Advertisement
Quick Links
CML Microcircuits
COMMUNICATION SEMICONDUCTORS
AN/2WR/7031/FRS/3 July 2007
1 Introduction
The CMX7031 is a highly integrated baseband processor that is targeted at analog two way radio
applications. Professional and leisure radio designs can benefit from the extensive functionality, low
power consumption, and aggressive pricing offered by the CMX7031. Additionally, the ability to
enhance its functions through updated Function Image™ files allows the CMX7031 to offer enhanced
features for no additional cost.
The purpose of this application note is to illustrate how the CMX7031 can be configured for a feature
rich "family radio" product. This document will describe how the CMX7031 can be configured to
perform the following functions:
•
Half Duplex voice communications
•
Text Messaging (both open and private messages)
•
GPS location data
•
Unique 'ring tones'
•
Audible alerting tones, for example indicating when a button has been pressed
•
'All Call' (urgent) call capability
•
RF Synthesizer configuration
•
System clock configuration
This document reflects the CMX7031 device functionality after being loaded with Function Image 1.3.
Use of this document with other Function Images™ may result in undesired operation. Discussion of
Function Image™ loading procedures is beyond the scope of this document and is fully discussed in
the CMX7031 datasheet.
The following information should be consulted while reviewing this application note:
1. CMX7031 Datasheet
2. CMX7031 User Manual
3. CMX7031 Synthesizer Calculator Application Note and Spreadsheet
© 2007 CML Microsystems PLC
Application Note
An Example Core Design for a
Complete Family Radio
1 of 28
CMX7031:
AN/2WR/7031/FRS/3 July 2007
Advertisement
Related Manuals for CML Microcircuits CMX7031
Summary of Contents for CML Microcircuits CMX7031
- Page 1 Function Image™ files allows the CMX7031 to offer enhanced features for no additional cost. The purpose of this application note is to illustrate how the CMX7031 can be configured for a feature rich “family radio” product. This document will describe how the CMX7031 can be configured to perform the following functions: •...
- Page 2 Application Note CMX7031 : An Example Core Design for a Complete Family Radio Table of Contents Introduction............................. 1 CMX7031 Function Image™ 1.3 Feature Set................. 3 Description of Scenario ........................4 Transmit Functions ........................ 4 Receive Functions ......................... 5 Assumptions .......................... 6 Block Diagram ........................
- Page 3 Application Note CMX7031 : An Example Core Design for a Complete Family Radio 2 CMX7031 Function Image™ 1.3 Feature Set In addition to being backward compatible with previous Function Images, Function Image™ 1.3 loads the following functions into the CMX7031: Base configuration •...
- Page 4 1. An audible alerting tone will be generated by the CMX7031 so the user knows a button was pressed. 2. The CMX7031 will transmit an FFSK / MSK data burst to the remote user. This FFSK / MSK data burst will instruct the remote user to transmit its location data back to the calling radio.
- Page 5 The user can press the radio’s “Monitor” button to listen for all activity on a channel. When this happens: 1. An audible alerting tone will be generated by the CMX7031 so the user knows a button was pressed. 2. The CMX7031 will activate its audio output amplifier to allow any received signal to be passed to the radio’s speaker or headset.
- Page 6 RSSI threshold and hysteresis settings. • RF discriminator output is applied to CMX7031 DISC pin. • CMX7031 AUDIOOUT pin delivers ring / alerting tones and recovered voice to an external speaker driver amplifier for presentation to the radio speaker. • RF Synthesizer FRS Channel 1 = 462.5625MHz, used for Tx and Rx.
- Page 7 AUXDAC2: Tx power amplifier temperature compensation control voltage AUXDAC3: TCXO temperature compensation control voltage AUXDAC4: Not used The normal operating mode for the CMX7031 in this application is powered down, monitoring RSSI with ADC1 (STATE 3 from Figure 6). 3.4 Block Diagram...
- Page 8 Table 1: RF Channel Data ($B2) Settings for Channel 1 Synthesizer The second synthesizer in the CMX7031 is used to generate LO1 signal for the RF to IF1 downconversion. The following table illustrates the register values needed to configure the CMX7031 Channel 2 Synthesizer to generate this LO frequency: ©...
- Page 9 , which translates from 0.33V to 2.97V in this application. Rolling averaging is used with the CMX7031 ADCs in this application. With this averaging method, a fraction of the current ADC input value will be added to the previously calculated ADC reading.
- Page 10 A tradeoff exists between response time and noise immunity, and the optimal averaging setting is application dependent. This application scenario monitors battery voltage so that the host microcontroller can be alerted to a weak battery condition. The battery voltage will normally exceed the CMX7031 V of 3.3V, so the © 2007 CML Microsystems PLC...
- Page 11 For the purposes of this document, the battery voltage applied to the CMX7031 ADC is 40% of its actual value. For example, a low battery condition of 3.6V is presented to AUXADC 2 input pin as 1.44V.
- Page 12 This example application uses an external 19.2MHz TCXO to derive the system clock outputs and the CMX7031 main clock signal. Since the external TCXO frequency is not the default 6.144MHz value, adjustments to Programming Register blocks P3.2 through P3.7 are required to ensure proper operation.
- Page 13 Table 6: Estimation of Data Throughput for Type 5 Message Format Each 8-bit character has 4 bits of FEC automatically added by the CMX7031 in Type 5 message format. As can be seen from the table, 190 8-bit characters can be transmitted in one second using the robust Type 5 message format.
- Page 14 User defined value is loaded into TX DATA Register ($CA), b15..8. Range of valid address is 1-255 (decimal). Format Byte Automatically generated by the CMX7031; value depends on b7..5 of MODEM CONTROL ($C7) Register. User defined, value is loaded into TX DATA Register ($CA), b7..0. Range of...
- Page 15 Input Gain and Output Signal Routing ($B1) register.) For the purposes of this example, the external components surrounding the CMX7031 input amplifier are configured for unity gain. Therefore, the input level for the Input 1 or 2 internal amplifier is as follows: •...
- Page 16 With P1.0 b0 = 0, the resulting value for P1.0 is 0xD6D6. 4.7 Receive Signal Level Considerations The CMX7031 audio output driver has a minimum load resistance rating of 20kΩ, so an external speaker driver will be required. For V = 3.3V, the maximum audio output level from the CMX7031 is:...
- Page 17 Input Gain and Output Signal Routing ($B1) register.) For the purposes of this example, the external components surrounding the CMX7031 input amplifier are configured for unity gain. Therefore, the input level for either Input 1 or 2 internal amplifier is as follows: •...
- Page 18 The value of 0xD is then loaded into b9..4 of P1.1. 5 Operating States There are several possible operating states for the CMX7031 in this application. The following state flow diagram illustrates the possible transitions between the various operating states.
- Page 19 Image™ loading procedure is discussed in Section 7.3 of the CMX7031 datasheet. After the Function Image™ has been loaded, the CMX7031 will report back checksum values as well as its product identification code. The host microcontroller should verify that these values are correct.
- Page 20 P3.1 = 0 (default ADC2 averaging length). PROGRAMMING REGISTER (P3.2) 0x7018 PROGRAMMING REGISTER (P3.3) 0x7099 PROGRAMMING REGISTER (P3.4) 0x70C8 These writes configure the CMX7031 to use the 19.2MHz TCXO as its main clock source. PROGRAMMING REGISTER (P3.5) 0x7200 PROGRAMMING REGISTER (P3.6) 0x7140 PROGRAMMING REGISTER (P3.7) 0x7008 PROGRAMMING REGISTER (P4.0)
- Page 21 5.3 STATE 3: Sleep This is the default operating state for the CMX7031 in this application. In this condition, the CMX7031 is in idle mode and powered down to the maximum extent possible while monitoring for incoming carrier. Highlights of STATE 3 are as follows: •...
- Page 22 5.4 STATE 4: RX Startup In order to reach this state, incoming RF carrier has caused the RSSI signal to exceed the CMX7031’s ADC1 high threshold. When this happens, STATUS Register ($C6) b8 = 1 and an IRQ is issued.
- Page 23 Tx mode are passed through the Tx Limiter, so Programming Block P4.7 (Tx Limiter Control) must be set to a nonzero value in order for an audio tone to come out of the CMX7031. The Tx Limiter does not affect audio tones generated in Rx mode.
- Page 24 Table 12: STATE 6 Register Settings 5.7 STATE 7: FFSK / MSK Rx At this point, the CMX7031 has detected the presence of RF carrier and 2400 bps FFSK / MSK signals. The CMX7031 is configured to receive this FFSK / MSK message as follows:...
- Page 25 2400 bps FFSK / MSK enabled, Tx mode. Table 14: STATE 8 Register Settings The CMX7031 will issue interrupts when additional Tx data is required. Once a “data transfer required” interrupt is received, the host must load new data before the current data has been transmitted;...
- Page 26 : An Example Core Design for a Complete Family Radio 5.9 STATE 9: Voice Tx To reach this point, the CMX7031 has transitioned from the Sleep state (STATE 3) and the Ring Tone Tx state (STATE 5). Highlights of this state include: •...
- Page 27 The purpose of this document was to illustrate how the CMX7031 can be configured to perform such features in a real application. It is hoped that this document will assist the designer in developing exciting new products based on the CMX7031.
- Page 28 Application Note CMX7031 : An Example Core Design for a Complete Family Radio CML does not assume any responsibility for the use of any circuitry described. No IPR or circuit patent licenses are implied. CML reserves the right at any time without notice to change the said circuitry and this product specification.
Need help?
Do you have a question about the CMX7031 and is the answer not in the manual?
Questions and answers