First sign out of messages on ipad and reboot the device by pressing and holding both the home and power buttons at the same time until the apple logo appears, then let go.
Do the same for phone, reboot then sign into messages and set up with phone number.
Now set up messages on ipad with same apple id that has iphone number assigned to it.
It now should show up on ipad as the send/recieve number
The trick is that you have to set up on phone before setting up messages on ipad.
Using FaceTime http://support.apple.com/kb/ht4319
Troubleshooting FaceTime http://support.apple.com/kb/TS3367
The Complete Guide to FaceTime + iMessage: Setup, Use, and Troubleshooting
Troubleshooting FaceTime and iMessage activation
Using FaceTime and iMessage behind a firewall
iOS: About Messages
Set up iMessage
Troubleshooting iMessage Issues: Some Useful Tips You Should Try
Setting Up Multiple iOS Devices for iMessage and Facetime
FaceTime and iMessage not accepting Apple ID password
Unable to use FaceTime and iMessage with my apple ID
My Facetime Doesn't Ring
For non-Apple devices, check out the TextFree app https://itunes.apple.com/us/app/text-free-textfree-sms-real/id399355755?mt=8
How to Send SMS from iPad
Note:To receive iMessages sent to your phone number on your iPad, iPod touch, or Mac, you must meet the following requirements:
- iPad or iPod touch using iOS 6 or a Mac using OS X 10.8.2.
- Verify that you are signed in to your Apple ID account on Settings > Messages > Send & Receive.
Well, I guess it can't be set on iPad 1
However, I still wonder how it worked so far, interesting.
Hi Sokuya. Having an iPad first gen running ios 5.1.1 just limit imessage sent or received from or to your telephone number. You can set up to receive/send to your email addresses and telephone number. If you need to have your imessage conversations in all your devices you must tell your contacts to use your email address to send imessages. Otherwise any imessage sent to your telephone number will be sync only between idevices running ios 6.
I have an iPad first gen too along with an iPod 4 and iPhone 4s. I have imessage set up with my telephone number and 3 email addreses. No primary caller id, the four are in the same hierarchy. So they sync perfectly. About the different threads issues, I don't understand. The thread depends wether you are texting in imessage or as sms. In first gen iPad you would only be reached by imessage....
hope this would help.