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Cheapest Microcontroller with I2C & UART for industrial

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Aug 23, 2009
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cheapest microcontroller


I'm designing a 3.3V microcontroller based project that need to interact with two chips using UART and I2C. I would like to ask everyone what is the cheapest/smallest microcontroller to use? We plan to make tens of thousands of boards with the chosen microcontroller so I want to ask professional opinion before we decide what to use.

Basically the Microcontroller has to read data from the first chip using UART(3.3V, 19200bps), then write it to the second chip using I2C; The microcontroller then read the processed data from the second chip via I2C and write it to the first chip via UART. The microcontroller need to be the I2C master.

I see there are many 8-bit PIC microcontrollers from Microchip that have hardware based I2C & UART modules. But I heard PICs are not really used in a industrial setting and are used mostly by hobbyists.

I'd be really grateful if anyone can share suggestions on where do I start to decide the best microcontroller to use? it needs to be as small as possible, and due to the large number of PCB boards we will make, price is also a big concern.

Thanks in advance!!!


cheapest and best microcontrollers available

Philips P87LPC762 has both ports and is quite cheap.

PIC controllers are very rugged and I have used them in industrial environment for over a decade.

If you want a really cheap solution, use a software based UART. For example, you can use a cheap microcontroller ($0.4 in qty) at high clock (<1us cycle time) to make a read-only UART at 19200 and write-only I2C.

If you want, I can do the design for you at a small cost.

cheapest microcontrollers


Thanks for the very fast reply. I am definitely interested if you can design it for us. Please PM for your price range.

The NXP microcontroller looks great. Do you know how much it costs if purchased en bulk? I looked on Digikey, the price per 1000 is 1.3USD. Is that a reasonable best price I can get? Is the P87LPC762 a popular part in production?

About the software UART & I2C. The microcontroller needs to both read and write from the UART & I2C. Can the software implementation handle both?

The specs of the I2C chip the microcontroller will talk to indicates that it may perform clock stretching. Would that cause a problem if the I2C master is implemented in software on the Microcontroller?

Thanks a lot again!

uart to i2c

timevision said:
I see there are many 8-bit PIC microcontrollers from Microchip that have hardware based I2C & UART modules.
Microchip has almost 200 8-bit controllers that have a UART and I2C controller, several of which are around $1.00. They have a great on-line selection tool that allows you to pick the features you require and display the matching devices:

timevision said:
But I heard PICs are not really used in a industrial setting and are used mostly by hobbyists.
Microchip is the World's largest manufacturer of 8-bit processors, and cater to the industrial and commercial markets. They don't don't market directly to the hobbyist, nor do they have a support channel for hobbyist. Despite this they are popular among hobbyist because they are readily available (all major parts distributors sell them), they are inexpensive, there's a huge selection of parts (close to 500), there's a lot of compatability between parts, and there's is a lot of "community support" for them. Also, Microchip is one of the most stable electronics manufacturer in the world, having just posted revenue increases of 11% in the last quarter.

When picking a microcontroller there are several things to consider besides the peripherals and the cost:
- Program Memory and RAM size
- Speed
- Temperature Range
- Available package sizes
- Compatability with other devices in the family - Footprints, hardware and software
- Development Tools -Boards, IDE, Assemblers/Compilers, etc.
- Product support - Training, Application Notes, Engineering and Sales Support
- Distribution Channels
- Manufacturer Stability

With the quantities that you are considering, this is an important decision for your business. I'd suggest you contact Microchip and talk to your local Field Application Engineer. They'll help you decide which is the best processor for your project.

If you need design help, I'm a Microchip Authorized Design Partner and can assist you with your hardware and software needs.

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