http://forums.leaflabs.com/topic.php?id=1542 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:08:10 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=1542#post-10152 Mon, 09 Apr 2012 07:18:42 +0000 higwoshy 10152@http://forums.leaflabs.com/ <p>Thanks, I'll give it a go. Off to ebay... </p> http://forums.leaflabs.com/topic.php?id=1542#post-10151 Mon, 09 Apr 2012 06:56:53 +0000 crenn 10151@http://forums.leaflabs.com/ <p>That is correctly, usually you need to pull a CS line low (there might be devices where you need to pull it high) to select the device.</p> <p>Technically it is possible, however some devices will not set their output to high impedance (which is important) when the device is not selected, there are ways around this. You can switch between mode and frequencies between devices, but you need to remember to set it before selecting each device, however having the same mode and frequency makes it easier.</p> <p>It's been a while since I last used the Hardware SPI library, but I do believe that is correct. </p> http://forums.leaflabs.com/topic.php?id=1542#post-10149 Mon, 09 Apr 2012 06:39:54 +0000 higwoshy 10149@http://forums.leaflabs.com/ <p>Hi,</p> <p>I'm thinking of buying a MCP4922 which is a dual 12bit DAC with an SPI interface and not having much experience of SPI apart from using it in various libraries I need a bit of hand holding before I get started.</p> <p>Some simple (hopefully) questions.</p> <p>As far as I can tell the HardwareSPI library doesn't setup the CS pin itself, that needs to be done before calling <code>write</code> - is that correct? </p> <p>Therefore I assume the two SPI lines (MISO/MOSI or SDI/SDO) can be shared between devices? I am currently using SPI_2 for a SD card and SPI_1 for a RF2401 transceiver. If I share the SPI lines between the SD card and the DAC and use a separate CS pin for each device to select will I run into problems, assuming they use the same <code>mode</code> and clock frequency?</p> <p>The 4922 needs a 16bit word sent (4bits control, 12bits data)- will that be a problem with the maple which only sends a byte at a time. I'm assuming I just use the multi-byte <code>write</code> command. Something like the code below should work?</p> <pre><code>uint16 fred = ccccdddddddddddd; // (bits:c=control, d=data) digitalWrite( MCP4922A_CS, HIGH); // or low if it&#39;s _CS... spi.write( (uint8 *) &amp;fred, 2); digitalWrite( MCP4922A_CS, LOW);</code></pre> <p>I just need to know if I'm on more or less the right path before I purchase. </p>