Overview of an Operational WiFiBoard

This video was made to to help @indigi_newton with troubleshooting his wifi card build. Even though the video is from the perspective of helping a single person troubleshoot a card, it is still a nice overview with a demonstration of it working in a Newton.

Files published to GitHub

You can find the files for this project in GitHub: https://github.com/jake-b/Newton-Internal-WiFi

3D Printed Port Cover

Since the MP2x00 did not come with an internal modem (and one was never sold), each MessagePad came installed with a little plastic cover that fills the space where the RJ-11 jack would be.

This is the same cover where apple would place a "2100" sticker indicating that a MP2000 was upgraded to a 2100.

Due to an oversight, the WiFi card extended into the area where this plastic cover would sit.  (I'm not sure this could have been avoided, even if I had planned ahead)

Instead, I've designed a replacement cover that does not interfere.  For good measure, I added an embossed WiFi logo to indicate that the internal WiFi card is present.

I think it makes for a nice finished product.

The STL files for the port cover can be found here: https://github.com/jake-b/Newton-Internal-WiFi/tree/master/Port%20Cover

WiFi Board v1.1

I got the revised boards and finally found some time to assemble a board.  This board adds a logic inverter to fix the flow control, and removes some extra traces for an alternate reset circuit.

To assemble the board, I had a stencil made and used it to apply solder paste.  Then I placed the components using a very simple "pick and place" rig:

This jig was made from a piece of brass tube, a leur lock fitting, some tubing, and a 22ga blunt dispensing needle.   It was mounted in a cheap USB microscope holder (available on eBay or Amazon) and hooked to a vacuum pump that I already had.   There are many more complicated versions of this rig on the internet, but this simple setup worked fine for me.

Finally, I baked it in a toaster oven that I got for free at a garage sale, and a rocket scream reflow shield.

Everything works great.  I consider this project a success.  All thats left to do now is to 3D print a replacement for the plastic "plug" that covers the hole in the case.

Finally, a little application that uses the method mentioned in an earlier post to enable the board when the 'modem' port is opened:

Thermal Performance and Loose Ends

Thermal

Early designs used a linear regulator to supply 3.3v from the Newton's battery voltage.  It became pretty obvious that a linear regulator would get too hot, and so I changed it for a switching regulator.

I wanted to do a real world test.  The WiReach specs say that it can draw around 350mA peak during transmit.  I modified the Thumb sample code into a program that would output a continuous stream of ~25kB packets.  I taped a thermocouple to the regulator and ran the test for an hour or so.

The results were promising.  From room temperature, the regulator went from 77.4F to a high of 85.1F.  This satisfies me that in my normal use the board will not overheat.

A wise man once told me:

"People might be using such a Newton on a camp site close to Death Valley in August. Before you release such a circuit into the wild, you should put the assembly into the baking oven at 60 degrees centigrade and see what happens..."

Good advise, but I don't think I'll be performing that test.  I just can't imagine putting a Newton in a oven for any amount of time.

This test is anecdotal at best, I guess.  Was the WiReach module anywhere near its peak transmit power or current draw?  I don't know.  At 115200bps, I'm not sure that the Newton can saturate the WiFi module such that it would need to draw its maximum.

Physical

I found one other minor issue with the physical design.  I intentionally pushed the module as close to the edge of the Newton as possible-- into the space where a telephone jack would have been for an internal modem.  The module is large and getting it in just the right place and keeping the board within a 5cm square took some trial and error.  Also, I wanted the antenna area as close to the edge of the case as possible.

Well this made for one unintended consequence-- the "plug" that covers the hole likely won't fit, and it will interfere with the WiReach antenna connector and board.   It isn't the end of the world really -- I intend to 3D print a new plug with a little more clearance, and maybe an embossed WiFi logo so you can tell from the outside that there's a WiFi card installed.

An ugly fix

It is ugly, but it works:

I soldered leads to a 1-gate logic inverter.  This wasn't easy because the part is so small.  Then connect it to 3.3v, GND, and the RTS line coming out of the WiReach.  Then I cut the RTS trace on the bottom of the board.  I connected the output of the inverter to the input of the line driver IC.

Some Kapton tape holds it all in place.   It is a really terrible hack, but it works.  Hardware flow control works as expected, now.

I'm going to design a version 1.1 of the board that includes the inverter.  Also I can remove the extra GPIO/Reset stuff since the "power good/reset" circuit works.

WiFi Board For Newton: A Success?

I'm going to call this one a success.

There is an error in the hardware flow control circuit, but that's due to an error in the N2 Platform documentation.  I'll take responsibility because I should have more thoroughly prototyped (which I thought I had, but oh well)  I'm still planning on hacking an inverter onto the board to fix the issue.

Even so. I'm chalking this one up as a success.

A few last details:

The Antenna

I found a really small antenna.  I think its really for bluetooth devices, but it seems to work fine.  It is so small, I was able to tuck it in a small gap between the power connector and the interconnect port.

WiReach Configuration

You need to send a few specific commands to configure the WiReach module.  The most important is AT+iWANS=1  which tells the WiReach that the WiFi network is the WAN subnet.  Also you need to configure a username and password (which matches the PPP configuration on the Newton.)  AT+iRAU and AT+RAP are the commands you use to set the username and password.  And of course you'll need to connect to your network using:

AT+iWLSI=My_WiFi
AT+iWST0=4
AT+iWPP0=<WPA2 passphrase>

I use PT-100 to configure the module.  Then a Serial Internet configuration with a script.  The script is simple.  First, it pauses for a few seconds to give the module time to power on.  Second, it sends the at+iSPPP:0 command to start the PPP server.  Finally, it waits for the OK.

How Does it Work?

My goals when I started this were:

• The case had to close and everything had to be fully internal.  
• Find an antenna and antenna placement that would work without modifying the case or the shielding.
• Enough range to reach my router from my couch...
• Connecting my Newton to a WPA2 network.

In all, despite the flow control thing, I'm pretty happy with the end result.  The project meets my requirements.

I'm trying to decide if I want to do a v1.1 board with corrected flow control signals.