FreeCalypso > hg > fc-small-hw
view bb2fc/README @ 47:ba1450b0c956
duart28c MCL: new components added
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Wed, 29 Jul 2020 07:21:04 +0000 |
parents | 0f9bdd60ce50 |
children |
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The little board to be built in this project is an adapter for connecting an OMAP BeagleBoard-xM to a FreeCalypso device, specifically connecting Calypso's MCSI to OMAP's McBSP (primary objective) and also connecting a 4-wire UART (data + hw flow control) between the two devices - BB expansion interface provides such a UART, and it costs us very little extra effort to connect it along with MCSI. The present adapter will plug into the expansion header on the bottom side of the BeagleBoard, implement logic voltage level translation between OMAP's 1.8 V and Calypso's 2.8 V using the 1.8 V and 5 V power supplies provided by the BeagleBoard, and bring 2.8 V UART and MCSI interfaces out on headers, intended to be connected to a FreeCalypso board with jumper wires. The logic voltage level translation function will be accomplished using two 74AVC4T774PW ICs, one for the UART and one for MCSI. As a somewhat arbitrary pick made for greater ease of PCB layout, the A side of each translating transceiver IC will be the 2.8 V side and the B side will be the 1.8 V side. Each of the 4 1-bit channels in the 74AVC4T774PW has its own direction control pin, allowing us to neatly use one of these ICs for each 4-wire interface despite mixed signal directions. MCSI_CLK and MCSI_FSYNCH are assumed to be outputs from the Calypso like they are when driven by the DSP ROM code in the silicon, and they will be voltage-translated in the Calypso to OMAP direction; the other direction is NOT supported.