3 (or 4 or 5)-chips Z80 SBC

01/24/2017 Posted by admin

I have started working on a Z80 board that would use only 3 parts (Z80, RAM, Glue logic+SIO).

The Glue is done via a PSoC4 from a Cypress CY8CKIT-049-42xx (<5 euros…) – Currently the Flash chip is not used, and only 64KB from the RAM (128K) is used. Z80 is clocked at 9.6Mhz.

There is provision for RAM & ROM bank switching in the future (or not… maybe it would be better to replace the flash by an sdcard)

It has started working… If you count the serial-to-usb chip on the CY8CKIT, that’s a 4 chips Z80 board – if you count the CY8CKIT as one chip, it is a 3 chips board…


With Z80′s reset line low, via a bootloader, Grant Searle’s Basic is sent from the PSoC4 memory to the RAM and the Z80′s reset is set to high.

ESP8266 : Using a sledgehammer to crack a nut

09/14/2015 Posted by admin

As almost everybody, I have ordered a few esp8266 modules.

For me, the existing examples are not using enough ressources of the chip : it is a 80Mhz device, with lots of memory, so… why not trying to put some old code for the ZX81 emulator on the STM32F103, and try to have it run on the ESP ?

So here is :

Blinky on the ESP8266, but through a Z80 emulator running a ZX81 Basic ROM

See the video on Youtube.

Keyboard/Display is currently using an UDP connection to a small and ugly Python client on a PC (semi-graphics not implemented).

It is able to run ‘galaxian’ … ;-)

Code is available on Github.


Troubles programming Sparkfun Pro Micro from Ubuntu

09/11/2014 Posted by admin

It took me a while to figure out what was wrong with my ProMicro…

When trying to program it from Linux/Ubuntu, avrdude was not working, with the following error :

avrdude: ser_open(): can't open device "/dev/ttyACM0": Device or resource busy
Eavrdude: butterfly_recv(): programmer is not responding

The command I was using :

avrdude -v -P /dev/ttyACM0 -c avr109 -p atmega32u4 -U flash:w:program.hex:i

After some trials, I noticed that ModemManager was in fact stealing the access to ttyACM0, briefly when the ProMicro was reset, causing the problem.

The solution : sudo apt-get purge modemmanager


STC15L204 : v2, and Thingspeak

06/06/2014 Posted by admin

No big news regarding the STC15L204 code. I have just updated the schematic, I have simplified cabling the resistors, capacitors and the ds18b20 directly on the stc board and have made some ‘live’ tests with 2 sensors at home (one being outside, in the mailbox…).

Receiver is done via a Raspberry Pi, and data is sent to Thingspeak server.

To increase distance, nrf24l01 speed was lowered to 250kbps.

(Lire la suite…)

preliminary – on-going : zx81 om stm32f103

12/05/2013 Posted by admin

zx81 on stm32 mini v3

STM32F4 Discovery / MP3 / Libmad / SDCard / USB-ouput / ChibiOS 2.6.1

11/08/2013 Posted by admin

Just an update for ChibiOS 2.6.1 of the code I have to run Libmad on the STM32F4 Discovery board.



Playing with STC15L204 : memory layout / IAP&EEPROM

09/17/2013 Posted by admin

Well, the STC15L204 data-sheet is not very clear on some aspects (the device is simple enough to compensate…).

I almost totally forgot that this device had a 512 bytes E2PROM… And I also wanted to explore its memory to try to figure where ISP code could be located, thus I made a small program to dump the memory content , first using a code pointer (something like « ptr=(__code unsigned char *)addr; » ) and then using the IAP registers (and to get some output in the IAP section, I have put a write 0×55 at address 0×123).

Here are the results (only displaying lines that does not contain only 0xFF) :

On first run :

> Device ready
0000 02 00 13 32 FF FF FF FF FF FF FF 02 02 5F 12 00
0310 50 52 4F 4D 0D 0A 00 0D 0A 3E 20 45 4E 44 0D 0A
0FF0 FF FF FF FF FF FF FF FF FF 00 0B 00 54 00 A4 BD 



(Lire la suite…)

First tests with STC15L204 + NRF24L01 boards – SDCC code

06/10/2013 Posted by admin

I have been searching for low cost wireless boards in the past few months to interface with PIR detectors & temperature sensors to create a small wireless network at home, and I have found the following product :

on many (Chinese) websites (dx.com / wayengineer.com / etc…) for around $7 (includes the nrf24l01+ module).

I bought some (via www.wayengineer.com), and only found limited number of documents describing them (mostly the datasheet on stcmcu.com).

(Lire la suite…)

Add a console to Cisco Small Business SLM2008

02/27/2013 Posted by admin

I recently opened a SLM2008 and noticed the unpopulated header with two signal lines : looked like a RS232 header.

Browsing the web (Maxim Integrated’s website) , I found a device that could be used for the unpopulated U11 : Max3243 (exact part could be another one, as I am not sure for pins 21/22 & 23, but I only really care about the TX/RX pins). On this part, there is a RS232-to-TTL between pins 6&17 and opposite TTL-to-RS232 between 13&10.

I quickly added wires on those pins :


And the ‘bus pirate’ on the header.

(Lire la suite…)

The weakest link in a Dell PE180AS KVM

02/27/2013 Posted by admin

This one is a bit outdated (March 2009), but I have found these photos back.

At the time, I had a problem with a Dell KVM that was no more working (no/bad video output, no more control over the KVM from the keyboard, etc…), and after asking the support about how much it would cost to have it fixed (which was the equivalent of buying a new one !), I decided to open it and try to fix it myself.




(Lire la suite…)