Allow transfers greater than 255 bytes

[johnnyman727]

Currently, tessel-export.js disallows any transfers more than 255 bytes. This is constrained by the SPI Bridge implementation on the SAMD21.

The easiest fix would be to implement a queue in tessel-export.js and keeps track of outgoing/incoming packets. We would only send 255 bytes at at time, wait for the 255 byte response, then send the next 255.

[rwaldron]

Can you describe the issue that ambient/ir is hitting?

[johnnyman727]

Yes, Ambient and IR have a dependency on avr-isp which is reponsible for updating the module when it has old firmware.

As part of the updating process, it will try to send a multiple kB image over SPI but because that image is over 255 bytes, we get an error:

➜  t2-dem  t2 run node_modules/ambient-attx4/examples/ambient.js --name Hangy --lan
INFO Looking for your Tessel...
INFO Connected to Hangy over LAN
INFO Writing examples/ambient.js to RAM on Hangy (275.968 kB)...
INFO Deployed.
INFO Running examples/ambient.js...
Could not retrieve firmware version and module ID. Attempting update.
Uploading new firmware...
/usr/lib/node/tessel-export.js:378
    throw new RangeError('Buffer size must be within 1-255');
    ^

RangeError: Buffer size must be within 1-255
    at Tessel.Port._txrx (/usr/lib/node/tessel-export.js:378:11)
    at Tessel.SPI.transfer (/usr/lib/node/tessel-export.js:725:14)
    at ISP._transfer (/tmp/remote-script/node_modules/attiny-common/node_modules/avr-isp/index.js:540:12)
    at ISP._flashAll (/tmp/remote-script/node_modules/attiny-common/node_modules/avr-isp/index.js:275:10)
    at /tmp/remote-script/node_modules/attiny-common/node_modules/avr-isp/index.js:263:18
    at null.<anonymous> (/tmp/remote-script/node_modules/attiny-common/node_modules/avr-isp/index.js:371:9)
    at null.<anonymous> (/usr/lib/node/tessel-export.js:198:31)
    at emitNone (events.js:67:13)
    at Socket.emit (events.js:166:7)
    at emitReadable_ (_stream_readable.js:411:10)

[rwaldron]

Interesting! Thanks for the details :)

[kevinmehall]

Support for this on send was added here: 9c1222c

That would be fairly easy to adapt to use in _rx and _txrx as well. It doesn't have to wait for the response before sending the next chunk.

I'd also guess that .send could be used instead of transfer in the case of the firmware write.

[johnnyman727]

Thanks, @kevinmehall. Started implementation in #115.

[huseyinkozan]

#115 is closed, so will this ?

[rwaldron]

Yep! Thanks again for the follow up