Urgent - nrf8001 and AtMega328

RE: Urgent - nrf8001 and AtMega328

Nguyen Hoan Hoang — Sun, 15 Mar 2015 20:36:17 GMT

The short range is likely caused by the PCB layout and component placement. You must not have any traces or planes or any components under the antenna area, even on the other side of the board.

RE: Urgent - nrf8001 and AtMega328

Francois — Sun, 15 Mar 2015 20:29:03 GMT

So we manage to connect to the BT module. The MISO shifting as indeed the problem. However wireless range is about 10cm (hum...) and we can't make the echo demo code work (TX but no RX). A colleague is on the serial port to understand better.

RE: Urgent - nrf8001 and AtMega328

Nguyen Hoan Hoang — Sun, 15 Mar 2015 15:03:13 GMT

Bypass the transistor. Remove the pullup on 5V. Keep the pullup on the 3V. I think it should work that way.

RE: Urgent - nrf8001 and AtMega328

Francois — Sun, 15 Mar 2015 13:11:11 GMT

If I want to keep current board, any reco on which component to use to do the same in SOT23? I'm afraid that removing the pull-up for the nrf8001 will work but SC card will not work anymore. What do you think?

See forum.arduino.cc/index.php

RE: Urgent - nrf8001 and AtMega328

Francois — Sun, 15 Mar 2015 12:45:38 GMT

Yes.

I will connect it directly.

See this: github.com/.../5 and this github.com/.../Adafruit-Bluefruit-LE-nRF8001-PCB

MISO isnt shifted so I will try it this way.

Thanks again. Will keep you informed.

RE: Urgent - nrf8001 and AtMega328

Nguyen Hoan Hoang — Sun, 15 Mar 2015 12:35:48 GMT

Level shifting MISO is not the problem. In fact it is better to level shift it. What I suspect is the transistor level shifter design you are using. That is why I suggested to check the SD card. If you can access the SD card, that would prove the MISO works. I would also suggest using this chip SN74AVCH4T245DGVR. It is more flexible to use in your design as it allows you to select the direction.

RE: Urgent - nrf8001 and AtMega328

Francois — Sun, 15 Mar 2015 11:30:20 GMT

Hi, I think you might be right. After looking at several other BT modules, MISO isn't shifted. Will try it today... This thing is killing me :-)

RE: Urgent - nrf8001 and AtMega328

Francois — Sun, 15 Mar 2015 11:29:20 GMT

We are on it! Thanks we will keep you updated.

RE: Urgent - nrf8001 and AtMega328

Michel — Mon, 09 Mar 2015 13:44:51 GMT

Okay, I misunderstood your comment and therefor my reference to the 8MHz is not valid. I do agree it's a bad idea to overclock your product. Enough off topic. You still have the issue with the nRF8001. Did you get the SD card working? Are the signals converted correctly? Maybe freeze your code and start with some dedicated code for just checking your layout. Toggle all the outputs, read the inputs and find an example for SPI with the ATMEGA328. Get back to the basics.

RE: Urgent - nrf8001 and AtMega328

Francois — Mon, 09 Mar 2015 13:38:40 GMT

Thanks. Will do. John's answer help me found a local guy here who might help me... Will keep you informed. Thank you very much for your support.

RE: Urgent - nrf8001 and AtMega328

Nguyen Hoan Hoang — Mon, 09 Mar 2015 13:34:48 GMT

RDYN may work. What you need to do is to make sure the SPI interface works. You have the SD card connected to the same SPI. It does not use the RDYN pin. So with that you can verify the SPI work properly or not. It would also isolate the RDYN pin. The SD card is easier to validate.

RE: Urgent - nrf8001 and AtMega328

JohnBrown — Mon, 09 Mar 2015 12:55:54 GMT

My point was that, if you are a hobbyist, there is little harm in slightly overclocking a single part, provided you can verify that it works OK. If you are in production it is a bad idea. I have no idea what relevance your reference to the 8MHz internal clock has...

RE: Urgent - nrf8001 and AtMega328

Michel — Mon, 09 Mar 2015 12:41:33 GMT

Oh yeah indeed. The maximum clockfrequency is supply dependent. If you application needs 20MHz than indeed the 3.3V is not suitable for you. But this clockfrequency doesn't have anything to do with hobby or commercial projects, but with your own specifications. Arduino is more likely for hobbists than the clockfrequency. Some years ago I used the ATMEGA328 with the internal clock of 8MHz for a commercial product and it worked perfect.

RE: Urgent - nrf8001 and AtMega328

JohnBrown — Mon, 09 Mar 2015 12:17:06 GMT

I believe that 16MHz at 3V3 is slightly out of spec. OK for a hobby project, perhaps, but I wouldn't want to run outside the spec for a commercial project.

RE: Urgent - nrf8001 and AtMega328

Michel — Mon, 09 Mar 2015 12:11:08 GMT

Why are you running the ATMEGA328 on 5V. It will accept 3.3V as well. Select the PD1(TxD) indeed for bit-bang serial Transmit (Uart) will give you a great debug posibility.

RE: Urgent - nrf8001 and AtMega328

Nguyen Hoan Hoang — Mon, 09 Mar 2015 09:55:13 GMT

I would more likely suspect the level shifter on MISO pin via Q3. Does your SD card work ?

RE: Urgent - nrf8001 and AtMega328

JohnBrown — Mon, 09 Mar 2015 09:50:37 GMT

You have an LED output. Add a simple bit-bang serial tx function using the LED pin, hook it up to a FTDI UART-USB module and run a simple terminal program on your PC. You now have debugging. That'll be 50 pence or one euro, please.

RE: Urgent - nrf8001 and AtMega328

Francois — Mon, 09 Mar 2015 08:13:43 GMT

Is it possible I have problems because RDYN is not shifted from 3.3 V to 5 V so AtMega don't receive handshake signal?

Thanks again for your help.

NNH: We didn't try the SD card yet...

Other than that do you believe the pinout would be a problem? RDYN do not need to be shifted?

John: Thanks. As you can see my knowledge around all this is not very "deep". Will share that with the guy who is helping me...