Group Actions
Engagement
  • Author Author: michaelkellett
  • Date Created: Date Created
  • Views 1620 views
  • Likes 3 likes
  • Comments 5 comments
Related
Recommended

ARMP Processor and Display

michaelkellett

15/08/2020

This is still very much work in progress.

 

I've confirmed my primary choice of display, the Riverdi RVT43ALBFWN00, available from Mouser and RS.

It has an SPI interface over a 20 way FPC and uses a Bridgetek controller chip. This is fairly smart and reasonably

well documented chip and very much mitigates the slowness of controlling a hi res display over SPI. It costs about £27.

 

Here's a picture - of the important side !

 

image

 

The plan is that the display will bolt onto the main pcb (on the non component side) and connect via a short flat cable.

 

I've wasted a lot of today trying to get to grips with the Espressif ESP32 WiFi and Bluetooth chip and it's modules. When I first

suggested using this part I mention that there is a lot of community support for it. It's more a case of a lot of community talk about it !

Precious few schematics that inspire confidence.

The best article I found about getting it to work with AT commands was far too scary:- don't use the latest version of the tools, compile the code

again because it won't work if you use the binary, install and hack some kind of boot config tool thing ... and on and on ! How can this thing

possibly claim any kind of certification ?

 

I've used a Microchip module, it only does Bluetooth and it costs twice as much, but you connect it, configure it (without re-designing the tools) and it works.

 

We could use that,  but I'm now thinking of just providing a header with serial port, six uncommitted IO lines and 3.3V power (peak current 1A).

 

If anyone has a certified module in mind, that they have used and can link me to a schematic of it interfaced to micro ( that is known to work),

I could be persuaded.

 

I've got a preliminary processor pin allocation, I end up with about 25 IO pins free, so certainly no need for more than the 100 pin package.

 

 

image

 

I've also completed my battery testing programme.

I bought a pair of claimed to be 7.4V 8.8Ah Sony compatible batteries from Amazon - very cheap at £41

for both batteries and the dual charger. The charger is slow(since it's USB powered but it works OK.

I did 10 successive run down tests and the results are surprisingly good. Not quite up to spec but little sign

of early degradation. One battery has about 4% more capacity than the other -  not  a big deal.

image

 

 

if anyone has any ideas re the BlueTooth.WiFi I'd really like to hear about it.

 

(BTW - I forgot to tag the last blog about the ADC properly.)

 

MK

  • Hello Shabaz,

     

    Digilent publish pin outs for 12 pin UART and SPI PMPODs and I'll comply with them.

    The 3.3 V will be connected to the main 3.3V supply, so capable of as much as 1A (aggregate across all PMODs) at 3.3V.

     

    MK

  • in reply to michaelkellett

    Hi Michael,

     

    Awesome, if that UART PMOD can have ideally 3.3V up to 30mA for VCC then that's perfect for any typical Bluetooth chip like the TI one Frank suggests or the Silicon Labs one. I have already got a footprint for the BGX13P for a different project so I'm halfway there already since it's a trivial board, and it could always be replaced with a different chip in future if desired.

    imageimage

  • RE Bluetooth - Probably not much help but the only one I have used is the TI CC2650 with a MSP432.  Here is a link to the module I used:  https://www.ti.com/tool/BOOSTXL-CC2650MA .  It was easy to get started with the MSP432 and the TI development tools but I didn't stray far from their examples and have never looked at how it would integrate with other microcontrollers.

     

    Frank

  • in reply to shabaz

    I've made the external LCD, Wireless and general expansion ports into PMOD ports using 12 pin connectors.

    This means that there are some ready made things that will connect directly to them.

    Sadly there isn't a spare SPI port, since I'm using all three (one for display, one for FPGA and one for Flash.)

    If the FPGA ends up with enough spare pins it may get a PMOD port of its own.

    The UART PMOD format gives you a 4 wire UART (with RTS and CTS) and 4 general purpose IO signals so

    it would work with the chip yo suggest.

     

    I may have enough pins to bring out an I2C port , and even a CAN port (although I'm not sure if it would be any use to any one.)

     

    MK

  • Hi Michael,

     

    Awesome, that's a good price for a display!

     

    ESP32 guides are quite poor, I always waste half a day trying to recall how to use it, and have never got around to writing some notes.

    The header is a much better idea, otherwise there's a BLE module I tried recently, and reviewed by others, Silabs BGX13P, which is straightforward to use.

    It is BLE only, not Bluetooth 2.0, so the remote end needs code to make it look like a serial port (or for existing PC app connections using serial port replacement, use two devices back-to-back). The only downside is that (without using two of them back-to-back) it primarily only connects to mobile devices (iOS/Android) since that's all the manufacturer has supplied SDK code for. It can connect to a PC (Windows/Mac/Linux) in non-back-to-back configuration but it's non-trivial. Nevertheless, since the main use-case for wireless is likely to be to pull off data or configure from mobile, it could still be a good option, and it doesn't rule out PC, it's just harder. And existing PC apps are still supported out-of-the-box, albeit with another BGX13P for the back-to-back configuration.

    It's also cheaper than ESP32, and easy to use. It doesn't support WiFi, but that doesn't seem a major negative.

     

    The diagram below is from the datasheet, basically the boot pin can be pulled up via 100k resistor to VDD (no need for a jumper), and RESETn pin doesn't need a connection, or can be connected via open-drain to a reset signal. Any 47uF capacitor is fine for the supply rail, and it runs from 2.4-3.8V, and uses no more than about 30mA at peaks.

    UART_TX is the output from the BGX13P, and the CTS/RTS are not needed.

     

    image