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annotate bb2fc/README @ 77:4c5675c79555

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lunalcd3.pcb: add orientation marker to SW1
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 18 Nov 2021 07:40:13 +0000
parents 0f9bdd60ce50
children
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0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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1 The little board to be built in this project is an adapter for connecting an
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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2 OMAP BeagleBoard-xM to a FreeCalypso device, specifically connecting Calypso's
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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3 MCSI to OMAP's McBSP (primary objective) and also connecting a 4-wire UART
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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4 (data + hw flow control) between the two devices - BB expansion interface
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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5 provides such a UART, and it costs us very little extra effort to connect it
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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6 along with MCSI.
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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7
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
8 The present adapter will plug into the expansion header on the bottom side of
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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9 the BeagleBoard, implement logic voltage level translation between OMAP's 1.8 V
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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10 and Calypso's 2.8 V using the 1.8 V and 5 V power supplies provided by the
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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11 BeagleBoard, and bring 2.8 V UART and MCSI interfaces out on headers, intended
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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12 to be connected to a FreeCalypso board with jumper wires.
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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13
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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14 The logic voltage level translation function will be accomplished using two
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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15 74AVC4T774PW ICs, one for the UART and one for MCSI. As a somewhat arbitrary
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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16 pick made for greater ease of PCB layout, the A side of each translating
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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17 transceiver IC will be the 2.8 V side and the B side will be the 1.8 V side.
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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18 Each of the 4 1-bit channels in the 74AVC4T774PW has its own direction control
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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19 pin, allowing us to neatly use one of these ICs for each 4-wire interface
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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20 despite mixed signal directions. MCSI_CLK and MCSI_FSYNCH are assumed to be
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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21 outputs from the Calypso like they are when driven by the DSP ROM code in the
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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22 silicon, and they will be voltage-translated in the Calypso to OMAP direction;
0f9bdd60ce50 fc-small-hw separated from old freecalypso-schem repo
Mychaela Falconia <falcon@freecalypso.org>
parents:
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23 the other direction is NOT supported.