Add GPRS REST API to 8051

My existing Keil-C firmware for an AT89S52 (8051 core) already handles SMS and voice calls through a SIM800L module. The hardware set-up is fixed—4×4 keypad, 16×2 LCD, 24C16 EEPROM, plus the SIM800L on UART. Now I need the same board to push data to the cloud over GPRS instead of relying solely on SMS.

Scope of this update
• Rework the SIM800L driver layer to open a GPRS session, handle PDP context, and perform REST transactions (HTTP GET/POST as needed).
• Call only two REST endpoints; the URL pattern embeds the device’s serial number as a variable, e.g. http://myserver.com/api/{SN}. No SOAP or GraphQL—pure REST.
• Direction is one-way: the device just sends data; no need to parse server responses beyond basic 200-OK checking.
• Keep all existing call/SMS features intact; keypad, LCD, and EEPROM routines are stable and should not be touched except where you need to display status or store APN credentials.

Deliverables
1. Updated, well-commented Keil project files (.c, .h, UVPROJ) that compile without errors on uVision.
2. A brief read-me describing new functions, memory usage changes, and AT command flow.
3. Demo log (UART capture) showing successful GPRS attach and REST requests to both APIs.

I will provide the current source, serial-number format, APN details, and test credentials once we start. Looking for someone who has already wrestled with SIM800L AT commands on Keil and can turn this around quickly and reliably.