An ESP32 in the Raspberry Pi form factor
For applications, where the Raspberry Pi 4 is not robust enough, or take too much power, you can consider the EsPiFF as an option. The EsPiFF (V2) brings
- ESP32-WROVER with dual core, 8MB PSRAM, 16 MB Flash
- Ethernet wired and Wifi
- SD-card for data storage
- up to 3 UARTs
- an USB-C connector for power supply up to 5V, 3A
- a Rasperry Pi header with 40 pin, compatible to all Raspberry Pi HATs
The EsPiFF V3 will bring the following
- an RP2040 IO-processor additional to the ESP32
- 2kByte FRAM for high-speed permanent storage
- RTC Realtime clock
- USB-A connector for USB-Host
We decided to build an alternative to the Raspberry Pi for our projects and products. As many others we were using the Raspberry Pi in our products, adding electronic payment to existing vending machines and coffee machines, in RFID solutions to read RFID tags in laundry and other application. While it was easy to get a solution up and running in a short time, over time we got a lot of problems resulting from using the Pi. A key problem of the Pi's design is, to rely on an SD-card. The SD-cards are made for digital cameras, to write on them a few times. A Linux system like the Pi on the other hand, is writing permanent its log files and swap partition or to the SD-card. As a result, after some months the SD-card broke and the application crashed. High-end industrial SD-card lasted longer, but finally still broke. An industrial controller simply can not base on a SD-card. The PI Operating system is also great for fast bring-up of a solution, but its more and more focused on media streaming then real-time tasks. It gets more and more overloaded with each new version. So we made the decision, to build a replacement, which is focused on high-reliability, but still enable the use of Raspberry Pi universum of add-ons, like HATs and enclosures. We choose the ESP32 dual core, 2x240MHz WROVER module with 8MB PSRAM and 16MB Flash. The EsPiFF, the Esp32 in Raspberry Pi Form Factor was born.
The first version of the EsPiFF was born in a time, where all Ethernet Phy chips was unavailable. Our first prototype used a Waveshare LAN8720 module. Chip crysis! Interestingly, even no LAN8720 chips could be bought anywhere, but the modules was still available. Because the Waveshare module did not route the enable signal to the pin header, but left one pin unconnected on the pin header, we had to solder a wire from the oscillator to that unused pin on the header. After these, the board run well, and do so till now. We added 4 high side switches, and digital inputs to operate 4 door locks. These are the 4 white connectors opposite the RJ45 connectors. The Version 1 had the WROOM module of the ESP32.
Picture: the Version 1 of the EsPiFF
We ported the PostgreSQL client libray, based on SimplePgPSQL to the EsPiFF, what worked very well, even with the limited RAM and Flash. Not only SELECT, INSERT and UPDATE work, but also the brilliant PostgreSQL feature NOTIFY. As a result, the EsPiFF dont need to poll the PostgreSQL server, but get notified instead. We could define a trigger in PostgreSQL, and notify other EsPiFF board. Thats very cool.
Because of the ongoing chip crysis, we only select parts, what are available.
After the LAN8720 chips got available again, we decided to make a new board revision. These are the current boards. We used the ESP32-WROVER module, for additional 8MB PSRAM and 16MB Flash. We also added an SD-card. Unfortunately, we used the wrong pinout, make it very difficult to change the SD-card. An other issue was a missing pull-up resistor on the LAN8720.
We changed the USB connector to a Type-C connector, and configured it so, that 5V and up to 3A can be taken. Thats a big improvement, raising the available power from 0.5W to 15W. We removed the 4 door lock connectors, and put them on a HAT.
Since version 1 we have a "Chafon-Connector", next to the USB connector. It is to connect the Chafon RFID Rain(UHF) modules. Additional, we replaced the UART pin headers with more robust JST connectors, left and right of the SD-card.
We could also compile and flash the Apache Nuttx operating system on the new board. A growing number of people are using ESP32-WROVER boards together with Nuttx as OS. This offers an somehow easy path of porting Linux and Raspberry Pi software on ESP32+Nuttx.
This is the planned final version. Additional to the fix of the 2 known issues, we plan the following:
- adding a I2C-RTC: a real-time clock will be needed for planned PLC usage.
- adding a 2kByte FRAM: again for PLC application, a fast and non-volatile memory is needed. It offers near infinity write/read cycles compared to flash.
- replace the WROVER module with a version with u.FL/IPEX connector. This enables an external antenna, longer range, mounting inside a metal enclosure with the antenna outside the enclosure.
- adding a RP2040 co-processor. The ESP32 just not have enough pins free, to operate all the pins on the Raspberry Pi 40pin header. The last solution with the I2C port expander is too slow and unflexible. The much more powerfull RP2040 will solve these problem. It also offers an USB host port!
- add a USB-A connector, to program the RP2040, and to enable to connect USB devices like keyboard, mouse, USB-sticks and so on.
- add an HMI connector next to the SDcard socket. This is for our upcomming TFT displays, but can be used for UART based TFTs like the Nextion as well.
This is the current progress. We managed, to bring all the functionality on the board. We selected a 6 layer PCB, for best signal integrity.
We finally replaced the LAN8720 Ethernet PHY by an IP101, as used in the Espressif Ethernet reference design. The LAN8720 showed stability problems, in combination with the ESP32-WROVER (it is working well with the ESP32-WROOM). Other projects with the ESP32-WROVER - LAN8720 combination (wESP, Olimex) seem to had the same problems, and also switched away from the LAN8720. On this point, a big "Thank you" to Ondrej from Espressif for all of his support in this field.
We also ordered customized cables, for the DF11 and display connectors, what offer DuPont on the opposite side. With these cables, breadbord or Nextion displays, or other 2.54mm headers can easily connected.
This example show, how a Nextion 5 inch TFT, a HF RFID reader from Elatec (TWN4), a Chafon 8 channel RAIN UHF-RFID reader and a 3D printed enclosure can form an electronic identification system. We put the source code and the 3D design files into the example folder. Smaller or bigger Nextion TFTs can be used, when you adapt the 3D design.
The HMI interact with the user, ask him/her to put the HF-RFID card on the card reader. The TWN4 from Elatec is able to read near any LF or HF card, inclding the LEGIC chips used in many high secure access control applications. The TWN4 is inside the 3D printed enclosure, as well as the Nextion TFT.
With the 8 port RAIN UHF reader/writer from Chafon, we can monitor a whole area with up to 8 antennas. We use it to monitor 4 cabinets, other use cases could be the monitoring a whole room/warehouse, or the entrance of buiildings,etc. Chafon offer 1, 4, 8 and 16 port devices, and they are all compatible with the software.
In our application, we read/write direct to a PostgreSQL database, connected by wired ethernet, thats why we have ported the LibPQ (the PostgreSQL client library) to the ESP32. The use of other techniques, like MQTT, is also possible.
Picture: the open 3D printed enclsure, showing the Nextion 5'' TFT, and the TWN4 HF RFID reader
After the EsPiFF is now mature enough, we we are preparing a campaign at Crowd Supply. After the Pre-launch page will be available, we will update the info here. Hope you support us on our Crowd Supply campaign!
Team MDC