Ezurio BISM2 User Manual download pdf

Application Note

APN06004

Extracting the Crystal Oscillator Output from a BISM

Overview

This application note describes the process to obtain a crystal oscillator output from one of the

Analogue pins on a BISM2 module. This can be used to drive an external microprocessor,

removing the need for a separate crystal oscillator.

1. Introduction

The BISM2 Bluetooth Module is capable of outputting a clock signal from its onboard crystal

oscillator. This can be used by developers to power external circuitry, such as a microprocessor,

reducing the overall component count. The crystal output is available on the AIO1 Analogue

Output Pin.

To enable this feature, one of the PSKEYs in the CSR BlueCore04 chip needs to be modified. This

requires the use of the SPIbus in conjunction with CSR’s PSTOOLS application to reprogram the

BISM. Once programmed the change is permanent unless reset by the same application. This

programming cannot be performed via the UART port or AT command, but requires the use of one

of EZURiO’s Development kits or a direct link to a PC via the application’s motherboard. The SPI

pins are available on the 40 way Hirose connector. If designers wish to use this feature as part of

production build, they should consider routing these pins to a programming connector.

2. Procedure

Connect the module’s SPI bus to a PC that has a copy of CSR’s PSTOOLS and power it up. Then

start PSTOOLS and check the connection to the module is live.

Enabling the crystal Oscillator output requires the manipulation of the AMUX_AIO1 key (Decimal

1056, Hex 0x420). In most version of PSTOOLS this is not displayed, so start by changing the

View to Programmer ID’s.

APN_06004_1v0 Crystal Output from BISM.doc Page 1

1 2 3

Page 1

Application Note APN06004 Extracting the Crystal Oscillator Output from a BISM Overview This application note describes the process to obtain a

Now enter AMUX into the Filter box and select AMUX_AIO1. The select from list entry box does not generally provide options for enabling crystal osci

3. Limitations The following limitations should be noted. • The crystal output is not available when the BISM is placed into sleep mode. • The cry

Ezurio BISM2 User Manual