GenBoard/UnderDevelopment/AnalogInputs

While there are many analog inputs (that can also be used for GenBoard/UnderDevelopment/DigitalInputs of coruse), the pinout has not been standardized yet.

proposal for extra ADC input channels

EC18 beware that these inputs are unbuffered and unfiltered, care must be taken to avoid damage to the MCP3208.

DSUB9 male on endplate.

Unfortunately both genders are used: DSUB9 female used for RS232 and DSUB9 male used for LCD. When an ECM has DSUB9 male for both LCD and extra inputs, care is needed at hookup.

The internal HW

The midopa provides 3 nice features:

Values for different amplification:


MCP3208 input load

When using v3.x in an industrial application ( stimulator and tester for a manufactured circuit), we applied external 10k and BAV99 diode protection (quite standard values) to protect the mcp3208 from voltages higher than 5V (or lower than 0). This is not needed when it can be guaranteed by other means that input will only get 0..5V: not an issue when used for pushbutton / switch, we use without extra protection than.

We found that 10nF caps are needed on the mcp3208 inputs for exact measurement when 10 kOhm protection is used: without cap, the internal sampling cap loads the input (likely towards GND) too heavily (impossible to measure with DVM as sampling takes _very_ short time !). With 2MHz SPI clock 4V input could only charge the sampling to 3.3V (this we measured; 500ns time constant is appr 50pF * 10kOhm; not sure if the mcp3208 datasheet specifies so high sampling cap, but PIC microcontrolles taught us in the the past that with microchip we must be careful with datasheet anyway). This could be handled in software with lower SPI clock, but the cap is a good idea in this case (makes the protection circuit 3 components, not 2).