FreeCalypso > hg > fc-small-hw
comparison bb2fc/README @ 0:0f9bdd60ce50
fc-small-hw separated from old freecalypso-schem repo
| author | Mychaela Falconia <falcon@freecalypso.org> |
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| date | Mon, 21 Oct 2019 00:53:38 +0000 |
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| children |
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| -1:000000000000 | 0:0f9bdd60ce50 |
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| 1 The little board to be built in this project is an adapter for connecting an | |
| 2 OMAP BeagleBoard-xM to a FreeCalypso device, specifically connecting Calypso's | |
| 3 MCSI to OMAP's McBSP (primary objective) and also connecting a 4-wire UART | |
| 4 (data + hw flow control) between the two devices - BB expansion interface | |
| 5 provides such a UART, and it costs us very little extra effort to connect it | |
| 6 along with MCSI. | |
| 7 | |
| 8 The present adapter will plug into the expansion header on the bottom side of | |
| 9 the BeagleBoard, implement logic voltage level translation between OMAP's 1.8 V | |
| 10 and Calypso's 2.8 V using the 1.8 V and 5 V power supplies provided by the | |
| 11 BeagleBoard, and bring 2.8 V UART and MCSI interfaces out on headers, intended | |
| 12 to be connected to a FreeCalypso board with jumper wires. | |
| 13 | |
| 14 The logic voltage level translation function will be accomplished using two | |
| 15 74AVC4T774PW ICs, one for the UART and one for MCSI. As a somewhat arbitrary | |
| 16 pick made for greater ease of PCB layout, the A side of each translating | |
| 17 transceiver IC will be the 2.8 V side and the B side will be the 1.8 V side. | |
| 18 Each of the 4 1-bit channels in the 74AVC4T774PW has its own direction control | |
| 19 pin, allowing us to neatly use one of these ICs for each 4-wire interface | |
| 20 despite mixed signal directions. MCSI_CLK and MCSI_FSYNCH are assumed to be | |
| 21 outputs from the Calypso like they are when driven by the DSP ROM code in the | |
| 22 silicon, and they will be voltage-translated in the Calypso to OMAP direction; | |
| 23 the other direction is NOT supported. |