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Old 10th September 2007, 09:38 AM   #1
traf is offline traf  United Kingdom
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Question microcontroller programming

Firstly apologies if this is a bit long winded.....

I'm in the process of trying to modify my Musical Fidelity A5 DAB tuner, splitting it into separate DAB tuner (which is a bog-standard Gyrosignal module) and DAC stages (the DAC is rather good and is the same as that used in the A5 CD player).

There is an I2S test input socket on the main circuit board (underneath the standard DAB module) and I have managed to get some good sounds from the DAC stage by taking a 44.1kHz/16bit PCM feed from an old Pioneer DV444 DVD player. When fed a 48kHz/24bit signal from DVD quiet levels are OK, loud ones are very distorted/clipped. This suggests to me that the SRC4193 sample rate converter is programmed to accept only a right justified fixed 16bit word length (if it were left justified, 24bit material would sound OK and simply lose the last LSBs). Nor will it accept an I2S feed (I've tried various sources and all I get is white noise).

I've order a Twisted Pear Audio WM8804 SPDIF receiver board so that I can use the DAC stage for 16bit material derived from an SPDIF input and will use my Meridian 518 to switch between digital sources and as a digital volume control (even with the effects of lost dynamic range it sounds better than my passive preamp).

However, I would eventually like to use the DAC stage for 24bit material, so I would need to either:

a) Replace the SRC4193 sample rate converter with the hardware programmable SRC4192 version.

b) Program a replacement EPROM controller (not sure what sort is fitted) to make the SRC4193 accept up to 24bit left justified material. The EPROM also controls the DSD1792 DAC which makes life a little more complicated.

I'm sure I can come up with the appropriate register map to control both devices, but what I have absolutely no knowledge or experience of is programming the appropriate EPROM.

Can anyone offer any advice - are EPROM programming hardware expensive/difficult to use? Anybody out there offer a service?



cheers
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Old 10th September 2007, 01:19 PM   #2
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If the MF A3.24 is a reliable guide then the A5 probably has a PIC microcontroller running the show.
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Old 10th September 2007, 01:35 PM   #3
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Hi Traf,

Sorry to derail your thread a bit - I am interested to use the Gyrosignal module as IF DSP with my Yamaha tuner as RF front-end. Can you tell me the model number of the Gyrosignal it uses?

You can email me through the email button if it does not cause you too much troubles.


Thanks


Patrick
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Old 10th September 2007, 02:49 PM   #4
traf is offline traf  United Kingdom
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Patrick

Can't email as I'm 'still under moderation'.

It uses the 1120 module - I can't find anything on the web about it but I suspect it is a licensed version of the Radioscape 200 series. If you find a datasheet for it please do let me know. All I've managed to find out are where the FS, Bclk and Data pins are, so I know which ones to remove.

Simon
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Old 11th September 2007, 01:16 AM   #5
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Hi Simon,

Actually, I have the pin out diagram for Gyrosignal's 1120 module from the Teac TR610 FM/DAB tuner service manual. This Teac tuner does not output digitalised FM via SPDIF but it can be done according to the SM.

Please email me patrickkan1@gmail.com . I will send you the Teac SM. I will see if I can get couple 1120 modules from Gyrosignal as I am interested in using their IF DSP and digital out for FM tuner project.


Patrick
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Old 12th September 2007, 09:31 AM   #6
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Hi Simon,

Did you get the schematics sent via email?

Does it help?


Patrick
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Old 12th September 2007, 11:32 AM   #7
traf is offline traf  United Kingdom
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Yes thanks Patrick although I haven't had a chance to review the schematic yet (I'm away from home at the mo). Will let you know how I get on.

I have identified the microcontroller as a PIC16F818 for which it is easy to get a programmer (velleman do one) and spares. The issue now is whether I'll be able to read the existing code or whether the chip has been locked. If the former, changing individual registers will be straightforward. If the latter I'll have to program the thing to control both the SRC4193 and DSD1792. That is bound to be fun!
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Old 12th September 2007, 12:49 PM   #8
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If you read the device, all you'll see is a hex file with few clues as to what does what. It would be much simpler to monitor the chip select pins and SPI/I2C data for the relevant register and alter the associated data accordingly.
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