CC2540 Comparator vs Reset

Hello Patrick,

Sounds like an interesting project.  It would be good if you designed it so that you didn't need a meter, you just had the two probes as a wireless measuring device.  Your iOS device would allow you to change the settings and display the readings.

As for you multimeter, the most annoying part of using mine is the auto shutdown feature.  There isn't a switch to enable/disable it.  If you put the CC2540 to sleep mode 3 then it is no longer connected.  You may want to just have it shut off when the switch is off.  Of course if you have another processor then you can use it to bring the CC2540 out of sleep mode.

You can also just use the CC2540 as the only MCU for the meter.  You can either use software i2c or SPI and connect to an ADC and LCD and still have BLE connectivity.

Thanks,

Hi,

Actually, we already have the meter that you describe, and although it won Test & Measurement World's "Best in Test" award for multimeters in 2012 (beating entries from Fluke, Tek, and Agilent), it was a resounding commercial failure for a variety of reasons. Like you, we thought a WiFi based meter with App display would be great - not so much.

Our current meter project is a more traditional meter with the CC2540 built in. It communicates to a MCU that already does the measurement of voltage, current, frequency, temp, etc. To your point about allowing the meter to turn off when the selector switch is turned off, would this have any adverse effects on the SW state of the CC2540? Our app enables and disables the APO function to allow extended logging to the 2M of on-board memory & measurement.

Our thought is to use the either the Reset_n or comparator function on Pin P0.4 and Pin P0.5 to provide button push from the user to wake from Power Mode 3 or Reset. What are your thoughts on the appropriate choice?

Thanks

Well, it is a pleasure to be communicating with you Patrick.  I like the device,  

The probably reason for its slow take up was that it was launched when very few inexpensive mobile devices and tablets were available.  Also, you should have some kind of accessory for putting your phone/tablet in when working.  

In the field, you are always struggling to find a spot that you can put your multimeter in that allows you to check voltages, see the values and won't cause it to fall down.  You sometimes have to hold the leads on contacts and wait for them to change state.  Plus you have to put it down on live terminals sometimes.

Since you are not using the CC2540 for running any applications then I would go with the reset.  This will ensure that your BLE connection will be automatically started just in case something caused the CC2540 to halt.

Transmitting 2Mb of data with BLE will take a bit of time, but is the only option for iOS if you are not on the MiFi program.  Are you aware of the CC3200 ARM Cortex-M4 with built in WiFi?  This would seem like a closer fit since you already use Wifi in the iDVM.  All the DMM and logging could be handled by this MCU alone.

Thanks,

The pleasure is mine. We have been kicking this problem around internally and sincerely appreciate input from this community of users.

The iDVM uses a ARM Cortex M-3 from another supplier. The C3200 would be a worthy contender if we were starting this project now.

Thanks again!