gbs-c incorrect aspect ratio

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mrchief
Posts: 24
Joined: Wed Jun 25, 2025 2:42 pm

Re: gbs-c incorrect aspect ratio

Post by mrchief »

After reading the main thread, all posts. Found out that the incorrect aspect ratio was intentional. And maxed out fifo 1024 on horizontal was to increase sample rate, if i remember correctly. my gbs-c works only in baud 9600 and i couldn't get wifi to work for connection. need some thoughts if 2640x1125 is even a thing for gbs-c. there are many reasons i don't know about why the preset is like this.

left number is rama 1080p pal preset
Vds_vsync_rst 1125 Vtotal 1125
Vds_hsync_rst 1444 Htotal 2640
Vds_dis_hb_st 1262 Hblank start 2640 or it's 1440?
Vds_dis_hb_sp 260 Hblank stop 2640-1440 = 1200 or it's 2640?
Vds_dis_vb_st 1124 Vblank start 1125
Vds_dis_vb_sp 28 Vblank stop 1125-1080 = 45
Vds_hs_st 8 Hsync start 1440 + 768 = 2208
Vds_hs_sp 48 Hsync stop 2208 + 44 = 2252
Vds_vs_st 1 Vsync start 1080 + 4 = 1084
Vds_vs_sp 6 Vysnc stop 1084 + 36 = 1120
---------------------------------------------------------------------------
no idea how these works, registers for fetch data:
Spoiler
Vds_hb_st [11:0]
0xB4, // s3_4
0xA4, // s3_5
10110100
10100100
010010110100 - 1204

Vds_hb_sp [11:0]
0xA4, // s3_5
0xA, // s3_6
10100100
00001010
000010100100 - 164

Vds_vb_st [10:0]
0x3, // s3_7
0x0, // s3_8
00000011
00000000
00000000011 - 3

Vds_vb_sp [10:0]
0x0, // s3_8
0x1, // s3_9
00000000
00000001
0000001000 - 8

1440+528+240+44+148+240=2640
1080+4+36+5=1125

front porch 528 + 240, sync pulse 44, back porch 148 + 240 = 2640 (240 for 1440 active)
front porch 4, sync pulse 36, back porch 5 = 1125
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