We are working on a project based on Vehicle tracking system.In one of our module we are using audio(voice) for Public transport system.As if for now we are using filters and a power amplifer We are not able to get good quality audio output with this setup.
Item used: Lpc2132 with MMC card interface ,High pass filter+ Low pass filter+ Audio Amplifier+ Speaker
Requirement:
Good Voice quality annoucement system for Public transport System
Are you trying to use PWM to play the audio, or a DAC? How are you recording the audio, bit rate and depth?
martin
s
I am using PWM ,.raw format little indian 16 bit 8khz<
How? What's wrong with the quality? (Frequency response/THD distortion/Noise/Effective rms power)
Why do you need these filters?
Are your amplifier and speaker suitable for "good voice quality" ?
Is your clock crystal stable enough for "good voice quality" ?
-- Gemaakt met Opera's revolutionaire e-mailprogramma: http://www.opera.com/mail/
With PWM at 32kHz carrier and 8bit quantization, you can get a "telephone line" quality speech. It would be even better if you apply the preemphasis and the noise shaping to the recorded signal. You can gain somewhat more quality if you combine several PWM channels. However if you need the "music" quality audio, you should use an external DAC.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
As
What about DAC codec ?? It needs I2S interface which is not available with LPC21XX. If anyone know how to convert SSP from microcontroller controller to I2S format in software.
I can do that for you, however this is going to be business.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
Hi!
Use LPC2141-LPC2148 instead (have USB, RTC...), possibly cheaper than LPC2132, and is much faster (interleaved flash...):
LPC2141, LPC2142, LPC2144, LPC2146, and LPC2148 device highlight:
LPC2148:
LPC2141:
Example: MP3/AAC player decoded in the ARM processor:
ARM7 LPC2148 mini board:
/Glenn
What about DAC codec ?? It needs I2S interface which is not available with LPC21XX. If anyone know how to convert SSP from microcontroller controller to I2S format in software.
==> There are plenty of controllers out there with I2S. The AVR32 based UC3A3 has SD-Card I/F, High speed USB, and I2S (as well as ADC/DAC) Should be considerably faster than the LPC as well.
If you insist on ARM cores, then the AT91SAM7A3 has SD-Card interface and I2S interface (SSC).
-- Best Regards, Ulf Samuelsson This is intended to be my personal opinion which may, or may not be shared by my employer Atmel Nordic AB
snipped-for-privacy@v15g2000hsa.googlegroups.com...
f------------ > Its not possiable to change the controller ,I want to know how can i convert SPI1 mode to I2S ,give me the code
meddelandetnews: snipped-for-privacy@v15g2000hsa.googlegroups.com...
------------ > Its not possiable to change the controller ,I want to know how can i convert SPI1 mode to I2S ,give me the code
You need to use a timer which generates the frame sync. This is clocked from the SPI clock. The SPI needs to transmit continuously, or you will have problem. If that is not possible with the SPI block because of internal delays on the SPI clock, then you need to run the SPI in slave mode and generate the SPI clock from another timer.
If you do not have free timer resources, apply for a new job.
While waiting for a new job to appear, please write: "Why are we so stupid that we selected the wrong controller." on the blackboard 100 times.
-- Best Regards, Ulf Samuelsson This is intended to be my personal opinion which may, or may not be shared by my employer Atmel Nordic AB
Give me $700 bln.
VLV
SSP is the coding/decoding format and I2S is the transfer protocol, right? Let me re-phase it, can you convert MP3 into USB?
I'll do it two times faster for half the price!
-- Gemaakt met Opera's revolutionaire e-mailprogramma: http://www.opera.com/mail/
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.