Connect One Ethernet shield

[HenrikOlsson]

Hi,
I had decided not to stick my nose into this but I'm going to anyway....
What are the reasons for not using the USART pins but instead using some ordinary I/O pins for serial in and out? The USARTs RX and TX pins are on 00 and 01 on the AMICUS18 which is what this forum section is about. Taking a quick look at the XINO Basic it TOO lists pins 00 and 01 as the USART RX and TX pins when used with the PICAXE chips listed there.

The PICAXE28X2 is just an 18F25K22 with some firmware so it TOO has the USART pins on RC6 and RC7 which then connects to pins 0 and 1. The AMICUS18 uses the 25K20 which also have the USART on RC6 and RC7.

Are these devices (nanoSocketLAN) not meant to be connected directly to a microcontroler with an USART thus expecting "true" data? Is the reason for not using the USART that they expect inverted data (I can't imagine that) and therfor you are using plain I/O and bit-banged serial where the polarity can be inverted instead of the microcontrolers onbaord USART?

I know you're providing pads so it can be re-wired but there must be a very specific reason for not wiring RX and TX to microcontrolers USART where they belong.

/Henrik.

[mackrackit]

The ConnectOne uses TRUE mode.
I like to leave the USART open for interruptible input to the MCU.

[dhouston]

I know you're providing pads so it can be re-wired but there must be a very specific reason for not wiring RX and TX to microcontrolers USART where they belong..

It's mostly because the various bootloaders are coded to use the hardware USART. And, I tend to think of these as development systems for READ (Rapid Embedded Application Development) where there will be a lot of changes, trials, errors, etc. rather than as finished products that stand on their own although they can certainly be used that way, as well.

DISCLAIMER: This thread and the Tibbo thread were not intended to disparage your WizNET approach. I'm just of the opinion that most folk are as lazy as me and use various Basic dialects so they don't have to learn ASM, C, etc. In that vein, both the ConnectOne and Tibbo modules do most of the heavy lifting that you're doing with SPI in your thread, making life easier for those of us inclined to take the easy way out. The Tibbo module requires coding but it's all in another Basic dialect and gets loaded as firmware into the Tibbo module rather than using much code space in the MCU be it PIC, PICAXE, Arduino AVR, or ZBasic AVR. And, it was fairly easy to design the shields so all the various modules (except for the 4 Mb flash) are plug-ins - no soldering required (I suspect the Tibbo & ConnectOne shields will have the SMT components preinstalled.)

[dhouston]

you are using plain I/O and bit-banged serial where the polarity can be inverted instead of the microcontrolers onbaord USART?

Ahh, methinks you presume too much.

On the rare occasions when I use a PIC bigger than the 8-pinners, I use ones where the comparator inputs and outputs are exposed. I use them as inverters for TX & RX. (@Bruce: On the 16F88, this uses up 6 pins so I'm just barely violating my 8-pin limit.) Most of the PICs, PICAXEs discussed in relation to these shields qualify and the Xino designers have agreed to look into making this optional in the DS30 bootloader. You only need current limiting resistors in TX & RX and it looks easy to add these to most of the Arduino clone main boards I've seen.

[dhouston]

What are the reasons for not using the USART pins but instead using some ordinary I/O pins for serial in and out?

Henrik,

Looks like I need to rephrase my previous response.

I had assumed PICAXE was using the hardware USART to download their program. While reading their user manual, I learned they are instead using SerIn/SerOut (i.e. software UART) for downloading and recommend leaving it free to avoid false triggers or interference with downloads. I will modify the ConnectOne and Tibbo shields, accordingly.

[mackrackit]

An EEPROM sample can be found here.
http://www.picbasic.co.uk/forum/show...461#post104461

[dhouston]

I have made some changes in order to use this with my Zarduino system boards. In addition to rerouting the I2C bus and RESET lines, I have also modified it to work with 3V3 or 5V but only when using the default serial connection. You can use SPI, USB or RMII with 3V3 but will need to do your own level shifting for 5V (which is not very practical).