the tutorial! Now bare with my horrible MS Paint schematics but it illustrates everything I did.
This tutorial assumes you have already are familiar with DreamPi and can solder.
Some these pictures I used from around the web one came from Whiteysnakey!
Parts and tools used:
- 330 ohm resistor
- 0.47 uF capacitor
- a diode I used 1N4741A which is 11V and 1W
- DC-DC boost converter
- Dell NW147 USB Modem
- Raspberry Pi Zero W
- 8GB micro SD
- soldering iron
- multimeter
Step 1: Unscrew your modem and separate the metal and circuit board from the plastic housing.
Step 2: You will have to get rid of the plastic posts that use to support the modem. I just used some pliers and was able to snap them off cleanly. I circled them in red.
Step 3: Remove the RJ-11 jack from the USB Modem. I cut the pins right at the jack and then there are two soldered connections on either side of the connector.
Step 4: I would wire everything to the backside of the Raspberry Pi Zero W like so. PIN 1 of the G2 connection supplies the 5V and then you just need a ground. I connected the power for the Pi here as it has some protections. Also connect the Data lines from the USB Modem like so.
Step 5: I soldered up the 330 ohm resistor, the diode, and the 0.47 uF capacitor to the DC-DC boost converter. Use a multimeter and adjust the pot to 9 Vs or so. pelvicthrustman runs his at 10.5 v so it doesn't have to be exact.
Step 6: It gets a little tricky here. You are going to solder the line voltage inducer, USB Modem and the Dreamcast Modem. The red line is PIN 3 and the green line PIN 4 on a RJ-11 connector. PIN 3 connects from the USB Modem PIN 3 to the LVI on both sides of the capacitor and then to DC Modem on PIN 3. The USB modem is nice and labels where 1 and 6 are. The dreamcast isn't but the above picture should be correct. PIN 4 is straight from the USB modem to dremcast modem.
Step 7: Connect power to the USB Modem and the DC-DC boost converter. I used the GPIO pins on the Pi to supply the power.
EDIT: The picture below has an error it has GPIO Pin 32 as a ground when it is Pin 30. Please make sure to adjust for that if you attempt this.
Step 8: Cover with lots of electrical tape to prevent shorts and place carefully inside the plastic case. In ended up placing the DC-DC boost converter over the Conexant chip but if your using a Model B it will be a Sega chip. The Modem was very close to the RJ-11 on the Dreamcast modem. The Raspberry Pi is right behind the USB modem.
Final thoughts - I haven't found a good way to configure the wifi without either connecting to the Pi with a Mini-HDMI or using another Pi and setting up the WIFI and then moving the SD Card over. I tried the wpa_supplicant.conf and OTG mode for the Pi to my desktop. I was thinking this might be more trouble than it's worth but if Dream Pi could create a hotspot that you could connect and then SSH to to configure everything that could be another solution.
I haven't found a good way to secure the metal outside to the modem so as of now I have just taped it. This is a snug fit so plan accordingly.
I hope this helps Deluxux or anyone else trying to recreate what I did. If you have suggestions to improve this please let me know.