| Posted By
bubis
on 2018-09-19
08:27:48
|  MP3 player for Commodore Plus/4.
No, not joking!
My old friend Zsolt Kozma (Chizman) did it, obviously by using a special hardware he built himself.
The sound is coming out of the TED and sounds very cool! Zsolt experimented a lot and measured 45 distinct (although sometimes very close) levels on the TED chip's SNO leg, so his digi is 5.5 bits in theory. (This is not completely new of course, others did similar experiments before.)
Please check out this video, don't miss the part from 07:02!
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Posted By
Luca
on 2018-09-19
08:38:34
 | Re: MP3 player for Commodore Plus/4.
Ooh come on! Now I wanna buy a series of this in order to be ready for Xmas presents! :o
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Posted By
Csabo
on 2018-09-19
09:01:11
| Re: MP3 player for Commodore Plus/4.
Very cool stuff!
I was most excited about seeing what value table he uses - how is it different from TLC's (see here). Seems very similar, but if TLC's values are to be believed, $21 and $91 does not have an audible difference. The other thing is, the player only uses 32 values at most. There's a 64 value table included, but it is indexed with AND #$2F. Perhaps that's actually a programming error?
Anyway, it would be nice to see Chizman's volume level measurements 
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Posted By
bubis
on 2018-09-19
09:15:04
| Re: MP3 player for Commodore Plus/4.
Csabo, I haven't looked into the code, it's up to Zsolt to answer those questions I think.
I am not sure what constitutes audible difference, but Zsolt measured 5% difference between $21/$91.
I will send you his XL sheet.
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Posted By
Chizman
on 2018-09-19
13:03:00
| Re: MP3 player for Commodore Plus/4.
Hi!
I'd like to say thanx to bubis for helping, and Csabo, who noticed my bug. Yes, the correct value is $3F! I wrote over my Plus/4 FM Radio player routine, but it uses the lower 4 bits (the higher 4 bits need to I2C communication with FM radio module, and 3WC with the RTC), and this bug was hidden.
You can hear this 4 bit playing here: FM radio with RTC
Bubis sent me volume values, I collected with my values. I measured the voltage on TED's pin, next I generated a mid freq, and measured the ACV on audio output (of course loaded, the idle voltage may be fake). These 2 values of measuring were different (2 or 3 values). I used the 2nd values, because we hear that.
I made a shorter video with $3F and the full volume values table:
MP3 player V2.0
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Posted By
MMS
on 2018-09-19
13:32:50
 | Re: MP3 player for Commodore Plus/4.
Yeah, this is awesome! You cannot miss the real TED sound Next time maybe a CD player?
The HQ mode works pretty well, and the music in enjoyable, speech is well understandable, there are bass and hi freq too!
Congrats!
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Posted By
Csabo
on 2018-10-07
09:18:43
| Re: MP3 player for Commodore Plus/4.
Sorry for posting this late, better late than never. Here's the list of values from Chizman's measurements.
Excel file:
[ Excel file ]
Values: (index, $FF11, measured output level)
0 $00 0
1 $11 13
2 $21 22.6
3 $91 23.9
4 $12 33.9
5 $31 34.7
6 $B1 46.1
7 $13 54.6
8 $22 60.8
9 $92 62.1
10 $14 76
11 $32 93
12 $15 97.4
13 $23 99
14 $93 100.3
15 $16 118.5
16 $B2 123.5
17 $24 137.9
18 $94 139.8
19 $17 140
20 $33 151.6
21 $18 157.9
22 $25 177.7
23 $A5 178.1
24 $95 179.5
25 $B3 201.8
26 $34 212.8
27 $26 217.4
28 $A6 217.8
29 $96 219.3
30 $27 258
31 $A7 258.2
32 $97 259.7
33 $35 274.4
34 $B4 284.6
35 $28 293
36 $A8 293.1
37 $98 293.8
38 $36 337.2
39 $B5 368
40 $37 401.8
41 $B6 458
42 $38 463
43 $B7 549
44 $B8 631
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