Do mean to say to use a 1k resistor from just the ADC's data out pin to the prop's I/O. Why would you want to use a 1k resistor for the ADC's clock, chip select, and data in pin? I thought the MCP3208 was a 5V device. I just wanted to know if the propeller's output (3.3V) would register as a high on the MCP3208's input pins.
If you take a look into the datasheet you can see that the MCP3208 Vdd can range from 2.7V to 5.5V
I tested the MCP3208 on my PPDB supplied with 3.3V working perfectly.
And supplied by 5V and accidently even connected DataOut WITHOUT a current-limiting resistor worked too.
Back on 3.3V the same prop-pins are still working. (congrats Chip Gracey the propeller is really robust)
But you have to consider that the REFERENCE-voltage should not exceed Vdd. This means if you want
to supply the MCP3208 with 3.3V the max-reference-voltage is limited to 3.3V too.
By the way if you measure lower voltages and these voltages CANNOT exceed f.e. 1V
you can use a 1V-reference-voltage to gain more resolution.
The max-voltage-limit to the analog inputs is Vref.
Just because the Vdd can range from 2.7V to 5.5V doesn't mean that is the logic threshold voltage. I actually just found that the lowest voltage that the MCP3208 accepts as a high is 0.7*Vdd. If I supply the MCP3208 with 5V, that means 3.5V is the lowest digital high voltage. So since the prop puts out 3.3V, the MCP3208 thinks its serial pins are always low regardless of the state of the prop's I/O
If you need to measure higher voltages, use a voltage divider (2 resistors) to get the voltage in range.
luckyshooter353 said...
Will the propeller's 3.3V I/O pins work with Microchip's MCP3208 ADC?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ www.mikronauts.com Please use mikronauts _at_ gmail _dot_ com to contact me off-forum, my PM is almost totally full Morpheusdual Prop SBC w/ 512KB kit $119.95, Mem+2MB memory IO board kit $89.95, both kits $189.95 Propteus and Proteus for Propeller prototyping 6.250MHz custom Crystals run Propellers at 100MHz Las - Large model assembler for the Propeller Largos - a feature full nano operating system for the Propeller
Yes, I guess that would work, even though I don't have 1% tolerance resistors. I could probably measure both resistors with a multimeter and then program the values in.
I run the MCP3208 with 5V supply and 5V ref voltage all the time. It works perfectly and never has a problem. The 3.3V from the prop drives the clk, din and cs with no problem and the output from the dout works fine to the prop. I connect din and dout at the chip and run them thru a 1K resistor to the Prop pin. Works great.
Here's a schematic with a typical ADC circuit using 5V for source and reference. Also includes USB, SD card etc. I've been using it for a while with no problems.
I use the driver called MCP3208_fast.spin from the OBX.
I'm using the MCP32008 and MCP3204 with 5v VCC and 4.096v reference with the Propeller and it works fine. No problems with any of the signals between the prop and the ADC.
Lucky
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I tested the MCP3208 on my PPDB supplied with 3.3V working perfectly.
And supplied by 5V and accidently even connected DataOut WITHOUT a current-limiting resistor worked too.
Back on 3.3V the same prop-pins are still working. (congrats Chip Gracey the propeller is really robust)
But you have to consider that the REFERENCE-voltage should not exceed Vdd. This means if you want
to supply the MCP3208 with 3.3V the max-reference-voltage is limited to 3.3V too.
By the way if you measure lower voltages and these voltages CANNOT exceed f.e. 1V
you can use a 1V-reference-voltage to gain more resolution.
The max-voltage-limit to the analog inputs is Vref.
best regards
Stefan
If you need to measure higher voltages, use a voltage divider (2 resistors) to get the voltage in range.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
www.mikronauts.com Please use mikronauts _at_ gmail _dot_ com to contact me off-forum, my PM is almost totally full
Morpheusdual Prop SBC w/ 512KB kit $119.95, Mem+2MB memory IO board kit $89.95, both kits $189.95
Propteus and Proteus for Propeller prototyping 6.250MHz custom Crystals run Propellers at 100MHz
Las - Large model assembler for the Propeller Largos - a feature full nano operating system for the Propeller
Thank you.
Several good drivers in the object exchange.
Jim
I use the driver called MCP3208_fast.spin from the OBX.
Jim