Tag Archives: ESP-12F

Refactoring Electronics (Hardware V00K)

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Side Project:

I still haven’t gotten the OLED display working.  I am beginning to question Pinouts and even if the driver IC listed by the seller(s) is correct.  At this point I can’t even tell if the device is seeing my commands. I checked the board for shorts/solder bridges and even replaced the OLED display. I still can’t get anything to show up on the display.

I think a reasonable test would be to measure current to the display and send it a power on command.  If I am sending commands correctly, I should see a change in current draw.  After that, I will try working through the commands available in the datasheet for a SSD1332 chip looking for a change in the display or the current draw.

Refactoring:

Just like refactoring the code, It’s time to refactor the electronics design.  I checked on my feature request on the Espressif forum. Nothing new has happened.  So I am considering adding an external ADC to measure voltages.

Planning and Research:

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Design Decision

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Side Project:

I am moving forward with the Compass toy prototyping.  I am designing a simple breakout PCB for testing the display. I may put the display breakout for sale on Tindie.

Project Intent:

The primary goal of this project/blog is to show electronics design start to finish.

The design goal is an inexpensive in circuit chip programmer that will work for most devices available.

Options:

The Raspberry Pi Zero was released November of 2015 at a price of $5 US each.  I even got one with a copy of MagPi.  To Make it run any code at all, it needs a power supply and microSD card.

Of course I could continue with the current design.

Common components:

Both the Raspberry Pi and the current design need the following components.

Printed Circuit Board
Battery for power supply and charging circuit
Vpp Supply
Level Shifter Circuit
External ADC(Still undecided for current design)
USB to serial Bridge (not sure it’s necessary for R Pi)

Additional components for Raspberry Pi:

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New Build

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Update:

The level shifter came in this week.

Populating the board:

I installed parts out of my kit in the order that I grabbed them, until I had enough to do the basic test.  The board powered up and the blue LED on the ESP-12F blinked once.  Unfortunately the board wouldn’t program.

I started probing with my Oscilloscope.  The serial data lines looked normal when I tried to program the board. Then I looked at Reset and GPIO0 lines and found that GPIO0 was oscillating at 24 MHz. The Reset line was working as I expected it to.  I used a 1 MOhm resister as a pull down on GPIO15. I chose 1 MOhm to reduce the amount of current when A_Sel is High.  I knew this could cause me trouble, GPIO15 is used to put the chip into SD card mode. That may be too much resistance.  I changed that resistor to 10 KOhms to see if it made a difference. It did!

I uploaded the defaults, then my code. My simple serial menu came up in the terminal. With it working, I went on to populate the rest of the board.  I came up short 2 components, the pin header I use for the lithium cell and Q2.  I grabbed both of those from the last build and completed populating the board. I reconnected it to my computer, re-connected the serial terminal and the serial menu is still working.

SPI RAM Testing:

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Layout check … continued

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With the new check plots I made last week, I checked the layout net by net like I did back in Sept 5, 2015. I am still uncertain about the pinout of the ESP-12F modules. To test it, I removed the ESP-12E installed on the board I am currently using, and replaced it with a new ESP-12F.  I had to be careful that the jumper wires all got back to where they were before removing the module.

The new module programmed first try but didn’t boot correctly.  I had forgot to upload default values, the flash comes programmed for a different memory layout.  Once I installed the default settings, it booted up correctly.  I had removed the test for HSPI/SPI RAM, so I went back into the code and re-enabled the Hello World ram test.

I went into serialInit() and changed the line DISPLAY_MENU(); to DISPLAY_MENU_W_SPI(); Re-compiled and tested.  Unfortunately the result was not “Hello World”. When I cleaned up the code, I made the write to SPI RAM easier, but I need to initialize the hspi.  I started connecting my mixed signal oscope to analyze what was happening on the SPI bus.  And… I found a loose jumper wire.  The one that connects the chip select between the ESP-12F and the SPI RAM. Once this was connected, the extra stuff I had put into the software became unnecessary.  I deleted the extra code and it works just fine.  The firmware is back to where it was before I started testing. There are no changes to upload.

This means that the circuit is tested and the current layout is ready to send to fabrication.  I zipped up the gerber files. Then checked pricing with PCBway, DFRobot, and Seeed Studio.  With shipping PCBway came in a little less at US $19.  With PCBway, I have to wait for a design review before they will give me a final price and allow me to pay for it. Usually this is pretty quick but depends on the day it is submitted.

Have you bought boards from Chinese manufacturers? How quickly did you get them?

Hardware Iteration (hardware V00H)

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The last time I worked on the electronics was when I got the switching boost circuit working.  The crashes I saw with it is why I did so much code work since then.  This week, I wanted to get back into electronics.  Since it has been a while I started by reviewing the schematic.  First thing I reviewed was the Lithium cell charger circuit.  It matches the reference design in the AAT3672 datasheet and it matches the PCB.  I should test it before I spin another set of boards.  I put a note on the schematic to remind myself to do that.

I then looked at the switched boost circuit. It turns out I don’t need L2, the real problem was in software. I removed L2 from the schematic. The resistor R5 was changed to 47 Ohms. I updated that on the schematic.  Next I looked at the USB to Serial Bridge, I have two cuts with Jumpers on the board, I checked them against the schematic. The schematic matches the patch I had made.

Next I compared the patches I made to the SPI RAM against a pinout of the ESP-12F I found online.  ESP-12F pins 9 – 14 on the schematic matches the PCB with the modifications I have made.  Pin 16 is no longer connected and Pin 18(GPIO0) is connected.  I had made this change back when I was testing the SPI RAM. With this change, D4, Q6, R26, and R27 are unnecessary. I removed them from the schematic and tied GPIO0 to U2 Pin1 and disconnected it from U10 Pin 6. I then tied GPIO15 to U10 Pin6 with a net label called A_SEL.  I have yet to test IO2 and IO3, Which will require running the RAM in QIO mode. In QIO mode, IO2/IO3 shouldn’t matter because when I read them back out of the RAM will come back out on the same pins they went in.

I have yet to test the level shift chip(U3).  I don’t like how hard U3 is to solder so I researched a different part to do the same thing. The new part I found is a TI TXB0108PWR which works very nearly the same as what I already had designed in but comes in a 20 pin TSSOP which is easier to solder.  The Pin order is different. The part is only US $1.88 in singles at Digikey.  I proceeded to change U3 to the new part on the schematic.  The datasheet recommends that OE be held low until both Vcca and Vccb are on.  I put a PNP transistor in to pull OE low anytime Vt is not driven.  As I dug into the datasheet, I found that this chip would not work for I2C.

So I did a little more research and I found another chip from TI.  The TXS0108EPWR works with SPI and I2C.  It has the same pinout as the TI TXB0108PWR so adding it to the schematic was really easy, I changed the name in the schematic.  This part is US $2.00 on Digikey.

txs0108esch

I uploaded the updated hardware design to Github. Click on the hardware link in the right column to go get it.

Have you used level shifters before? Have you decided on a chip only to find out that it was missing one crucial component? How did you fix it?

Sigma Delta still causes reboots Firmware Version 00E

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I was hoping but not expecting the SDK Update to fix the Sigma Delta problem.  So first thing I did this week was to test.  Same failure as before.  I had two Ideas this week that might be an answer to the problem.  On another project, I was using the Arduino IDE to develop a little weather station project.  In it, I was using old code that set certain pins as output.  Those pins were/are tied to the SPI bus and was causing it to reboot.  Maybe, there is a pin set to have Sigma Delta(ΣΔ) output that is also tied to a critical pin.  My second thought is that if the ΣΔ is causing interrupts, I should disable them.

A good practice for microcontroller programming is to always set up all I/Os immediately after a reset.  I have gotten sloppy and haven’t done that with this project. If a pin is connected to the ΣΔ that shouldn’t be, this will fix that.
I started by writing down what each pin will do in the design. I referred to the schematic for each pin.

Pin 18 GPIO0 -- Output -- controls analog switch
Pin 22 GPIO1 -- Output -- TxD0
Pin 17 GPIO2 -- Output -- sets VPP output high
Pin 21 GPIO3 -- Input -- RxD0
Pin 19 GPIO4 -- Output -- ΣΔ pulse stream to generate Vpp
Pin 20 GPIO5 -- Output -- Sets Vpp output low
Pin 14 GPIO6 -- Output -- SCLK (SPI and HSPI overlap) (need to verify Pin number for ESP12F)
Pin 10 GPIO7 -- BiDir -- MISO (SPI and HSPI overlap) (need to verify Pin number for ESP12F)
Pin 13 GPIO8 -- BiDir -- MOSI (SPI and HSPI overlap) (need to verify Pin number for ESP12F)
Pin 11 GPIO9 -- BiDir -- QIO2 (SPI and HSPI overlap) (need to verify Pin number for ESP12F)
Pin 12 GPIO10 -- BiDir -- QIO3 (SPI and HSPI overlap) (need to verify Pin number for ESP12F)
Pin 9 GPIO11 -- Output -- CS0 (SPI) (need to verify Pin number for ESP12F)
GPIO12 -- BiDir  -- Data to target device
GPIO13 -- BiDir  -- Data to target device
GPIO14 -- BiDir  -- Data to target device
GPIO15 -- Output -- Chip Select for HSPI
GPIO16 -- Output -- Disables Vpp generation

I went into the user_init() function and removed all the commented out code leaving an example of the PIN_FUNC_SELECT() macro. I then set GPIO_PIN0 – 15 registers to 0 which disables interrupts and disconnects the ΣΔ output.  I compiled the code and uploaded it and it crashed.  To find the new problem I caused, I commented out all the new code except setting the GPIO registers to 0. I rebuilt and uploaded the code and … a continuous stream of reboots.  I commented out setting the GPIO registers to 0 then put the PIN_FUNC_SELECT() back in. And … reboots slowly.

I removed the function selects that should be controlled by the API anyhow(GPIO6-11). And … I found a typo on the GPIO6 function select. I fixed the typo, rebuilt, uploaded and it ran at least as well as last week.  I then started testing to see if it fixed the ΣΔ issue. The reset problem still exists.

Next I set a subset of the GPIO registers to a value of 0  I decided to go with the first 8 to see what would happen. Same failure, a stream of reboots. Then I noticed I wasn’t writing to the correct register locations.   I fixed this and then recompiled, uploaded, and code is running, but ΣΔ is still causing a reboot if i set the prescaler to greater than 99.

Next I started looking at the ΣΔ interrupt structure.  Unfortunately it has very little documentation that I have found so far.  I used google to search for articles pertaining to the use of the Sigma Delta and found very little.  My next step is to do a little experimentation. I decided to disable the ΣΔ while changing the prescaler.  I got the same results.  It’s time to make a Hello World program for a sanity check. It would be the minimum to set up and test functionality of the ΣΔ on GPIO4.  If it works correctly, then I have to take a deeper look at my code, if it doesn’t, I’ll have something to post to Espressif’s forum for help.

Have you had similar problems with a chip you have never used before?  I have uploaded the current code to GitHub. Use the link at the top of the right hand column to get the download.