8 ADC inputs Need Slave Chip
September 7, 2011
It looks like I am going the brain/ multiplexer route here and will make the ultimate line-follow sensor of death. Led's will be off of PWM for brightness control, white/black threasholds will be adjustable and now I have decided that adjustable pull-up resistors would be handy too. I figure that a simple trimmer pot connected to the common of my resistor array would do the trick, but I would not mind some feedback on the issue. I have added a second video with an explaination. Thanks in advance.
I have been plugging away at my line follow sensor and my related I/O expander issue and have hit a bit of an impasse. My original idea of using a digital I/O expander to keep an eye on all 8 sensors has fallen-through and in hindsight, was probably not the way to go in the first place. As it stands now, I have a simple problem of reading 8 IR sensors via ADC without using 8 pins on the main microcontroller. I simply need a support chip to sit on the line follow board itself and communicate with the main brain. Here are my requirements:
- Must speak UART serial or preferably I2c
- Must have a minimum of 6 ADC's preferably 8 --I really want 8
- Must be smaller than a 28-pin dip (a full-size arduino will not fit --I can use a SMD atmega 328 though)
The main options in my mind are an Arduino 328 or a Picaxe 18m2 (or something else). The arduino, even in SMD form, is a little cheaper than the picaxe but only allows for 6 ADC inputs. There are 8 ADC pins on the SMD version, but I have yet to figure out if I can get a hold of them. Whether I can or I can't, I am still going to loose 2 of them if I want to use the I2C lines (my preference).
The next choice is the Picaxe 18m2 which has a ton of ADC's (more than I need) and is only about $.50 more than the Arduino. This so far, seems to be the option I want to use, but alas, the picaxe has no provisions to become a I2C slave. It can actually, but unfortunately only to access it's memory functions (when in I2c slave mode, the picaxe becomes a fancy EEPROM really). This puts me back to using UART serial again which I would prefer not to do.
One more: I cannot use any of the MCP320x chips (which would solve all my problems) as they are SPI and the new Picaxe chips don't speak SPI. Arrggg.
At this point, I open the floor...