gwiley
Experienced Member
Recently put together an M-Series Flip-Chip Tester, the original design by Warren Stearns. This is based on the variation by MThompson and PCB by Vince that was modified to connect to an FTDI C232HM interface. In this variation, the MISO and MOSI signals of all 5 GPIO expander chips are tied to common MISO and MOSI signals and each GPIO expander has its own address.
However, instead of connecting to a PC via FTDI, the tester board is connected to one of the hardware SPI channels on the ESP32 module on the proto board at the left side of the photo. Also on the proto board is a microSD card interface which is connected to the same SPI channel as the tester but is enabled with a separate chip select signal.
It’s in the early stages, but using Arduino test code I’m able to read from and write to signals via the GPIO expanders and can do file operations with the microSD, confirming the two co-exist happily on the same SPI. There is one cut-and-jump on the microSD module that tri-states MISO when the SD chip select is inactive. Could’ve done the equivalent using an extra 74HC125 but didn’t want to wait an extra day or two to order the ‘125.
Have only just started porting the tester code over to the Arduino environment but have scoped out roughly what needs to be updated. Loaded the code into Microsoft Visual Studio to play with the code a bit first.
Later on, I might control the tester using an RPi or PC, but I’m quite familiar with the ESP32 and its cousin which are in many home automation devices in my house. For my experience, this seemed like an easy place to start.
In the photo:
ESP32 on the proto board on the left, microSD interface standing up on the proto board. The microSD is for storing test vector files. Nothing wireless is being used on this ESP32, it’s just a CPU for this purpose… for the time being, anyway.
Tester board on the right with 4 SPI signals plus RESET-N cabled to the proto board. The three-conductor cable between PROBE signals and VPP and GND pins on the tester are to test reading from signals on the GPIO expanders. The Arduino test code configures the four PROBE signals as inputs with pullups so the PROBE points can be shorted to GND and confirm that data is read back properly. Test code also flashes the tester LEDs and the state of the LED signals is also read back properly. The tester PCB is slightly modified from the MThompson-vrs version.
The initial goals of this effort… play with the tester in various configurations to learn more about it through practical experience, and to be able to test M-series modules from my 8/L and some spare modules too.
I’ll post more when there’s progress, but I have upcoming travel which will certainly impact progress on fun PDP-8 stuff (again).
However, instead of connecting to a PC via FTDI, the tester board is connected to one of the hardware SPI channels on the ESP32 module on the proto board at the left side of the photo. Also on the proto board is a microSD card interface which is connected to the same SPI channel as the tester but is enabled with a separate chip select signal.
It’s in the early stages, but using Arduino test code I’m able to read from and write to signals via the GPIO expanders and can do file operations with the microSD, confirming the two co-exist happily on the same SPI. There is one cut-and-jump on the microSD module that tri-states MISO when the SD chip select is inactive. Could’ve done the equivalent using an extra 74HC125 but didn’t want to wait an extra day or two to order the ‘125.
Have only just started porting the tester code over to the Arduino environment but have scoped out roughly what needs to be updated. Loaded the code into Microsoft Visual Studio to play with the code a bit first.
Later on, I might control the tester using an RPi or PC, but I’m quite familiar with the ESP32 and its cousin which are in many home automation devices in my house. For my experience, this seemed like an easy place to start.
In the photo:
ESP32 on the proto board on the left, microSD interface standing up on the proto board. The microSD is for storing test vector files. Nothing wireless is being used on this ESP32, it’s just a CPU for this purpose… for the time being, anyway.
Tester board on the right with 4 SPI signals plus RESET-N cabled to the proto board. The three-conductor cable between PROBE signals and VPP and GND pins on the tester are to test reading from signals on the GPIO expanders. The Arduino test code configures the four PROBE signals as inputs with pullups so the PROBE points can be shorted to GND and confirm that data is read back properly. Test code also flashes the tester LEDs and the state of the LED signals is also read back properly. The tester PCB is slightly modified from the MThompson-vrs version.
The initial goals of this effort… play with the tester in various configurations to learn more about it through practical experience, and to be able to test M-series modules from my 8/L and some spare modules too.
I’ll post more when there’s progress, but I have upcoming travel which will certainly impact progress on fun PDP-8 stuff (again).