91 lines
3.3 KiB
Plaintext
91 lines
3.3 KiB
Plaintext
Product summary:
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Dreamcast USB-UART adapter, featuring new durable Dreamcast serial connector.
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Does not contain recycled/scavenged components from any Sega-original product.
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Usable as a COM/tty port with generic software (FTDI VCP drivers required on
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Windows; usable with no configuration on Linux). Custom software is also
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provided for more advanced functionality.
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What can you do with it?
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This product is primarily intended for people interested in developing new
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software for Sega Dreamcast.
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For Dreamcast units with boot ROMs that will load software from CD-R (e.g: VA0,
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VA1).
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Example/suggested use-cases include:
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- copy newly-written software from a PC to Dreamcast RAM for rapid compile/test cycles
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- create dumps of Dreamcast texture memory (framebuffer "screenshots", Holly/emulator development, application debugging)
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- SH4 debugging via GDB
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- serial printf debugging
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- interactive text console via a terminal emulator (minicom/picocom/screen/putty)
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Many other data transfer use-cases are possible, including VMU save backups and
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CD-ROM/GD-ROM backups.
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Features:
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- Capable of sustained data transfer at 1.5 Mbit/s, read and write (the
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maximum configurable speed of the Dreamcast SCIF)
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- Dreamcast global reset, user-controllable via USB (reset the Dreamcast
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without pressing the power button)
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- Two LEDs, user-controllable via USB (by default configured as TX/RX activity LEDs)
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Transfer benchmarks:
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Benchmarks are performed using the `ftdi_transfer` open source transfer program
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on Linux.
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- 50 kbyte @ 0.425±0.001 seconds (idealized time: 0.419 seconds)
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- 1 Mbyte @ 6.666±0.002 seconds (idealized time: 6.711 seconds)
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- 8 Mbyte @ 53.253±0.015 seconds (idealized time: 53.687 seconds)
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- 15 Mbyte @ 99.854±0.026 seconds (idealized time: 100.663 seconds)
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The integrity of the bytes transferred in each transfer are checked and
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verified. Each test is repeated and averaged 10 times.
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The results where the benchmarked speed is faster than the idealized time are
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not a mistake. This occurs because FT232H chip is transmitting at 1573770
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bits/sec, which is 0.721% faster than the Dreamcast's 1562500 bit/s. The SH7091
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manual specifies (receive) speeds within 1% of the configured rate are
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acceptable. Because the SH7091 SCIF performs 16x oversampling of the received
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serial data and resynchronizes on every start bit, this effectively means that
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the SCIF is being "overclocked" by 0.721% when the receive line is driven by a
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FT232H.
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The results where the benchmarked speed is slower than the idealized time is
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because the round trip time of an extra USB transaction is included in the
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benchmark measurement. This extra USB transaction is used to retrieve the CRC32
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checksum of the transmitted data, as computed by the Dreamcast. The extra USB
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transaction is also used to positively affirm the serial transfer is complete
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(and not simply queued in the FT232H transmit buffer). This USB transaction
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latency is relatively constant, and becomes insignificant with larger transfers.
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Technical specifications:
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Dreamcast serial connector:
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- Aluminium shield/shroud (SLM 3d-printed)
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- Aluminium conductive pins (laser-cut sheet metal)
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- Plastic pin-housing (SLA 3d-printed)
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USB UART PCB:
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- FTDI FT232H USB UART
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- 93LC56BT 2kbit configuration EEPROM
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- custom 4-layer PCB
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