Iota (TWL3025)

This is the Analog Baseband Chip TWL3025

It's very similar to its predecessors, the TWL3014 and TWL3016 devices.

A data sheet for the TWL3014 is available from
but forum registration is required for download.

It consists of various functions, including
  • ADC and DAC for the GSM baseband signals
  • ADC and DAC for the Voice/Audio path
  • DAC for APC (Automatic Power Control)
  • DAC for AFC (Automatic Frequency Control)
  • Battery Charging Controller
  • LDO's (Linear Power Regulators)

The functions of the ABB are controlled by a register set. The register set
is available through both USP and BSP.

External Interfaces

USP (uController Serial Port)

This is the SPI-like control interface between DBB and the TWL3025 (ABB).

The USP as measured on a C123 phone

TSP (Time Serial Port)

It is connected to the TSP controller inside the HardwareCalypso DBB.

The CLK6.5 Signal makes things a bit more complicated than we would like. The sequence of events is something like:
  • CLK_13M is applied continuously to TWL3025
  • nTEN is in default state of high (inactive)
  • internal CLK6.5 is in default state low
  • nTEN is asserted low by TPU, some 0..65ns before CLK_13M rising edge
  • next CLK13M falling edge starts first CLK6.5 rising edge
  • every falling edge of CLK13M toggles CLK6.5
  • TDR is sampled at every rising edge of CLK6.5 (including the first edge above)
  • 7 bits are transferred during seven rising edges of CLK6.5
  • TEN stays asserted for 1 CLK13M period after last bit is transferred
  • TEN needs to be released before next CLK13M rising edge to prevent another transfer

BSP (Baseband Serial Port)

This synchronous serial port is connected to the RIF (Radio Inter Face) of the Calypso DBB.

Debug traces

The chip has very tiny debug traces on a small flex-pcb around the 4 sides of the chip.
Which trace goes to which ball can be seen on this scan:

twl3025_usp.png - The USP as measured on a C123 phone (10.2 KB) laforge, 01/26/2010 06:56 PM