It was around September 2004 when K managed to buy our first GSM modem from Wavecom for about S$480. We needed to go through a local distributor and traveled all the way to their office at Jurong to collect the modem.

After getting the modem, I started to try sending and receiving SMS using my own Serial Communication Tool:

serialtool

My Serial Tool was quite a handy tool for serial communication. It allowed me to type in any hexadecimal characters for sending, and I was able to create my own libraries of command sets so that I didn’t have to retype them repeatedly for testing.

Ok, enough self advertising.

From the AT command set documentation, I understood that there were two modes of sending and receiving SMS via GSM modem:

1. Text Mode
2. PDU Mode

The Text mode was the easier one to implement. However, unlike PDU mode, the Text mode did not support non-English SMS and concatenating of long SMS (more than 160 characters). After a discussion with K, we decided to implement the Text mode first in order to get the product out asap, because in Singapore most people communicate via English and at that time we thought that concatenation of long SMS wasn’t that important.

Using the Serial Tool, I tested the AT command sets for sending and receiving SMS to/from a few mobile numbers. If everything worked, I shall use the same underlying serial communication DLL for my new product. The testing process was very smooth and successful.

So after a successful proof of concept, we quickly proceeded to our next phase. I started to draft out the Requirements Specification and Design document, while K proceeded with preparing the admin and marketing stuffs.

Building a Product from scratch – Step 1: Proof of Concept

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