I am developing a wi fi controller that would utilize imp005 module. I am currently in a schematic phase and have question about Imp005 BlinkUp circuitry. In Hardware design section for Imp005 on the web, there is a simple BlinkUp circuit that uses 2 pins (OPTO_BIAS and OPTO_IN). However, I am not sure which exactly are those pins on imp005 module. If we look at the Imp005 Breakout board schematic, we can see something that looks to me like an oscillator circuit (Free run BlinkUp)… I assume that circuit is only for BlinkUp presentation, not really useful for practical stuff?
And it seems to me that OPTO_IN pin would be A50 (I2S0_SD_IN), but what would be OPTO_BIAS on our module (considering A51/BLINKUP_EN is active low)? Any GPIO that should be driven high (supposed it could provide enough amount of current), or could it be +3V3 power rail?
The 005 design doc is incorrect here and needs revision (it was based on the 003 one). The correct circuit is on the breakout board. It is an oscillator - a free-running ramp ADC, in fact - as the 005 has no on-board ADCs.
You need to implement the breakout board circuit, connected to the same pins that it’s connected to on the breakout board. The BLINKUP_EN (A51) is automatically driven by the system when it is “listening” to the phototransistor; if you wanted to leave this enabled - and drop the transistor - you can do that too with only a small power penalty.
Great, thank you very much for your quick response!
I was also wondering, if we are don’t plan using any low power mode, is 32.768kHz crystal still mandatory? The web says it is, but I see it is DNP on a breakout board?
The honest answer here is that the SoC used in imp005 is so new that we haven’t yet determined whether or not it can work satisfactorily as an imp without the 32k crystal. Until we can determine that, all designs should include it.
Hmm, strange it’s shown as DNP on the breakout as we built with that BOM and they’re definitely all populated. As Peter says, populate this now; depending on your application, you may be able to no-stuff the part later once we’ve identified all the possible repercussions of that.
Great, thanks for notification! I have one more question regarding GPIO. Some of GPIO pins from imp005 datasheet are marked as DNC pins on a Breakout board schematic. Should they still be unconnected or we can use them?
Generally this is because due to other silicon limitations these pins are of limited usefulness, so there is no OS support for them and they are marked DNC.
I am not sure if I got it right (those pins are pinned out on imp005). According to a Breakout board schematic, we shouldn’t use GPIO_1, 11, 13 and 15?
What schematic are you looking at? The imp005 breakout schematic is the correct one, which shows all supported pins. We will be getting a new Murata datasheet which marks other pins as DNC.
Pullups are typically 40k and pulldowns typically 45k.