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I have some analog devices like LDR, temperature sensors, and other sensors and I want to use the readings of these sensors in my raspberry pi B+ , for that I need an ADC , to convert the analog signals to digital and then transmit them to the rpi. I've searched about it and got this IC name - MCP3008 , which is an ADC with SPI interface, so I would require the MCP3008 IC with the SPI cable. the problem is that, here in kolkata I cannot find any local electronic store that has this IC in their stock. I have to buy it from online stores like mouser.com or digikey.com, but they are too costly, nearly 42$ for just shipping 1 piece.

  1. Is there any direct cheap alternative of MCP3008 which is widely available?
  2. Is there any alternative circuit design that I can do without MCP3008 ?
  • Have you tried eBay? – joan Feb 28 '15 at 11:52
  • Or a domestic supplier? The shipping is probably much cheaper (those sites look to be the equivalent of < $5). I bet you any retailer will mail you whatever you want if you are willing to gamble on paying up front. – goldilocks Feb 28 '15 at 14:22
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I'd look on eBay for less expensive sources for ADCs.

If the resolution isn't too important have a look at PCF8591 based modules. They are only 8-bit but have four input channels. They are I2C rather than SPI (the Pi has an I2C bus).

E.g. http://www.ebay.co.uk/itm/321659640327

Please note that many products sold as compatible with Arduinios will also be compatible with the Pi. An important check is that any outputs from the product are, or can be made, 3V3 safe.

The Pi has two I2C buses. One on gpios 0/1 which is reserved for system use, and one on gpios 2/3 which is for general use.

The Pi also has two SPI buses. The main SPI on gpios 7/8/9/10/11 and the auxiliary SPI on gpios 16/17/18/19/20/21. The standard Linux driver only supports the main SPI. My pigpio library supports both.

  • i have also asked if there is any alternate circuitry of doing what I intend to do. Is there any? And , no I dont want to use an arduino. you say that rpi has I2C bus, where? all i see is GPIO ports – shiladitya basu Feb 28 '15 at 12:19
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    That module may be used on an Arduino. It may also be used on a Pi. The MCP3008 is a SPI chip. Where did you plan to connect that? – joan Feb 28 '15 at 12:22
  • PCF8591 is very good and cheap. It has ADC, DAC, and also light sensors. I highly recommend to newbies. – tlfong01 Apr 9 at 11:53

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