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Forum Index : Microcontroller and PC projects : DAC recommendations
| Author | Message | ||||
| jovian Regular Member  Joined: 16/04/2017 Location: AustraliaPosts: 62 |
Hi all I'm building a touchscreen based MP3 (or WAV) sheduler, I've successfully propotyped it with the MCP4822 DAC, it works but it sounds too poorly for my needs. Additionally, there is a approx 1V DC offset which produces an almighty thump whenever the PLAY WAV command is issued or when it reaches the end of the file. I tried a DYSV5W board which sounds good but behaves randomly with its SD card file handling over UART and is therefore deemed way too unreliable for my application. Can anyone recommend a 16 bit SPI DAC, good for audio, pref in an inline package? Thanks J |
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| matherp Guru  Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
Are you using MMbasic or building from scratch? If MMbasic the VS1053 is fully supported, will play MP3 etc. See here |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Hi Jovian, The almighty thump with the MCP4822 is something that should be solved by the output circuit, add a capacitor and resistor (or volume potmeter). I do not have a MCP4822 board, so I cannot validate. The almighty thump is result of a single (3.3V) power supply. When it only occurs at startup, you may be able to mute the output until the thump has passed. When it occurs between songs, there may be a fix possible in software, forcing the DAC to mid position in absence of music. Volhout Edited 2024-06-19 17:26 by Volhout PicomiteVGA PETSCII ROBOTS |
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| jovian Regular Member Joined: 16/04/2017 Location: AustraliaPosts: 62 |
Thanks for your thoughts on this. I made an MP3 of silence to test whether it was a a playback glitch and the thump in and out remained. 1.06VDC measured on the DAC output pin, filtering with caps removed it. But it could not remove the transition (which I understand is a transient ac state). The transition seems to be caused at startup and shutdown of the DAC itself. from the datasheet: "Each DAC channel can be operated in Active or Shutdown mode individually by setting the Configuration register bits. In Shutdown mode, most of the internal circuits in the shutdown channel are turned off for power savings and the output amplifier is configured to present a known high resistance output load" I used a spare pin to engage a transistor that briefly pulls the post-filter output to ground. That clears the startup transient, however there is no simple way to time it for the closing spike, as unfortunately that happens before the WAV end interrupt is sent. An option to set Active or Shutdown mode in mmbasic would be fantastic. All that aside, I deemed the 12bit sound of this DAC too lofi for my needs anyway and have purchased a couple of MAX5216 evaluation boards instead, which have a 16bit DAC in an experimenter board format. Hopefully they will not behave the same way. |
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| jovian Regular Member Joined: 16/04/2017 Location: AustraliaPosts: 62 |
This is gold, thank you again Peter. Do you know off hand if this board will work too? I would like to use the VS1053 SD card to save a bunch of internal tones, and have the SD card on the PICO res touch available to the user...  Thanks J |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
If the two SD sockets are on the same SPI bus use a DOUT pin and some logic to switch the CS line from one to the other. |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
That VS1053 is supported for audio output by MMBasic but it requires a SPI of its own. I'm pretty sure that you can't enable both the uSD card and the VS1053 on the same SPI channel. The audio inputs are not supported. It sounds rather nice to my ancient and non-hifi calibrated ears. :) . Edited 2024-06-20 17:07 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| jovian Regular Member Joined: 16/04/2017 Location: AustraliaPosts: 62 |
Thank you Phil |
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| jovian Regular Member Joined: 16/04/2017 Location: AustraliaPosts: 62 |
Yes I'm happy if the inbuilt SD card is not accessible as it will contain ROM sounds. I'll buy a couple and try them out. Thanks for the help. |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Hi, I am not sure the module gives access to the module's SDcard lines. The chip may have full control over these lines. Especially when you can also use it to "record" audio. Also, I am not sure if the picomite can handle "user switched" control of 2 SD cards on the same SPI bus (or different SPI busses). Volhout Edited 2024-06-20 17:14 by Volhout PicomiteVGA PETSCII ROBOTS |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Both sockets will appear as Drive B: so it is up to the user to know which is which and not to switch while the bus is active. Selecting Drive A: before switching B: sockets should prevent MMBasic getting confused. A dummy file on each card with a file name that identifies it would help. Eg:- AA_SDcard_01.txt AA_SDcard_02.txt AA_SDcard_03.txt Starting with AA puts it at the top of "files". It could even be a toggle switch instead of logic. Edited 2024-06-20 18:10 by phil99 |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
SDcards have to be initialised to put them into SPI mode. This happens once each time after a card is inserted when it is first used. A heartbeat then checks the card is still functioning every second or so. This allows insertion and removal without a CD pin. The initialisation uses a particular sequence where the SPI clock is pulsed WITHOUT CS selected. It is very unlikely that two SD cards on the same SPI channel can be made to work with the MMbasic firmware as written. As Mixtel90 notes, the VS1053 uses a dedicated SPI bus and MMBasic CANNOT use an SDcard that shares that bus |
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| jovian Regular Member Joined: 16/04/2017 Location: AustraliaPosts: 62 |
Hi all The making-the-pico-play-audio saga is ongoing. I've purchased a few VS1053's and found them to be good sound-wise. However, the problem I'm finding is that the PLAY WAV command outputs an audible thump, thankfully not full scale, followed by silence and hanging up the program for 3.9 secs, until it eventually begins playing the track and continuing with the program. > autosave timer=0 ?timer play wav "b:/music/21 babylon" ?timer Saved 62 bytes > run 0.055 3964.454 Can anyone tell me if this is to be expected? Is there any way around it? Thanks Jo |
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