Programarea unui ESP32 fara Arduino IDE

Placile Arduino deja fac parte din istorie iar hobbystii deja au la dispozitie platforme de experimentare tot mai puternice din punct de vedere al interfetelor oferite.

Espressif a iesit pe piata cu ESP32, un MCU ce incorporeaza periferice IO digitale, ADC-uri de inalta rezolutie si WiFi/BLE, totul intr-un pachet miniaturizat si cu consum extrem de redus ce il face deosebit de versatil pentru proiectele care incorporau pana acum platforma ATMEGA.

Pretul comparabil sau chiar mai scazut al placilor de dezvoltare  bazate pe SOC-ul ESP32 a determinat migrarea multor proiecte spre aceasta platforma iar  IDE-ul Arduino a primit bibliotecile necesare pentru a fi compatibil.

Uneori insa, suntem in situatia de a avea fisierele gata compilate, exportate din IDE Arduino sau alt mediu de dezvoltare si dorim sa facem programarea cu un alt calculator ori am primit fisierele de la altcineva care nu doreste sa faca public codul sursa. 

Cu ajutorul aplicației ESP Download Tool este posibilă încărcarea programelor compilate (fișiere BIN) în ESP.
Acest articol se referă la pregătirea utilitarului și la diferiți parametri necesari pentru transferarea cu succes a acestor fișiere.

Pasul 1, descarcarea aplicatiei ESP Download Tool

Programul este oferit chiar de producatorul Espressif iar descarcarea se face sub forma unei arhive.

Dupa descarcare, dezarhivam fisierele; vom obtine un folder in care se gaseste un fisier .exe si alte subfoldere necesare functionarii aplicatiei.

 

Pasul 2, rularea aplicatiei.

Este de retinut ca aplicatia ruleaza direct, fara a fi necesara instalarea ei. 

Programarea cipului are loc insa pe o interfata UART, seriala, asadar, daca calculatorul nostru nu are port COM nativ sau programarea se realizeaza prin intermediul unui adaptor USB<>UART, este posibil sa fie nevoie sa instalam unele drivere in cazul in care Windows nu le instaleaza automat. 

In general, placile de dezvoltare au deja acest adaptor USB<>UART incorporat in design; in imagine, o placa MCU32 Devkit cu circuitul adaptor CP2102.

Pornim aplicatia ESP Download Tool din executabilul flash_download_tool_3.x.x.exe; se vor deschide doua ferestre; una de tip Terminal (care va afisa datele in timpul operatiunii de upload) si a doua, pentru selectarea tipului de MCU ESP. Cu acest software se pot programa si ESP8266 precum si toata gama ESP32.

 

 

Chip Type: Daca lucram cu un modul ESP32 WROOM (atentie la inscriptia de pe ecranul metalic), atunci selectam
"ESP32-D2WR" iar pentru restul, in marea majoritate a cazurilor putem folosi optiunea generica "ESP32".

WorkMode:  Intotdeauna alegem "Develop". Modul "Factory" este destinat programarii mai multor MCU simultan.

 

Pasul 3, conectarea ESP32 la calculator.

Acum este momentul sa conectam placa de dezvoltare la USB  direct sau prin intermediul adaptorului USB<>UART.

Verificam in Device Manager daca driverul este instalat si functioneaza.

Unele placi de dezvoltare necesita apasarea unui buton in timp ce sunt conectate la USB; acesta este notat "FLASH" sau "BOOT" si nu trebuie confundat cu "RESET" sau "EN"!

Pasul 4, setarile aplicatiei.

Înainte de a selecta fișierele BIN și adresele sectoarelor de memorie, trebuie selectați unii parametri pentru ESP32.
Practic, majoritatea plăcilor ESP32 ar trebui să funcționeze cu următoarele setări:

SPI SPEED: 80 MHz
SPI MODE: DIO
Dimensiunea Flash: 32 Mbit (4 Mbyte)

În plus, trebuie să se specifice portul COM în software.
Viteza de transmisie (BAUD rate) este setată la 921600.
Abia după aceea este necesar să fie specificate căile către fișierele BIN și sectoarele de memorie.

Pasul 5, selectarea fisierelor BIN si a adreselor locatiilor de memorie unde trebuie incarcate.

Programul oferă posibilitatea de a încărca mai multe fișiere BIN în același timp. 

Astfel, nu numai programul propriu-zis, ci și bootloaderul sau partițiile pot fi încărcate în ESP32. 

Deoarece, în principiu, un bootloader este întotdeauna deja instalat pe plăcile de dezvoltare înainte de livrare, in cele mai multe cazuri, acesta nu va trebui încărcat. 

Este suficient să încărcați doar fișierul BIN cu programul principal.

Aria pentru programul principal începe întotdeauna de la:: 0X10000
Ambele câmpuri vor deveni verzi dacă datele au fost introduse corect. 

Cu un clic pe "Start" începe procesul de încărcare. 

Dacă acesta a avut succes, acest lucru este confirmat cu "FINISH" (Terminare). 

De îndată ce se apasă butonul de Reset (sau EN) de pe controler, programul încărcat ar trebui să pornească.

2024, Copyright YO3HJV

 

MESHTASTIC TTGO T-Beam V.1.1 Power On issues

 A few weeks ago, I start to play with Meshtastic using two TTGO - TBeam V.1.1 LoRa boards based on ESP32 MCU.

Because plans are to use them as ROUTER_CLIENT, I choose to recharge the battery using a separate TP4035 module and a solar panel.

Of course, I could very well use the built-in AXP192 battery management but the circuit was pretty unsuitable for small solar panels and the TP4056 offers a more stable configuration. 

In the tests I observed a strange behaviour that can negate the usage of these boards as a reliable remote installed device: 

if the battery voltage drops under the Low voltage treshold, the board will not boot into operating mode.

The same behaviour was consistently observed even the charging was resume on the USB port on the T-Beam board itself.

The ESP32 datasheet have some clues about why this issue occurs and how to mitigate it.

Once the power is supplied to the chip, its power rails need a short time to stabilize. After that, CHIP_PU – the
pin used for power-up and reset – is pulled high to activate the chip. For information on CHIP_PU as well as power-up and reset timing, see Figure 2-4 and Table 2-2.

• In scenarios where ESP32 is powered up and down repeatedly by switching the power rails, while there is a
large capacitor on the VDD33 rail and CHIP_PU and VDD33 are connected, simply switching off the
CHIP_PU power rail and immediately switching it back on may cause an incomplete power discharge cycle
and failure to reset the chip adequately.
An additional discharge circuit may be required to accelerate the discharge of the large capacitor on rail
VDD33, which will ensure proper power-on-reset when the ESP32 is powered up again.
• When a battery is used as the power supply for the ESP32 series of chips and modules, a supply voltage
supervisor is recommended, so that a boot failure due to low voltage is avoided. Users are recommended
to pull CHIP_PU low if the power supply for ESP32 is below 2.3 V.

I run some tests and found that if the above hints are observed, the recovery of the ESP32 from transient voltage induced coma is 100% so a supervisor chip was ordered.

The STM1001 microprocessor reset circuit is a low-power supervisory device used to monitor power supplies. It performs a single function: asserting a reset signal whenever the V_CC supply voltage drops below a preset value and keeping it asserted until V_CC has risen above the preset threshold for a minimum period of time (t_rec).

To be continued...

LATER EDIT:

The STM1001 finally arrived (after three days) and I was eager to test the validity of my rationale.

 

 

So, I installed it on the board; the Vss was soldered on a little island of Copper exposed by a sharp razor and the Vcc was tied to the Source pin of the P-channel NCE3401 MOSFET.

 

 

This transistor is there to protect the board against reverse polarity from the battery.

The RST of the STM1001 was tied to RST of the T-Beam board.

And here it is, the final installation:

Now, for the tests...

There are two distinct situations, depending on how the battery is charged; internal or external.

 

FIRST VARIANT - battery charged internally, using the AXP192

The battery is directly installed on the board and the AXP192 circuit is used at it's full. 

The battery is a small capacity one (1.28 Wh), to be able to have it quicly charged to observe the parameters.

The battery is charged by AXP192.

Going from a flat battery (around 2.5V), the  voltage of the cell, measured at STM1001 Vcc and Vss.

The blue LED is signalling the charging, the voltage is rising and when it reached 3.19V (on my DVM), the RST is released from Vss to 3.2 V (the Vcc of the ESP32).

The ESP32 start to run, the LoRa RTX is sending the first beacon.

This was consistent during a set of 5 tests.

SECOND VARIANT - battery charged externally through a TP4053 board.

The same battery is connected to a TP4053 board with protection and the output of the board is connected to the T-Beam board in place of it's battery.

The AXP192 is not able to manage the charging process because it cannot detect the external power presence.

Therefore, the AXP192 will not start and will not be able to Power On the T-Beam board, at least in the current firmware used for Meshtastic.

Due to the way it works (it is a very complicate process - if you don't believe me, read the AXP192 datasheet) it is mandatory to simulate PEK press (Power Enable Key) after the voltage reach 3.2V which is beyond my scope.

I did some crude tests and it is doable but the solution will be more complicate than the one I am searching for.

 

TC4056 1 cell LiIon charger module

I have a lot of those little boards made around a TP4056 IC.

According to the datasheet:

The TP4056 is a complete constant-current/constant-voltage linear charger for single cell
lithium-ion batteries. Its SOP package and low external component count make the TP4056
ideally suited for portable applications. Furthermore, the TP4056 can work within USB and wall
adapter.
No blocking diode is required due to the internal PMOSFET architecture and have prevent to
negative Charge Current Circuit. Thermal feedback regulates the charge current to limit the die
temperature during high power operation or high ambient temperature. The charge voltage is
fixed at 4.2V, and the charge current can be programmed externally with a single resistor. The
TP4056 automatically terminates the charge cycle when the charge current drops to 1/10th the
programmed value after the final float voltage is reached.
TP4056 Other features include current monitor, under voltage lockout, automatic recharge and
two status pin to indicate charge termination and the presence of an input voltage.

This might be a problem with low capacity cells because to keep the charging in the safe area, the charging current must not exceed 1C (C=designed capacity).

Charging above this might give a temperature rise and this is not good for Li based cells. Of course, there are specific cells that accept charging currents above this safety limit but those are special ones thus not taking risks is a good approach.

Going to the datasheet of the TP4056 give us some interesting informations.

We can conclude that we can use this circuit directly connected to a small Solar panel able to output 6V.

But what about the current? 

Well, the charging current is set by the value of a resistor, Rprog in the test circuit below:

 The value of this resistor determine the charging current as per the table below:

On some modules, the resistor is marked "R3" but anyway, you can easily found it by tracing the circuit from the pin#2 of the IC; in the photo is the one below the little capacitor on the left side of the circuit:

From the factory it came with a 1K resistor which, according to the datasheet, correspond to a 1000mA (1A) charging current.

I changed it with a 2.2 KOhm one and the charging current dropped, as expected, around 500mA.

For final, here is what this module wants to tell us, based on the LED status:

 

Portable GPS barometer UTC Clock

 

Often, in portable I have to use the phone to check for Maidenhead QTH Locator and UTC for logging purposes.

Looking into my junk box I found that i have a lot of ESP based development boards (NodeMCU) and even a uBlox GPS that I bought several years ago and never put it to work.

Also, a small 1.28" SPI TFT was there, waiting...

So, I made a little box usefull for portable/outdoor ham things...

The main feature of this box is to show the UTC and Maidenhead locator as we use this very often into the field but working on this project I thought why not add a barometer and see the pressure.
The next step was to show the evolution of the QNH in time to see if there are some worring variations and a little graph was added.

So, overall, here are the features:

- GPS Coordinates; Lat, Lon, Alt (this need good GPS reception).

- UTC time;

- Maidenhead Locator with 6 symbol precision, good enough for sending it to a correspondent.

- QNH with graphic representation.

- Battery voltage indicator for the LiIon cell.

 The barometric pressure is read at about 15 seconds and averaged for 10 readings then a pixel is drawn on the TFT graph area. For 126 pixels, we will have a history of atmospheric pressure for the last around 45 minutes.

The colours can be easy changed by changing the code.

My little box is powered by one 2000mA LiIon cell which can give around 7 hours of usage. 

The code is available on GitHub.

 

Microphone preamplifier for DC powered (phantom) input

I found this by the grace of FB who reminded me about it (10 years).

A customer came with a specific request: to increase the volume of the headset microphone for his AM Air band transceiver.

If I remember well, it was a ICOM AM transceiver.

The problem was that the space was very small inside that helmet and the second, and bigger, problem was that the microphone had around 8V DC phantom power.

An intervention in the radio itself was excluded because, you know, "life support device" and going inside it was a no-no...

The solution I found was a small preamplifier for both of his headsets (two pilots there).

The schematic:

The PCB was draw by hand. Pretty ugly but it fitted perfectly in the helmet and by using SMD components, the result was very solid: