Related links

This page describes the printed circuit board of the phone. Related information can be found on the generic GXP page and on the GPIO page.

Occurrence of this PCB

The GXP2020 PCB is used in the following device models:

• GXP 2020

This manufacturer also produces other models.

Components found

• DSP system-on-chip: Covered in paint. This is a TMS320VC5501PGF.
• A coprocessor 320AIC20K from Texas Instruments interfaces speaker, microphone and line in/out to the DSP over I2C or S2C. It includes support for oversampling and filtering.
• Flash memory: 1024k x 16, or 2048k x 8: EN29LV160AB-70TCP. Its 70 nS cycle time makes this flash memory suitable to run programs from, so a smaller RAM size is possible.
• SDRAM: 2048k x 16, or 4096k x 8: 2x W9816G6CH-6. Supports speeds up to 166 Mhz.
• Ethernet: RTL8019AS and on the models with a second ethernet connector also (TODO). The RTL8019AS is an NE2000 clone, albeit a bad one according to the Linux kernel. It does not really matter; at least example code is available in that kernel, and actually uIP has already been ported to these chips before.
• Switch: RTL8305SC with support for 5 ports, with up to 2 MII ports. It would seem that the DSP processor needn't concern itself with passing traffic between the LAN and WAN interfaces. It is even possible that the DSP processor is fully unaware of any network hardware other than the main ethernet device.

Connectors found

These are described centrally in more detail:

• J401 is a JTAG connector TODO:VERIFY which looks the same as on BT200 boards
• EXT is an I2C connector, including 3V3 supply and pins to influence booting over I2C. I've been looking everywhere for I2C but never expected to find it externally accessible ;-) but in fact it makes a lot of sense -- for an extension connector.

The JTAG connector used in these Grandstream phones is a 14-pin connector. Its solder islands are open on the PCB, so soldering in a 0.1" pitched two-row pin header is easy.