Sigma Delta Testing V00A

I have been fighting using the Sigma Delta(ΣΔ) for a few weeks now and all of my research so far has not been fruitful.  So, My intention this week is to implement a very basic ΣΔ operation that will change the prescaler for the whole range of possibilities 0 – 255.

The hardware watchdog timer triggers after about 6 seconds without a WDT reset. I have decided I want the sigma delta prescaler to step from 0 to 255 every 5 seconds.  I will put each step of the prescaler out to the serial port using system calls.

I will put all the code in the user_main.c file so that I, and anyone else that looks at my code can see all that is going on.  I extracted a new set of SDK files into a new folder called SigmaDelta.  I then created a new Eclipse project file in this new folder.    I struggled with creating the project in Eclipse.  I finally got it set up the way I wanted.  In the past setting up a project in Eclipse has always been easier, but this time it just didn’t work well for me.

I copied my shell scripts(that is batch files for windows users) that I use to automate building and testing from the UProgrammer folder. Next, I removed the references to AT_CUSTOM_UPGRADE in user_main.c and user_config.h.  I then performed a sanity check by putting one line of code to send “Hello World” out the serial connection and tried to build.  It failed because I forgot a semicolon.  I fixed that and got a new message saying code will not fit in irom0_0_seg.  I need to update the linker  file.  I copied the one from the UProgrammer folder.  Built again and it compiled. Next I uploaded it to see if it still works.  It doesn’t seem to work.  The baud rate is set to 115200, but I am getting a little bit of garbled text after boot completes.  I decided to try putting a small delay(5 ms) in before printing the “hello World”. This also didn’t work.

I need to implement a timer and looked at the sntp example in the API guide.  I set the timer to repeat every 5 seconds. Unfortunately it seems to just hang. I had a similar problem when I moved to this version of the API, I removed the uart_init line and I started getting regular data coming across the serial line. Still garbled, but happening every 5 seconds.  So I looked at uart_init from the uart.c. I found and copied the call that actually sets the baud rate.  I used this to modify the baud rate for UART0 and I started getting Hello World every 5 seconds.  Next step, turn on the Sigma Delta and start incrementing the prescaler.

I created the variables prescaler and duty and set them to 0. Then I went back to my old code and grabbed a copy of the set prescaler code.  I put the code in to set the prescaler, increment it, and print out the value every the timer event is called. I compiled, uploaded it and I saw numbers increasing across the serial terminal.  Then I waited for it to get to 100.  It continued to count.  I let it continue all the way up to 255 and then changed the wifi mode to STATION_MODE like the UProgrammer firmware. Next, I modified the code to turn on the output(GPIO4) and change the duty cycle.

Still working. Connected to wifi and tested again. Still working.  I explicitly set GPIO4 as an output set to 1 and tried again. Still working I turned on HSPI overlap mode and tried again. It started crashing and rebooting.  It looks like somehow the HSPI is conflicting with the SigmaDelta generator.

I commented out the code to set up GPIO4, and the code to connect to the wifi access point and it crashes. I changed the duty back to 0 and it doesn’t crash anymore. Next I checked the Pin assignment worksheet to see what else is connected to GPIO4 and I didn’t find anything interesting.

It looks like I have to do an HSPI overlap deinit immediately after getting data out of the RAM.  This could be a problem because I want to be generating Vpp while transferring data into the processor.  This could limit my options.  If my code is small, I can generate Vpp. If it’s large, I may have to program in blocks.

I do have the capabilities to assemble and test the voltage booster now.  I will go back into the UProgrammer Firmware code and deinit the HSPI overlap and see what happens.

I have put this week’s test code on GitHub here. How do you find problem code?

Sigma Delta still causes reboots Firmware Version 00E

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.

Update to SDK 1.5.4 Firmware V00J

Since I don’t seem to be making any progress on the Sigma Delta output, I decided to update my copy of Espressif’s API. I went to and clicked on the SDKs thread under the heading DOWNLOADS. In the list i looked for the most recent Non OS SDK release.  I saw that ESP8266_NONOS_SDK_V1.5.4_16_05_20 is the most recent release. It’s file name indicates a release date of May 20th 2016.  I downloaded the zip file and extracted the contents.

To Make moving forward a little easier, I renamed the SDK folder to UProgrammer.  This will help me maintain paths the next time I move to a new SDK Version.  Each time I update to a new SDK, I will Rename the OLD SDK folder to indicate it’s version number, and rename the new SDK folder to UProgrammer.  To maintain compatibility with Github’s folder naming, I will continue to keep the UProgrammer-Firmware folder name for the project files.  This folder will be sitting in the SDK folder I just renamed to UProgrammer.  I then created an empty text file with the name of the SDK file to mark the version I am working in.  Then I copied the hidden file .metadata from the old SDK folder into the new (UProgrammer) SDK folder.

I opened eclipse and pointed the workspace to the UProgrammer folder and it loaded the files as if I hadn’t changed anything. Then I made edited the comment block at the top of the file to indicate I had moved to NONOS SDK V1.5.4.  I saved the file and then checked the file in the new directory structure for the changes. It has the change I had just made.  To make sure there wasn’t something weird going on, I also checked the file in the old directory structure. It was unchanged.  I had planned on dealing with more problems just in case they happened.

I compiled the code to see if anything broke moving to the new SDK.  Things definitely broke. First the files all compiled but linking failed.  The first error message was:

section `.irom0.text' will not fit in region `irom0_0_seg'

This reminded me that I modified the linker file to allow for more room for the code space in a 4MByte flash chip.  I made the modification to the new file and saved it.

Modified linker file

I tried compiling again.  Again it failed to link but I was no longer getting the memory failure. This time the first error message was:

 undefined reference to `uart0_sendStr'

I didn’t have the most recent programming reference, so I went back to to download it.  I got the 2C-ESP8266_SDK_API Guide_EN_1.5.4.pdf.  It turns out uart0_sendStr() isn’t in the documentation.  So I looked in my code to find it.  I found the prototype for it in uart.h. but it doesn’t appear anywhere else. This makes me wonder how I was compiling last week.  I did find it in uart.c in the drivers folder.  At one time that file was part of the project. I am guessing the object file was still getting linked in to the project.  The compiled object files are in hidden folders and didn’t get copied by default.  (It’s a good thing.  The versions of code on Github would not have worked. Now they will get fixed.)  I copied The code for uart0_sendStr() into simple_serial.c and recompiled expecting it to fail because uart0_sentStr() calls something else in uart.c.

Again I looked at the first error from the linker which was:

../lib/libat.a(at_ipCmd.o): In function `at_set_rx_buf_state':
(.irom0.text+0x10ac): undefined reference to `espconn_secure_sent'

I am not using any secure features or any AT functions, so I decided to look at the make files. I used a Linux tool called meld to compare files.  There were very small differences.  Looking at my makefile, I noticed four lines that effectively added the -lat linker option.  I commented out those 4 lines and recompiled.  Now the linker only has 4 errors remaining, all of which can be fixed by copying code from the uart.c file.  After copying each function I needed from uart.c, I finally got a successful compile of the code.  I then uploaded it to the PCB to see if it still runs.  It ran the wrong code.  I now get a message in the serial terminal “dmode : softAP (XXX) indicating it is booting up as an access point.

I was able to connect to the device and dhcp worked, but an attemp to connect by http was refused.  Since the messages are system messages I decided to try a UART Swap. No change in the behavior.  I need to do a sanity check, this is a new API so back to doing a Hello World test. I finally got confirmation that my code is what is being uploaded to the module.  I placed the following function call:

system_set_os_print(0); // Turn off System Messages

into the code. I am no longer getting any output in the terminal.  I wasn’t getting any error from compiling but it turns out the function uart_tx_one_char() needed to be copied from the uart.c to simple_serial.c I chose not to have uart.c to reduce code size, there is a lot of code in uart.c that I will never use.

I cleaned up some of the things I tested recompiled and posted a new copy to Github. Do you have any tips for migrating between environments? I’d love to hear about them.

Sigma Delta still causing resets.

When I first built this revision of PCB, the board would reboot a lot.  That turned out to be the mis-wiring of the SPI RAM.  Part of that process in trouble shooting that board, I had guessed that I had a noisy power connection to the Wi-Fi module. So one thing that I had tried was adding a large reservoir capacitor and a small filter capacitor near the power pins of the module. Unless I am drawing too much current from the voltage regulator, this should eliminate any possible power issues.

This means my first test is to measure how much current is being drawn from the voltage regulator.  To do that I removed the jumper that bypassed the lithium cell charger and attached 3.7V to the PCB from a bench power supply.  To do this I removed all the test pins I had soldered to the module and soldered one to +BATT and another one to GND.  I connected my meter in series with the power supply and turned it all back on.  I measured the current consumed between 75 and 80 mA for the whole range of 0 to 99 prescaler.  This measurement was made with the radio inactive.

I think I can rule out the power supply as my problem.  Next I decided to change the software to take steps of 10 instead of 1 for adjusting the prescaler.  If the failure is because of an accumulated error, this should happen later and I should be able to get a number larger than 100 without a failure. I re-soldered the  bypass of the Lithium Cell charger and uploaded the change. I got to 91 No Failure. At 101 it still failed.  I change the step to 30 and when I got to 120, I got a reset cause:2. (maybe there is a clue here, This means external reset.)  I found this in the 2c-ESP8266_SDK_Programming Guide.pdf file from the Espressif BBS.

There are two pins on the module that can be used for external reset.  Since the serial to usb bridge is controlling the reset line, I decided to look into the EN pin first. It looked good with the right resistor in place to pull it up.  I then started looking through the code to make sure the Sigma Delta was configured to the correct pin.  Turns out that it wasn’t configured to output on any pin.  There was a missing statement in the code setting pin4 to output the sigma delta channel.  I added that line back in, saved, recompiled, uploaded and tested again. It still is failing.

Going back to the external reset, I decided to put lower value pullup resistors on the reset lines. I changed them from 10 K to 1 K.  This should reduce any affect of noise on the pins and still not draw too much current when pulled low. It still fails in the same way.  I have another project where the sigma delta is working very well.  The main difference I can see is that on this project I am reading the sigma delta twice before I write to it. In my other project, it reads the register once.  So I am going to make a simple uint8 variable to retain the value I am writing to the Sigma Delta prescaler.

It is still not fixed.  Have you seen this problem? Have you solved it?