Update doc

README.md

@@ -7244,32 +7244,21 @@ Comes from the [Unicode UTF-16 Encoding](https://en.wikipedia.org/wiki/UTF-16) o
 
 _Why send SMS in PDU Mode instead of Text Mode?_
 
-- TODO: More reliable (304 Invalid PDU)
+Sending SMS Messages in Text Mode looks easier. But we should use PDU Mode instead. Here's why...
 
-- TODO: UTF-16 Encoding
+TODO PDU Mode works more reliably (304 Invalid PDU)
 
-- TODO: Receive messages
+```text
+// Text Mode: How many characters in this SMS?
+AT+CMGS="yourphonenumber"
+```
 
-  ```text
+TODO
-  // Select Message Service 3GPP TS 23.040 and 3GPP TS 23.041
-  AT+CSMS=1
-  +CSMS: 1,1,1
-  OK
 
-  // Set SMS Event Reporting Configuration
+```text
-  AT+CNMI=1,2,0,0,0
+// PDU Mode: 41 bytes in this SMS (excluding SMSC)
-  OK
+AT+CMGS=41
-
+```
-  // Message is dumped directly when an SMS is received
-  +CMT: "+8615021012496",,"13/03/18,17:07:21+32",145,4,0,0,"+8613800551500",145,28
-  This is a test from Quectel.
-
-  // Send ACK to the network
-  AT+CNMA
-  OK
-  ```
-
-  [(EG25-G AT Commands, Page 167)](https://wiki.pine64.org/wiki/File:Quectel_EC2x%26EG9x%26EG2x-G%26EM05_Series_AT_Commands_Manual_V2.0.pdf)
 
 # Compile NuttX on Android with Termux