smart pins and events
ManAtWork
Posts: 2,075
in Propeller 2
Today I tried talking to an absolute encoder of a servo motor from Sanyo Denki. It has a rather strange protocol, an asynchronous serial RS485 line (bi-directional half duplex) but with 16 bit frames instead of 8 and a CRC3 for sending and CRC8 for receiving with non-standard polynomials. So it's a good test for the capabilities of the P2.
Everything went surprisingly well and I got answers from the encoder on the fist go. However, I've noticed that the received words were somhow shifted. I got the first data word in place of the second, the second in the third and the first (status) contained garbage. I found out that the first WAITSE didn't work and fell through immediately. So I tried out some things and found out that the IN bit of the smartpin seems not to be reset by a DIR=0. If I insert an AKPIN and a POLLSE the WAITSE works as expected.
Is this normal behaviour or have I done something wrong? No big problem but I think it should be documented.
Everything went surprisingly well and I got answers from the encoder on the fist go. However, I've noticed that the received words were somhow shifted. I got the first data word in place of the second, the second in the third and the first (status) contained garbage. I found out that the first WAITSE didn't work and fell through immediately. So I tried out some things and found out that the IN bit of the smartpin seems not to be reset by a DIR=0. If I insert an AKPIN and a POLLSE the WAITSE works as expected.
drvl #pinEncTe fltl #pinEncTx ' reset smartpin wrpin mode_stx,#pinEncTx ' synchronous serial transmit wxpin baud_bits,#pinEncTx ' 2.5MBd 16N1 drvl #pinEncTx ' enable TX smartpin fltl #pinEncRx ' reset smartpin wrpin mode_srx,#pinEncRx ' synchronous serial receive wxpin baud_bits,#pinEncRx ' 2.5MBd 16N1 ' don't enable RX smartpin, it'd read TX data (loopback) setse2 #%001_000000 + pinEncRx ' IN rises txLoop drvh #pinEncTe waitx bitTime ' output enable delay wypin cmdCDF1,#pinEncTx ' start transmission waitx bitTime ' busy flag is not valid before start bit out .busy rqpin rxd,#pinEncTx wc ' read busy flag -> C if_c jmp #.busy ' wait for TX complete waitx bitTime drvl #pinEncTe drvl #pinEncRx ' enable RX smartpin akpin #pinEncRx ' force IN low pollse2 ' purge false event waitse2 rdpin status,#pinEncRx shr status,#16 waitse2 rdpin pos,#pinEncRx ' receive pos LSW shr pos,#16 waitse2 rdpin rxd,#pinEncRx ' receive pos MSB + CRC shr rxd,#16 and rxd,#$FF shl rxd,#16 or pos,rxd ' merge MSB+LSW to 24 bits getct time setq #2 wrlong pos,ptra ' write pos + time waitx cycleTime jmp #txLoop ' %AAAA_BBBB_FFF_PPPPPPPPPPPPP_TT_MMMMM_0 mode_stx long %0000_0000_000_0000000000000_01_11110_0 mode_srx long %0000_0000_000_0000000000000_00_11111_0 baud_bits long $10000*72 + 15 ' 2.5MBd 16N1 ' CRC CC EA FC SC cmdCDF1 long %100_00001_000_00_010 cycleTime long 18000 ' 1ms bitTime long 72 pos long 0 time long 0 errCnt long 0 rxd res 1 status res 1And BTW, the busy flag for sending is also undefined directly after starting a transmission. I have to wait some time before polling it, otherwise the busy flag polling loop is terminated immediately.
Is this normal behaviour or have I done something wrong? No big problem but I think it should be documented.
Comments
If you place the SETSE2 after the AKPIN then the POLLSE2 can probably be removed.