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thwill

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Joined: 16/09/2019
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Posted: 01:07pm 02 Apr 2023

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matherp said CPU frequency 48-251MHz - 44100Hz
CPU frequency 252-377MHz - 88200Hz
CPU frequency 378MHz -132300Hz

Does that mean different filters for different CPU speeds ?

Please stop moving the goalposts, or at least only move them when *I* request it

- obviously I'm not (completely) serious.

Best wishes,

Tom

Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

matherp
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Posted: 01:22pm 02 Apr 2023

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Quote Does that mean different filters for different CPU speeds ?

No, it means a low pass filter that works at default speed will be even better at the higher speeds

thwill

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Posted: 02:23pm 02 Apr 2023

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matherp said

Quote Does that mean different filters for different CPU speeds ?

No, it means a low pass filter that works at default speed will be even better at the higher speeds

Thanks, that's good.

I think I may have misunderstood your post by looking at the pictures rather than reading the text. Does this just support the 12-bit external DAC in that IC family?

Best wishes,

Tom

Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

matherp
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Posted: 02:38pm 02 Apr 2023

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Quote Does this just support the 12-bit external DAC in that IC family?

You can use the 4822, 4812, or 4802 (12, 10, or 8 bits)

thwill

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Posted: 02:40pm 02 Apr 2023

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matherp said

Quote Does this just support the 12-bit external DAC in that IC family?

You can use the 4822, 4812, or 4802 (12, 10, or 8 bits)

Thank you, I guess I'm not as stupid as I look, the price point of the latter may be Ok for the Tomboy.

Best wishes,

Tom

Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

Sasquatch

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Posted: 02:47pm 02 Apr 2023

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This new DAC option is really interesting. I note from the MCP4822 data sheet that the LDAC pin can be tied low. This will cause the DACs to update as soon as the CS pin goes high. For audio applications, precise synchronization of the channels is probably not important. If the LDAC pin could be made optional it would save an I/O pin in most applications.

Quote 3.5 Latch DAC Input (LDAC)
LDAC (latch DAC synchronization input) pin is used to
transfer the input latch registers to their corresponding
DAC registers (output latches, V OUT ). When this pin is
low, both VOUTA and VOUTB are updated at the same
time with their input register contents. This pin can be
tied to low (V SS) if the V OUT update is desired at the
rising edge of the CS pin. This pin can be driven by an
external control device such as an MCU I/O pin

-Carl

Mixtel90

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Posted: 03:01pm 02 Apr 2023

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The 4802 is a lot cheaper - and Bitsbox stock it. Good for experimenting with.

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

matherp
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Posted: 03:29pm 02 Apr 2023

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Quote If the LDAC pin could be made optional it would save an I/O pin in most applications.

It can't otherwise you can't update the second channel until the first has settled and we can't wait around in an interrupt for c5uS @ 132300 interrupts per second. I tried that first.

Tomorrow I will add the capability of adding any user defined waveform to the output.

Create a pattern as 4096 16-bit short integers in the range 0-4095 (100-3900 recommended) in a 1024 element integer array using the memory pack command
Execute PLAY LOAD array%()
Generate the sound with PLAY SOUND chan, L/R/B, U, frequency [,vol]
Edited 2023-04-03 01:39 by matherp

Pluto
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Posted: 04:04pm 02 Apr 2023

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I have a few MCP4922. It needs an external Vref. Do you think that will work?
The only difference in the Write command is bit 14:
-MCP4922 VREF Input Buffer Control bit, 1= Buffered, 0 = Unbuffered.
-MCP4822 bit 14 is "Don’t Care".

If the firmware sets bit 14 to 1 it will not influence the original MCP4822, but will enable 4922 to use the Vref buffer.

Would Vref buffer on or off have any practical influence?

/Pluto

matherp
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Posted: 05:19pm 02 Apr 2023

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Bit 14 is set to 1

Pluto
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Posted: 05:45pm 02 Apr 2023

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/pluto

vegipete

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Posted: 06:54pm 02 Apr 2023

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I notice the RBOX command draws slightly funny if the box is partially off the screen. The straight line section of the box that should be invisible off the edge of the screen is drawn on the edge of the screen. The rounded part is not drawn.
For example, rbox -15,-15,60,60
(PicoMite b32, LCD screen. The CMM2 doesn't do this.)

Visit Vegipete's *Mite Library for cool programs.

Hans

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Posted: 08:02pm 02 Apr 2023

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@matherp

Will the I2C keyboard programming work with any I2C keyboard or is it specific to the one you presented in this thread?

Thanks,

Hans …

matherp
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Posted: 09:37pm 02 Apr 2023

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Quote Will the I2C keyboard programming work with any I2C keyboard or is it specific to the one you presented in this thread?

Specific, but if you know of another then I could consider adding it if the I/F is similar

JanVolk
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Joined: 28/01/2023
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Posted: 10:08pm 02 Apr 2023

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Have a look at M5Stack keyboard?

I don't know anything about it yet, but this might be a nice starter I2C keyboard?

https://www.tinytronics.nl/shop/nl

There they have 3 models for a nice hobby price?

M5Stack CardKB HAT 6.50 Euro
M5Stack CardKB V1.1 Unit 11.00 Euro
M5Stack CardKB Unit 6.50 Euro

Jan

Turbo46

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Posted: 12:09am 03 Apr 2023

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Quote b33/b3 also changes the frequency used for PWM and SPI output for audio as follows

CPU frequency 48-251MHz - 44100Hz
CPU frequency 252-377MHz - 88200Hz
CPU frequency 378MHz -132300Hz

I wonder how that will suit Volhout's filter using the inductor? It is tuned fairly closely to 44.1kHz and, looking at the response curve:

It may not have the same effectiveness at the higher frequencies?

But I believe that that particular curve was simulated without any effective series resistance (ESR) in the inductor. In the real world, they do have ESR which will lessen the depth and widen the breadth of the notch so...

Bill

Keep safe. Live long and prosper.

Hans

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Posted: 12:23am 03 Apr 2023

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matherp said

Quote Will the I2C keyboard programming work with any I2C keyboard or is it specific to the one you presented in this thread?

Specific, but if you know of another then I could consider adding it if the I/F is similar

I wanted to build one specifically to my needs. Thanks, I may take you up on the offer Peter.

Hans …

mozzie
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Posted: 04:09am 03 Apr 2023

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G'day Peter,
Thankyou again, another item ticked off the wish list before being asked for

as you suggest, the addition of the DAC functionality for most audio applications will greatly simplify the analog circuitry involved.

For my own applications and others where almost direct drive of a speaker is required, can I ask if the following is possible in the Pico hardware, and whether you would consider it for a future build?

This is more suitable for sound effect generators, annunciators, Galvanometer drive (HDD head motors) in moving lights / lasers, TomBoy (tm) products (possibly), but I think the guys doing Sine inverters may be able to use it also.

Output is MONO (or use existing command set to "B" for both)
For -2047 0 2047 output modulation values (example only)
Both outputs LOW with 0 modulation (no carrier)
Output 0 goes positive with 0-100% PWM from 1 to 2047 modulation
Output 1 goes positive with 0-100% PWM from -1 to -2047 modulation

Provides zero current standby and the PWM frequency is not as important, even allows 1 transistor audio output like many cheap toys etc.

This basically turns the PicoMite into a class "D" audio driver.

Once again, just an idea for the wish list. Combined with a PicomiteWEB we could have a Wifi controlled laser lightshow and sound effects generator

Regards,
Lyle.
Edited 2023-04-03 14:18 by mozzie

TassyJim

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Posted: 07:43am 03 Apr 2023

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Library command.

Can we have LIBRARY LIST ALL ?
I am adding Library functions to MMEdit's file manager and it will save me looking for all the PRESS ANY KEY... lines.

A means of DELETEing the library but reserving it as an empty library would make file handling easier. I can always create a one line comment program and LIBRARY SAVE it which works but it would delete any current main program in the process.

Jim

VK7JH
MMedit MMBasic Help

matherp
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Posted: 07:46am 03 Apr 2023

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V5.07.07b34 / WEB V5.07.07b4

https://geoffg.net/Downloads/picomite/PicoMite_Beta.zip

This will be the last beta - release candidate(s) next

Support for user loadable sound profiles
Use PLAY LOAD SOUND array%() to load a sound
array%() must be a 1024 element array loaded with 4096 16-bit sound levels between 0 and 4095
Use PLAY SOUND chan, L/R/B, U, freq to output the loaded sound
Array%() is easily created from a normakl 4096 element array using
MEMORY PACK inarray%(),array%(), 4096, 16

e.g.

Dim a%(4095)
Dim b%(1023)
For i=0 To 1023
c%=calc%(i)
a%(i)=2000+c%
a%(2047-i)=2000+c%
a%(2048+i)=2000-c%
a%(4095-i)=2000-c%
Next
plot
Memory pack a%(),b%(),4096,16
Play load sound b%()
Play sound 1,l,U,400
Play sound 1,r,s,400
Do
Loop
'
Sub plot
For i=1 To MM.HRes-1
Line i-1,MM.VRes-a%((i-1)*4096/MM.HRes)/(3900/MM.VRes), i,MM.VRes-a%(i*4096/MM.HRes)/(3900/MM.VRes)
Next
End Sub
'
Function calc%(i)
x%=128
If i<x% Then
calc%=i*1900/(1024*Sin(Rad(x%/1024*90)))
If i=x%-1 Then o%=calc%
Else
calc%=Sin(Rad(i/1024*90))*(1900-o%)+o%
EndIf
End Function

Sorry about the bad picture

Edited 2023-04-03 17:49 by matherp

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