Monday, September 12, 2011

Freescale MC13260 SoC Two-Way Radio IC

Found this in a mailing-list post the other day. Very neat, it's a System-on-Chip that is almost everything you need to make a radio from 60MHZ-960MHZ.

From the Freescale website:

Target Applications:
Comprehensive analog FM radio
Comprehensive digital radio (DMR, P25, TETRA, dPMR)
Dual-mode analog FM and digital voice/data
"Talk around the network" feature for cellular applications


ARM926EJ-S™ MCU operating at clock speeds up to 150 MHz
Modem processor (software-defined radio) operating at clock speeds up to 100 MHz
640 KB of integrated RAM
MCU peripherals to support control and monitoring functions
High-performance integrated RF transceiver supporting RF frequencies of 60 MHz–960 MHz
Fully integrated, high-performance RF fractional-N synthesizer
Integrated 13-bit audio CODEC with analog input/output
Three 12-bit DACs for support functions
10-bit general purpose ADC with four multiplexed inputs
Receiver supports linear modulation
Linear transmit support using integrated I and Q DACs and an external modulator
Advanced Encryption Standard (AES) module for secure communication
Full-speed USB device with integrated PHY

Pretty feature rich! I assume the RF components you need amount to bandpass filtering, preamp, transmit/receive switch, and filtering, power amp for transmit side. This chip implements the SDR conversion, AD/DA conversion, etc. It has an ARM9 CPU and a separate "modem" DSP. I'm unclear if the DSP handles the FM mod/demod and any modem processes such as encoding or decoding PSK, FSK, GMSK, QAM, etc.

This chip is pre-release, according the press release the chip will be available in Q1 2012.

Press Release:
Product Details:
Fact Sheet:
Support Info:
Product Brief:

Other chips I've covered include:
CMX7163 QAM Modem
The CMX7163 QAM Modem is a low power half-duplex device supporting multiple channel spacings under host microcontroller (µC) control. Its Function Image™ (FI) is loaded to initialise the device and determine modulation types.
The 7163FI-4.x supports 4-, 16- and 64-QAM modulations up to 96kbps in a 25kHz channel, with channel estimation and equalization to provide robust performance under realistic channel conditions.
Flexible bit rates support a wide range of applications requiring a selectable bit rate and robustness.

An integrated analogue interface supports 'direct connection' to zero IF I/Q radio transceivers with few external components; no external codecs are required.TI CCxxxx series
From my blog post on the Ubertooth One:

A CC2591 2.4ghz PA/LNA,CC2400 2.4ghz RF transceiver and a LPC175x series ARM chip.
What inspired him to use a chip like the CC2400? He previously played around with a kids toy called an IM-ME. It's a pink pager-like device meant for girls to send instant messages over the Internet (via a usb dongle plugged into a computer)... He was able to turn it into aninexpensive spectrum analyzer type device. How? It has a CC1110 chip. This is an RF transceiver chip with an integrated 8051 cpu. According to the linked site:

Frequency range: 300 – 348 MHz, 391 – 464 MHz and 782 – 928 MHz
Pretty neat, it's capable of operation in the 70cm and 33cm bands at up to 500kBaud. This was in a toy that was less than $20 on ebay.

Raspberry Pi ARM Single-Board Computer

This is the Alpha prototype board according the the wiki.

This is a very low cost ARM SBC that is being developed right now. It is unreleased but once it comes out, there could be a multitude of applications in Ham Radio for it. They are talking about making two versions, Version A for $25 and Version B for $35.
Here are the "Provisional Specifications" from the community written wiki

  • 700MHz Broadcom media processor featuring an ARM11 (ARM1176JZF-S) core, Broadcom GPU core, DSP core and support for Package-on-Package (PoP) RAM
  • 128MiB (Model A) or 256MiB of SDRAM (Model B), stacked on top of the CPU as a PoP device
  • OpenGL ES 2.0
  • 1080p30 H.264 high-profile decode
  • Composite and HDMI video output
  • One USB 2.0 port provided by the BCM2835
  • SD/MMC/SDIO memory card slot
  • General-purpose I/O (About 16 3v3) and various other interfaces, brought out to 1.27mm pin-strip
  • Optional integrated 2-port USB hub and 10/100 Ethernet controller (Model B)
  • Open software (Ubuntu, Iceweasel, KOffice, Python)
  • Capability to support various expansion boards

Anyone's guess if it will come out at the price point they are hyping up. In my experience stuff like this tends to slip into higher price ranges when people get excited about it. Kinda like electrons jumping into higher orbits.

Besides including 256MB RAM, the B version is also suppose to have a chip on board that is a 2-port USB hub and ethernet controller. I'm assuming the ethernet will also use your USB bandwidth.

It is interesting to me that they are stacking the RAM chips right on the processor. That should save some space at least! The Broadcom SoC seems to be pretty neato too. It has the ARM11 CPU, a GPU that does Open GL and 1080p30 H.264 decode, and a DSP but there's currently not enough information known to access that yet.

16 GPIO at 3v3, I2C and SPI interfaces will come in handy, it also has stereo audio out. I wonder if it would also have stereo audio in? That could make a very small interface to something like a SoftRock. They also talk about being able to interface to a cheap LCD module for portable operation. Otherwise, it looks like HDMI output.

v---Click on the sbc label to see my other single-board computer posts.

Thursday, September 8, 2011

"High-Speed" data and digital voice

It's a sham that faster digital modes haven't really caught on. I've read about 56k packet in the past. Most radios today support 9600 baud packet, if you can find the discontinued equipment that support those speeds. What does this have to do with digital voice?

Codec2 can squeeze voice into 2550bit/s AMBE can do voice in 2400bit/s and MELP can do it in 2000bit/s. D-Star does a continuous bitstream at 4800baud with 2400 for AMBE voice and 1200 for FEC(Forward Error Correction) (And the voice frames are transmitted blank if you're doing data only, FEC doesn't cover data and you really only get 751bit/s data, I'm not a fan of the protocol)

If someone built a system with Codec2, some FEC and a packetized modem at 9600 baud (or, better 19.2k for the overhead). I'm betting we could have a single-channel digital voice digipeater. I think you'd have to be careful not to use 50% of the channel on each side just because of overhead from headers and the like. It'd be like 802.11, I tx some time, you tx some time, I tx some time, etc. 1 frequency digital repeater. No duplexer cans.

In fact, if the data speed was fast enough we could probably do multiple logical channels with simultaneous users on the same frequency.

More to come.

Monday, September 5, 2011

D-star, P25, other AMBE/IMBE modes

For some reason people are going around saying that "the DSP chip in D-Star, etc radios is really no different than having a DSP in modern HF radios. People don't suddenly refuse the operate their HF radio because they can't see what the DSP is doing."

This statement is a prime example of wrong thinking. What's worse is the same people explain to me that the only difference is the HF radios use the DSP for "IF-level modulation and detection" while the chips in D-Star are just vocoders.

Okay, what is a vocoder? (I am playing stupid here for the benefit for people who really don't know) defines it as:
vocoder (play /ˈvkdər/, short for voice encoder) is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder. The decoder applies these (amplitude) control signals to corresponding filters in the (re)synthesizer.
I don't understand the math behind it. Basically, instead of digitizing the speech and sending it directly over.. the vocoder system renders it into a series of much smaller operations that can be done on the other side to recreate the speech.

This quote from backs this up:
vocoder works by analyzing speech and encoding it as phonemes and other higher-level information, rather than as a continuous waveform. It can thus compress speech into substantially less bandwidth than a waveform codec. Vocoders are generally less intelligible than codecs. They reproduce an evocation of the orginal voice, rather than the actual voice, but sophisticated vocoders like AMBE do so well enough that - except at the lowest bandwidths - the speaker's identity is immediately and easily recognizable. 
The problem with that is certain operations can be patented which will make your vocoder unable to be reproduced legally by anyone other than yourself.

Dave Rowe writes on his website:
Proprietary codecs typically have small, novel parts of the algorithm protected by patents. However proprietary codecs also rely heavily on large bodies of public domain work. The patents cover perhaps 5% of the codec algorithms. Proprietary codec designers did not invent most of the algorithms they use in their codec. Typically, the patents just cover enough to make designing an interoperable codec very difficult. These also tend to be the parts that make their codecs sound good.
So, no one can make a codec that will be compatible with DVSI's codecs, but it is possible to make a codec that works just as good. Codec2 is such a project. It sounds pretty good to me right now, but it is just alpha software at the moment.

The only company that can make chips that are compatible with the vocoder in D-Star, P25 and other radios that use AMBE or IMBE is DVSI. It's true that DVSI just provides the programming on the chips and they are DSP chips from TI. You might even find the same model DSP chip in your HF radio. The problem is to communicate by D-Star you have to have a chip from DVSI in both sides of the conversation.

On the other hand, anyone with a homebrew radio that can do modulation in CW/SSB/AM or FM can communicate with any Gee-Whiz HF radio with a DSP inside of it just fine.

Anyone who says that the DSP in a D-Star radio and a DSP in an HF radio is equivalent is acting in a dishonest manner.

As soon as someone makes a legal source code available that I can load onto a fresh DSP from TI or any other DSP company, build into a radio and communicate with D-Star radios, then I'll stop complaining about the chip inside of them. While DVSI is the only source in the world for said chips, then I'm not going to shut up about it.